CN118020194A - Lithium secondary battery - Google Patents
Lithium secondary battery Download PDFInfo
- Publication number
- CN118020194A CN118020194A CN202280065721.3A CN202280065721A CN118020194A CN 118020194 A CN118020194 A CN 118020194A CN 202280065721 A CN202280065721 A CN 202280065721A CN 118020194 A CN118020194 A CN 118020194A
- Authority
- CN
- China
- Prior art keywords
- positive electrode
- active material
- battery
- electrode plate
- lithium secondary
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
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- 239000010703 silicon Substances 0.000 claims description 14
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- ACFSQHQYDZIPRL-UHFFFAOYSA-N lithium;bis(1,1,2,2,2-pentafluoroethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)C(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)C(F)(F)F ACFSQHQYDZIPRL-UHFFFAOYSA-N 0.000 description 1
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Abstract
The present invention discloses a lithium secondary battery, comprising: an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction; a battery can accommodating the electrode assembly; and a sealing body for sealing the open end of the battery can. The positive electrode plate contains a positive electrode active material that contains single particles or quasi-single particles having an average particle diameter D 50 of 5 [ mu ] m or less.
Description
Technical Field
The present application claims priority from korean patent application No. 10-2021-0136709, 10-2022-0049184, and 10-2022-011173, 2022-9-23, filed in korea on 10-14, 2021, and 20, respectively, both of which are incorporated herein by reference in their entirety.
The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery to which a positive electrode active material including single particles or quasi-single particles is applied so as to achieve excellent thermal stability even if the volume is increased.
Background
With the development of technologies such as electric vehicles and portable electronic devices, the demand for lithium secondary batteries as energy sources has rapidly increased.
Lithium secondary batteries are classified into can-type batteries, such as cylindrical or prismatic batteries, and pouch-type batteries according to the shape of a battery case. Among these batteries, can-type batteries are manufactured by covering and sealing the top of a battery can with a cap plate after accommodating a jelly-roll-type electrode in the battery can. The jelly-roll type electrode is manufactured by stacking a sheet-shaped positive electrode plate, a separator, and a negative electrode plate in order, and then winding the stack in one direction. The strip-shaped positive electrode lugs and the strip-shaped negative electrode lugs are respectively arranged in the positive plate and the negative plate. The positive electrode tab and the negative electrode tab are connected to the electrode terminal, thereby being electrically connected to an external power source. For reference, the positive terminal is a cap plate and the negative terminal is a battery can. However, in the can-type battery having the above-described structure of the related art, current is concentrated on the bar-shaped electrode tab, and thus resistance increases, a large amount of heat is generated, and current collecting efficiency deteriorates.
Meanwhile, with the progress of automobile technology in recent years, the demand for high-capacity batteries is also increasing. Therefore, development of a large-sized battery with a large volume is required. In small cylindrical batteries commonly used in the prior art (i.e., cylindrical batteries having a form factor of 1865 or 2170), the capacity is small, and thus resistance or heat generation does not have a significant effect on the battery performance. However, when the specification of the small-sized battery in the related art is directly applied to the large-sized battery, serious battery safety problems may occur.
As the size of the battery increases, the amount of heat and gas generated inside the battery also increases. The temperature and pressure inside the battery increase due to heat and gas, and the battery may fire or explode. To prevent this, the heat and gas inside the battery must be properly discharged to the outside. Therefore, the sectional area of the battery, which is a passage for discharging heat to the outside of the battery, must be increased as the volume increases. However, since the increase in the sectional area is generally smaller than the increase in volume, the amount of heat generated inside the battery increases as the battery becomes larger. Therefore, the risk of explosion increases, and the output deteriorates. Also, when rapid charge is performed at a high voltage, a large amount of heat is generated around the electrode tab in a short time, and the battery may be ignited.
Therefore, in order to achieve high capacity, it is necessary to develop a battery that exhibits high safety while having a large volume.
Disclosure of Invention
Technical problem
In order to solve the above problems, the present invention provides a lithium secondary battery in which single particles and/or quasi-single particles are contained as a positive electrode active material, and excellent thermal stability can be achieved even if the battery volume is increased.
Technical proposal
According to one example, the present invention provides a lithium secondary battery comprising: an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction; a battery can accommodating the electrode assembly; and a sealing body sealing an open end of the battery can, wherein the positive electrode plate comprises a positive electrode active material layer comprising a positive electrode active material having an average particle diameter D 50 μm or less and comprising single particles, quasi-single particles, or a combination thereof. The single particles and/or quasi-single particles may be present in an amount of 95 to 100 wt%, preferably 98 to 100 wt%, more preferably 99 to 100 wt%, based on the total weight of the positive electrode active material present in the positive electrode active material layer.
The positive electrode active material layer may contain a positive electrode active material having a unimodal particle size distribution that exhibits a unimodal in a volume cumulative particle size distribution map.
Further, the positive electrode active material may contain a lithium-containing nickel oxide containing 80mol% or more of Ni based on the total mole number of transition metals, and for example, may contain a lithium-nickel-based oxide represented by the following chemical formula 1:
li aNibCocM1 dM2 eO2..
Wherein in chemical formula 1, M 1 is at least one selected from the group consisting of Mn and Al, M 2 is at least one selected from the group consisting of Zr, W, ti, mg, ca, sr and Ba, 0.8.ltoreq.a.ltoreq. 1.2,0.83.ltoreq.b <1,0< c <0.17,0< d <0.17, 0.ltoreq.e.ltoreq.0.1.
Further, the primary particle diameter of the positive electrode active material may be 0.5 μm to 5 μm.
Meanwhile, the negative electrode plate may include a silicon-containing negative electrode active material.
In addition, the negative electrode plate may include a silicon-containing negative electrode active material and a carbon-containing negative electrode active material. Here, the silicon-containing anode active material and the carbon-containing anode active material may be provided in a weight ratio of 1:99 to 20:80.
Meanwhile, the secondary battery may be a cylindrical battery having a shape factor ratio of 0.4 or more, and may be, for example, 46110 battery, 4875 battery, 48110 battery, 4880 battery, or 4680 battery.
In addition, in the secondary battery of the present invention, each of the positive electrode plate and the negative electrode plate may include an uncoated portion where the active material layer is not formed. The cylindrical lithium secondary battery may be a battery having an electrode tab structure in which at least a portion of a positive electrode plate or a negative electrode plate without a coating portion defines an electrode tab.
The positive electrode plate uncoated portion and the negative electrode plate uncoated portion may be disposed along a positive electrode plate-side end and a negative electrode plate-side end, respectively, parallel to a direction in which the electrode assembly is wound. The current collecting plate may be coupled to each of the positive electrode plate uncoated portion and the negative electrode plate uncoated portion, and the current collecting plate may be connected to the electrode terminal.
Meanwhile, the positive and negative electrode plate uncoated portions may be processed in the form of a plurality of sections that are independently bendable, and at least a portion of the plurality of sections may define the electrode tab and be bent toward the winding center C of the electrode assembly. Further, at least a portion of the plurality of curved sections may overlap with upper and lower ends of the electrode assembly, and the collector plate may be combined with the overlapping plurality of sections.
Meanwhile, on the positive electrode plate, an insulating layer may be further provided that covers a portion of the positive electrode active material layer and a portion of the uncoated portion in a direction parallel to the winding direction.
According to another example, the present invention provides: a battery pack comprising the lithium secondary battery of the present invention; an automobile comprising the battery pack.
Advantageous effects
In the lithium secondary battery of the present invention, single particles and/or quasi-single particles are contained as the positive electrode active material, and thus gas generated due to particle breakage at the time of manufacturing the battery and internal cracks generated during charge and discharge can be minimized. Therefore, even in a large battery with an increased volume, excellent safety can be achieved.
Further, in the lithium secondary battery of the present invention, single particles and/or quasi-single particles contained in the positive electrode active material having an average particle diameter D 50 μm or less and a single-peak particle diameter distribution may be used, and thus an increase in resistance due to the application of the single particles or the quasi-single particles may be minimized. Thus, excellent capacity characteristics and output characteristics can be achieved.
Further, in the lithium secondary battery of the present invention, a silicon-containing anode active material having a large capacity may be contained as the anode active material. In this case, a higher energy density can be achieved.
In addition, the lithium secondary battery of the present invention may have no separate electrode tab, and may have a tab-less structure in which the positive electrode plate non-coating portion and the negative electrode plate non-coating portion serve as electrode tabs. For the battery in the related art in which the electrode tab is formed, a large amount of current is concentrated on the electrode tab during charging, and thus a large amount of heat is generated around the electrode tab. In particular, this phenomenon is more serious during rapid charge, and thus there is a risk of the battery firing or exploding. On the other hand, in the lithium secondary battery having the electrode tab structure of the present invention, the uncoated portion without the active material layer is formed at the end portion of each of the positive electrode plate and the negative electrode plate. The uncoated portion is connected to the electrode terminal by being attached to a collector plate having a large cross-sectional area. Compared with the battery with the electrode tab in the prior art, the battery with the electrodeless tab structure has less current concentration, so that the heat generation in the battery can be effectively reduced. Therefore, the thermal stability of the battery can be improved.
Drawings
Fig. 1 is a view showing a stacked state of an electrode assembly according to the present invention before being wound.
Fig. 2 is a sectional view illustrating an electrode plate structure of an electrode assembly according to an embodiment of the present invention.
Fig. 3 is a sectional view showing the structure of a battery having an electrodeless ear structure according to an embodiment of the present invention.
Fig. 4 is a sectional view showing the structure of a battery having an electrodeless ear structure according to another embodiment of the present invention.
Fig. 5 is a graph showing the hot box test results of the lithium secondary batteries of examples 1 and 2.
Fig. 6 is a graph showing the hot box test results of the lithium secondary battery of comparative example 1.
Fig. 7 is a view illustrating the structure of an electrode assembly according to an embodiment of the present invention.
Fig. 8 is a view illustrating a battery pack according to an embodiment of the present invention.
Fig. 9 is a diagram illustrating an automobile including a battery pack according to an embodiment of the present invention.
Detailed Description
Hereinafter, the present invention will be described in more detail.
The terms or words used in the present specification and claims should not be interpreted restrictively as ordinary meanings or dictionary-based meanings, but interpreted as meanings and concepts conforming to the technical spirit of the present invention based on the principle that the inventor can properly define the concept of terms to describe and explain the invention in the best mode.
In the present invention, "primary particles" means particle units having no observable grain boundaries when observed in a field of view of 5000 to 20000 times using a scanning electron microscope or a back-scattered electron diffractometer (Electron Back Scatter Diffraction; EBSD). The "average particle diameter of primary particles" means an arithmetic average value obtained by measuring and calculating the particle diameter of primary particles observed in a scanning electron microscope image.
In the present invention, the "secondary particles" are particles formed by aggregation of a plurality of primary particles. In the present invention, in order to distinguish from secondary particles formed by aggregation of several tens to several hundreds of primary particles in the related art, secondary particles in which 10 or less primary particles are aggregated are called quasi-single particles.
In the present invention, "average particle diameter D 50" means a particle diameter of 50% based on the volume cumulative particle diameter distribution of the positive electrode active material powder, and can be measured by using a laser diffraction method. For example, the positive electrode active material powder is dispersed in a dispersion medium, and then put into a commercial laser diffraction particle diameter measuring instrument (for example, microtrac MT 3000), and irradiated with ultrasonic waves having a frequency of about 28kHz and an output of 60W, to obtain a volume cumulative particle diameter distribution map. The average particle diameter D 50 can then be measured by calculating the particle diameter corresponding to 50% of the volume accumulation.
In the present invention, "consisting essentially of a" is meant to include the a component as well as any unrecited components that do not materially affect the basic and novel characteristics of this invention. The basic and novel features of the present invention include at least one of minimizing particle breakage during cell fabrication, minimizing gas generation from such particle breakage, and minimizing internal crack generation. In the context of such properties, the substantial impact is explained by the skilled person.
In one embodiment of the present invention, the single particles, the quasi-single particles, or a combination thereof may be present in an amount of, for example, 95 to 100 wt%, preferably 98 to 100 wt%, more preferably 99 to 100 wt%, based on the total weight of the positive electrode active material present in the positive electrode active material layer.
As a result of repeated studies to develop a large-sized battery having excellent safety while exhibiting high capacity, the present inventors found that safety of the large-sized battery can be significantly improved by using a quasi-single-particle positive electrode active material having single particles composed of one primary particle and/or aggregates of 10 or less primary particles as the positive electrode active material in one embodiment. Thus, the embodiments of the present invention have been completed.
Specifically, the lithium secondary battery of the present invention comprises: an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction; a battery can accommodating the electrode assembly; and a sealing body sealing the open end of the battery can. The positive electrode plate comprises a positive electrode active material layer, and the positive electrode active material layer comprises a positive electrode active material containing single particles and/or quasi-single particles with an average particle diameter D 50 [ mu ] m or less.
Electrode assembly
The electrode assembly has a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction. For example, the electrode assembly may be a jelly-roll type electrode assembly.
Fig. 1 illustrates a stacked structure of an electrode assembly of the present invention before being wound, and fig. 2 illustrates a cross-sectional structure of an electrode plate (positive or negative plate) of the present invention.
Referring to fig. 1 and 2, the electrode assembly of the present invention may be manufactured by winding a stack formed by sequentially stacking a separator 12, a positive electrode plate 10, a separator 12, and a negative electrode plate 11 at least once in one direction X.
Here, each of the positive electrode plate 10 and the negative electrode plate 11 has a structure as shown in fig. 2, in which an active material layer 21 is formed on a sheet-shaped current collector 20, and a partial region of the current collector 20 may have an uncoated portion 22 where the active material layer 21 is not formed.
As described above, when the positive electrode plate 10 and the negative electrode plate 11 including the non-coating portion 22 are used, a battery of an electrodeless ear structure without separate electrode ears can be realized in which at least a portion of the non-coating portion of the positive electrode plate 10 and the negative electrode plate 11 defines the electrode ears.
Specifically, uncoated portion 22 may be formed at an end portion of one side of current collector 20, extending along winding direction X. The current collector plate is connected to the electrode terminal by being bonded to the uncoated portion of the positive electrode plate and the uncoated portion of the negative electrode plate. Thus, a battery having an electrodeless ear structure can be obtained.
For example, a battery having an electrodeless ear structure may be manufactured by the following method. First, the separator, the positive electrode plate, the separator, and the negative electrode plate are sequentially stacked such that the uncoated portions 22 of the positive electrode plate 10 and the negative electrode plate 11 are located in opposite directions, and then stacked in one direction to manufacture an electrode assembly. Then, the uncoated portions 22 of the positive and negative electrode plates are bent in a direction toward the winding center C, and then the current collecting plates are welded and bonded to each of the uncoated portions of the positive and negative electrode plates. The collector plate is connected to the electrode terminal, and thus a battery having an electrodeless ear structure can be manufactured. Meanwhile, the collector plate has a larger sectional area than the strip-shaped electrode tab, and the resistance is inversely proportional to the sectional area of the current flowing path. Therefore, when the secondary battery of the above-described structure is formed, the battery resistance can be significantly reduced.
Meanwhile, the positive and negative electrode plate uncoated portions may be processed in the form of a plurality of sections that are independently bendable, and at least a portion of the plurality of sections may be bent toward the winding center C of the electrode assembly.
The segments may be formed by processing the current collectors of the positive and negative plates through metal foil cutting processes such as laser grooving, ultrasonic cutting, and stamping.
When the uncoated portions of the positive and negative electrode plates are processed in the form of a plurality of segments, the stress acting on the uncoated portions at the time of bending can be reduced to prevent deformation or damage of the uncoated portions, thereby improving the welding characteristics with the current collector plate.
The current collector plate and the uncoated portion are generally bonded to each other by welding, and in order to enhance the welding characteristics, the uncoated portion may be bent as uniformly as possible by applying a strong pressure to the welding surface of the uncoated portion. However, during this bending, the shape of the uncoated portion may be irregularly distorted and deformed. The deformed region may contact the electrode of opposite polarity, resulting in internal shorting or microcracking of the uncoated portion. However, when the uncoated portions of the positive and negative electrode plates are processed in the form of a plurality of sections that are independently bendable, the stress acting on the uncoated portions during bending can be relieved, thereby minimizing deformation and damage of the uncoated portions.
Further, when the uncoated portion is processed into a segment form as described above, the plurality of segments overlap each other during bending, thereby increasing the welding strength with the collector plate. When advanced techniques such as laser welding are used, laser light may penetrate into the electrode assembly and prevent problems of melting and evaporation of the separator or active material. Preferably, at least a portion of the plurality of curved sections may overlap with upper and lower ends of the electrode assembly, and the collector plate may be combined with the overlapping plurality of sections.
Meanwhile, the electrode assembly of the present invention may have a structure in which an insulating layer 24 is further formed on the positive electrode plate 10 as shown in fig. 7. Specifically, the insulating layer 24 may be formed to cover a portion of the positive electrode active material layer 21c and a portion of the uncoated portion in a direction parallel to the winding direction of the electrode assembly.
In the case of a battery of an electrode tab-less structure in which the uncoated portion 22c of the positive electrode plate 10 and the uncoated portion 22a of the negative electrode plate 11 serve as electrode tabs, the electrode assembly is formed such that the positive electrode plate 10 may protrude upward from the separator 12, the negative electrode plate 11 may protrude downward from the separator 12, and the protruding positive electrode plate 10 and/or negative electrode plate 11 may be bent and then coupled to the current collecting plate. However, when positive electrode plate 10 or negative electrode plate 11 is bent as described above, the current collector of positive electrode plate 10 or negative electrode plate 11 passes over the separator and approaches the electrode of the opposite polarity. Therefore, there is a possibility that the positive electrode plate and the negative electrode plate are in electrical contact with each other and cause internal short circuits. However, when the insulating layer 24 covering the positive electrode active material layer and a portion of the non-coating portion is formed, as shown in fig. 7, the insulating layer 24 may prevent the positive electrode plate 10 and the negative electrode plate 11 from electrically contacting each other, thereby preventing the occurrence of a short circuit inside the battery.
Preferably, the insulating layer 24 may be disposed on at least one surface of the current collector of the positive electrode plate 10, and preferably, may be disposed on both surfaces of the positive electrode plate 10.
Further, the insulating layer 24 may be formed in a region of the positive electrode plate 10 that may face the active material layer 21a of the negative electrode plate 11. For example, on the surface of positive electrode plate 10 that faces negative electrode plate 11 after uncoated portion 22c is bent, insulating layer 24 may be formed to extend to the distal end of uncoated portion 22 c. However, for the surface opposite to the surface facing the negative electrode plate 11 after bending, it is desirable that the insulating layer 24 is formed only in a part of the uncoated portion 22c, for example, before reaching the bending point of the uncoated portion 22 c. This is because, when the insulating layer 24 is formed on the entire area on the surface of the uncoated portion opposite to the surface facing the negative electrode plate 11, it cannot be in electrical contact with the collector plate, and therefore the uncoated portion cannot be used as an electrode tab.
Meanwhile, the material or composition of the insulating layer 24 is not particularly limited as long as it can be attached to the positive electrode plate while securing insulating properties. For example, the insulating layer may be an insulating coating or an insulating tape, and the insulating coating may contain an organic binder and inorganic particles. Here, the organic binder may be, for example, styrene-butadiene rubber (SBR), and the inorganic particles may be alumina, but is not limited thereto.
Hereinafter, each component of the electrode assembly of the present invention will be described in detail.
(1) Positive plate
The positive electrode plate may have a structure in which a positive electrode active material layer is formed on one surface or both surfaces of a sheet-shaped positive electrode collector, and the positive electrode active material layer may include a positive electrode active material, a conductive material, and a binder.
Specifically, the positive electrode slurry is manufactured by dispersing a positive electrode active material, a conductive material, and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and water. The positive electrode slurry is coated on one surface or both surfaces of a sheet-shaped positive electrode current collector, and the solvent in the positive electrode slurry is removed by a drying process. Then, the positive electrode plate may be manufactured through a rolling process. Meanwhile, during the application of the positive electrode slurry, the positive electrode slurry is not applied to a partial region of the positive electrode current collector, for example, one end of the positive electrode current collector. Thus, a positive electrode plate having an uncoated portion can be manufactured.
Various positive electrode collectors used in the art may be used as the positive electrode collector. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like may be used as the positive electrode current collector. The positive electrode collector may have a typical thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode collector, thereby improving the adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, for example, films, sheets, foils, nets, porous structures, foams and non-woven fabrics.
In the present invention, the positive electrode active material has single particles made of single primary particles and/or quasi-single particles as aggregates of 10 or less primary particles.
According to the related art, spherical secondary particles in which tens to hundreds of primary particles are aggregated are generally used as a positive electrode active material of a lithium secondary battery. However, with the above-described secondary particle type positive electrode active material having many primary particles agglomerated, during the production of the positive electrode, particle breakage occurs during the roll process, and primary particles are detached. In addition, cracks are generated inside the particles during the charge and discharge. When particle breakage of the positive electrode active material or crack inside the particles occurs, the contact area with the electrolyte increases. Therefore, the gas generated due to the side reaction with the electrolyte increases. As the gas generated inside the battery increases, the pressure inside the battery increases. Therefore, there is a risk of explosion of the battery. In particular, when the volume of the cylindrical battery increases, the amount of active material inside the battery also increases due to the increase in volume. Thus, the amount of gas generated also increases significantly, and thus the risk of the battery firing and/or explosion is higher.
On the other hand, the positive electrode active material having quasi-single particles having single particles made of primary particles and/or aggregation of 10 or less primary particles has higher particle strength than the existing positive electrode active material having a secondary particle type having aggregation of several tens to several hundreds of primary particles. Therefore, particle breakage hardly occurs during rolling. Further, for the positive electrode active material having single particles or quasi-single particles, the number of primary particles constituting the particles is small. Therefore, the change due to the volume expansion and contraction of the primary particles during the charge and discharge is small, thereby significantly reducing the occurrence of cracks inside the particles.
Therefore, when the positive electrode active material made of single particles and/or quasi-single particles is used as in the present invention, the amount of gas generation due to particle breakage and internal crack generation can be significantly reduced, and thus excellent safety can be achieved even in a large-sized battery.
Meanwhile, it is preferable that the single particle and/or quasi-single particle be present in the positive electrode active material in an amount of 95 to 100 wt%, preferably 98 to 100 wt%, more preferably 99 to 100 wt%, still more preferably 100 wt%, based on the total weight of the positive electrode active material present in the positive electrode active material layer. When the content of the single particles and/or the quasi-single particles satisfies the above range, sufficient safety can be obtained when applied to a large-sized battery. When the content of the positive electrode active material in the form of secondary particles exceeds 5wt% of the total positive electrode active material, side reactions with the electrolyte increase due to powder generated from the secondary particles during electrode manufacturing and charge and discharge, and the effect of suppressing gas generation decreases. Therefore, when applied to a large battery, the effect of improving stability may be reduced.
Meanwhile, the average particle diameter D 50 of the positive electrode active material of the present invention may be 5 μm, 4 μm, 3 μm or 2 μm or less, for example, 0.5 μm to 5 μm, preferably 1 μm to 5 μm, more preferably 2 μm to 5 μm. When the average particle diameter D 50 of the positive electrode active material satisfies this range of 5 μm or less, then an increase in resistance can be minimized.
In the positive electrode active material having single particles and/or quasi-single particles, the interface between the primary particles, which are lithium ion diffusion paths inside the particles, is small. Therefore, lithium mobility is reduced compared to a positive electrode active material having secondary particles, and thus resistance is increased. As the particle size increases, the resistance increases. When the resistance increases, both the capacity and the output characteristics are adversely affected. Therefore, in the present invention, a single-particle and/or quasi-single-particle positive electrode active material having an average particle diameter D 50 μm or less is used. Therefore, the diffusion distance of lithium ions inside the particles is minimized, and an increase in resistance can be suppressed.
In the positive electrode active material, the average particle diameter of the primary particles may be 5 μm, 4 μm, 3 μm or 2 μm or less, for example, 0.5 μm to 5 μm, preferably 1 μm to 5 μm, more preferably 2 μm to 5 μm. When the average particle diameter of the primary particles satisfies the range of 5 μm or less, a positive electrode active material having single particles and/or quasi-single particles exhibiting excellent electrochemical properties can be formed. When the average particle diameter of the primary particles is very small, the aggregation number of the primary particles forming the positive electrode active material becomes large, and the effect of suppressing occurrence of particle breakage during rolling is reduced. When the average particle diameter of the primary particles is very large, lithium diffusion paths in the primary particles become long, resistance may increase, and output characteristics may deteriorate.
In the present invention, it is preferable that the positive electrode active material contained in the positive electrode active material layer has a unimodal particle size distribution. According to the related art, a bimodal positive electrode active material has been widely used to increase the electrode density of a positive electrode active material layer. The large-particle-diameter positive electrode active material with larger average particle diameter and the small-particle-diameter positive electrode active material with smaller average particle diameter are mixed and used for the bimodal positive electrode active material. However, with the positive electrode active material having single particles or quasi-single particles as described above, as the particle diameter increases, the path of movement of lithium becomes long, and thus the resistance increases significantly. Therefore, when particles having a larger particle diameter are mixed for use, the capacity and output characteristics may be lowered. Accordingly, the positive electrode active material having a unimodal distribution is used in the present invention, and thus an increase in resistance can be minimized.
Meanwhile, the positive electrode active material may contain a lithium-containing nickel oxide, and in particular, may contain 80mol% or more of Ni based on the total mole number of transition metals. Preferably, the lithium nickel-based oxide may contain 80mol% or more and less than 100mol%, 82mol% or more and less than 100mol%, or 83mol% or more and less than 100mol% of Ni. When the lithium-containing nickel oxide containing a high Ni content is used as described above, a high capacity can be achieved.
More specifically, the positive electrode active material may include a lithium-containing nickel oxide represented by the following chemical formula 1.
Li aNibCocM1 dM2 eO2 [ chemical formula 1]
In chemical formula 1, M 1 may be one or more selected from the group consisting of Mn and Al, and is preferably Mn or Mn and Al.
M 2 may be one or more selected from the group consisting of Zr, W, Y, ba, ca, ti, mg, ta and Nb, preferably one or more selected from the group consisting of Zr, Y, mg and Ti, more preferably Zr, Y or a combination thereof. The element M 2 is not necessarily contained, but when an appropriate amount of the element M 2 is contained, it can be used to promote grain growth during firing or improve stability of crystal structure.
A represents the mole fraction of lithium in the lithium-containing nickel oxide, and a is more than or equal to 0.8 and less than or equal to 1.2,0.85 and less than or equal to 1.15, or a is more than or equal to 0.9 and less than or equal to 1.2. When the molar fraction of lithium satisfies this range of 0.8.ltoreq.a.ltoreq.1.2, the crystal structure of the lithium-containing nickel oxide can be stably formed.
B represents the mole fraction of nickel in all metals except lithium in the lithium-containing nickel oxide, and may satisfy 0.8.ltoreq.b <1,0.82.ltoreq.b <1, or 0.83.ltoreq.b <1. When the mole fraction of nickel satisfies this range of 0.8.ltoreq.b <1, high energy density occurs, and it is possible to achieve high capacity.
C represents the mole fraction of cobalt in all metals except lithium in the lithium-containing nickel oxide, and 0< c <0.2,0< c <0.18, or 0.01.ltoreq.c.ltoreq.0.17 may be satisfied. When the mole fraction of cobalt satisfies this range of 0< c <0.2, good resistance characteristics and output characteristics can be obtained.
D represents the mole fraction of M 1 element in all metals except lithium in the lithium-containing nickel oxide, and can satisfy 0< d <0.2,0< d <0.18, or 0.01.ltoreq.d.ltoreq.0.17. When the mole fraction of the element M 1 satisfies this range of 0< d <0.2, the structural stability of the positive electrode active material is excellent.
E represents the mole fraction of M 2 element in all metals except lithium in the lithium-containing nickel oxide, and can satisfy 0.ltoreq.e.ltoreq.0.1 or 0.ltoreq.e.ltoreq.0.05.
Meanwhile, the positive electrode active material of the present invention may further include a coating layer containing one or more coating elements selected from the group consisting of Al, ti, W, B, F, P, mg, ni, co, fe, cr, V, cu, ca, zn, zr, nb, mo, sr, sb, bi, si and S on the surface of the particles containing lithium nickel oxide, as needed. Preferably, the coating element may be Al, B, co or a combination thereof.
When a coating layer is present on the surface of the particles containing lithium nickel oxide, contact between the electrolyte and the lithium composite transition metal oxide is inhibited by the coating layer. Therefore, elution of transition metal or generation of gas due to side reaction with the electrolyte can be reduced.
The content of the positive electrode active material may be 80 to 99 wt%, preferably 85 to 99 wt%, more preferably 90 to 99 wt%, based on the total weight of the positive electrode active material layer.
The conductive material is used to impart conductivity to the electrode, and is not particularly limited as long as it has electron conductivity without causing chemical changes in the constituent battery. As specific examples, there may be: graphite, such as natural graphite and artificial graphite; carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fibers, and carbon nanotubes; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative. Wherein any one or a mixture of two or more may be used. The content of the conductive material may be generally 1 to 30 wt%, preferably 1 to 20 wt%, more preferably 1 to 10 wt%, based on the total weight of the positive electrode active material layer.
The binder serves to improve adhesion between the positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. As specific examples, there may be polyvinylidene fluoride (PVDF), vinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. Wherein any one or a mixture of two or more may be used. The content of the binder may be generally 1 to 30 wt%, preferably 1 to 20 wt%, more preferably 1 to 10 wt%, based on the total weight of the positive electrode active material layer.
Meanwhile, on the positive electrode plate of the present invention, an insulating layer for covering the positive electrode active material layer and a part of the uncoated portion may be further formed as needed. The insulating layer may be formed in a direction parallel to the winding direction of the electrode assembly.
(2) Negative plate
The negative electrode plate may have a structure in which a negative electrode active material layer is formed on one surface or both surfaces of a sheet-shaped negative electrode current collector, and the negative electrode active material layer may contain a negative electrode active material, a conductive material, and a binder.
Specifically, the anode slurry is manufactured by dispersing an anode active material, a conductive material, and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and water. The negative electrode slurry is coated on one surface or both surfaces of a sheet-shaped negative electrode current collector, and the solvent in the negative electrode slurry is removed through a drying process. Then, the negative electrode plate may be manufactured through a roll process. Meanwhile, during the application of the anode slurry, the anode slurry is not applied to a partial region of the anode current collector, for example, one end of the anode current collector. Thus, a negative electrode plate having an uncoated portion can be manufactured.
As the anode active material, a compound capable of reversibly intercalating and deintercalating lithium may be used. As specific examples of the anode active material, there may be: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers and amorphous carbon; silicon-containing materials such as Si, si-Me alloys (where Me is one or more selected from the group consisting of Al, sn, mg, cu, fe, pb, zn, mn, cr, ti and Ni), siO y (where 0< y < 2), and Si-C composites; a lithium metal thin film; and metal materials capable of forming alloys with lithium, such as Sn and Al. Wherein any one or a mixture of two or more may be used.
Preferably, the negative electrode plate of the present invention may include a silicon-containing negative electrode active material. The silicon-containing anode active material may be Si, a Si-Me alloy (where Me is one or more selected from the group consisting of Al, sn, mg, cu, fe, pb, zn, mn, cr, ti and Ni), siO y (where 0< y < 2), a Si-C composite, or a combination thereof, preferably SiO y (where 0< y < 2). The silicon-containing anode active material has higher theoretical capacity. Accordingly, when the silicon-containing anode active material is contained, the capacity characteristics can be enhanced.
Meanwhile, the silicon-containing anode active material may be doped with M b metal. Here, the M b metal may be a group 1 metal element or a group 2 metal element, and specifically, may be Li or Mg or the like. Specifically, the silicon anode active material may be Si doped with M b metal, siO y (where 0< y < 2), si—c composite, or the like. For a silicon-containing anode active material doped with a metal, the capacity of the active material is slightly reduced due to the doping element, but the efficiency becomes high. Thus, a high energy density can be achieved.
The silicon-containing anode active material may further include a carbon coating layer on the surface of the particles. Here, the amount of the carbon coating layer may be 20 wt% or less, preferably 1 wt% to 20 wt%, based on the total weight of the silicon-containing anode active material.
In addition, the negative electrode plate may further contain a carbonaceous negative electrode active material as a negative electrode active material, as required. The carbonaceous anode active material may be, for example, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or the like, but is not limited thereto.
Meanwhile, when a mixture of a silicon-containing anode active material and a carbon-containing anode active material is used as the anode active material, the mixing ratio of the silicon-containing anode active material and the carbon-containing anode active material may be 1:99 to 20:80, preferably 1:99 to 15:85, more preferably 1:99 to 10:90 (by weight).
The content of the anode active material may be 80 to 99 wt%, preferably 85 to 99 wt%, more preferably 90 to 99 wt%, based on the total weight of the anode active material layer.
Meanwhile, a negative electrode current collector commonly used in the art may be used as the negative electrode current collector. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper surface-treated with carbon, nickel, titanium, or silver, or stainless steel or an aluminum-cadmium alloy may be used. The thickness of the negative electrode current collector may be generally 3 μm to 500 μm, and similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to enhance the adhesion of the negative electrode active material. For example, various forms may be used, such as films, sheets, foils, nets, porous structures, foams and non-woven fabrics.
The conductive material is used to impart conductivity to the anode, and is not particularly limited as long as it has electron conductivity without causing chemical changes in the constituent battery. As specific examples, there may be: graphite, such as natural graphite and artificial graphite; carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fibers, and carbon nanotubes; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative. Wherein any one or a mixture of two or more may be used. The content of the conductive material may be generally 1 to 30 wt%, preferably 1 to 20 wt%, more preferably 1 to 10 wt%, based on the total weight of the anode active material layer.
The binder is used to improve adhesion between the anode active material particles and adhesion between the anode active material and the anode current collector. As specific examples, there may be polyvinylidene fluoride (PVDF), vinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. Wherein any one or a mixture of two or more may be used. The content of the binder may be generally 1 to 30 wt%, preferably 1 to 20 wt%, more preferably 1 to 10 wt%, based on the total weight of the anode active material layer.
(3) Diaphragm
The separator separates the anode and the cathode and provides a moving path of lithium ions, and is not particularly limited as long as it is generally used as a separator in a lithium secondary battery. Specifically, a porous polymer film such as a porous polymer film prepared from a polyolefin-based polymer (e.g., an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer) may be used as the separator, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of glass fiber or polyethylene terephthalate fiber or the like having a high melting point, may be used as the separator. In addition, in order to secure heat resistance or mechanical strength, a coated separator including a ceramic component or a polymer material may be used.
Lithium secondary battery
Next, the lithium secondary battery of the present invention will be described.
The battery of the present invention may comprise: an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction; a battery can accommodating the electrode assembly; and a sealing body sealing the open end of the battery can.
Preferably, the lithium secondary battery of the present invention may be a cylindrical battery, preferably a large cylindrical battery having a shape factor ratio of 0.4 or more (a value obtained by dividing the diameter of the cylindrical battery by the height, i.e., defined as the diameterRatio to height H). Here, the form factor means a value referring to the diameter and height of the cylindrical battery.
The cylindrical battery of the present invention may be, for example, 46110 battery (diameter 46mm, height 110mm, shape factor ratio 0.418), 4875 battery (diameter 48mm, height 75mm, shape factor ratio 0.640), 48110 battery (diameter 48mm, height 110mm, shape factor ratio 0.436), 4880 battery (diameter 48mm, height 80mm, shape factor ratio 0.600) and 4680 battery (diameter 46mm, height 80mm, shape factor ratio 0.575). Among the values representing the form factors, the first two numbers represent the diameter of the battery, and the last two or three numbers represent the height of the battery.
In the lithium secondary battery of the present invention, the positive electrode active material having single particles and/or quasi-single particles is applied, and thus the gas generation amount is significantly reduced as compared with the prior art. Therefore, even in a large cylindrical battery having a shape factor ratio of 0.4 or more, excellent safety can be achieved.
Meanwhile, the battery of the present invention may be a battery having an electrodeless ear structure not including an electrode tab, but is preferably not limited thereto.
The battery having the electrode tab structure may have a structure in which, for example, the positive electrode plate and the negative electrode plate each contain an uncoated portion where the active material layer is not formed. The positive electrode plate uncoated portion and the negative electrode plate uncoated portion are located at upper and lower ends of the electrode assembly, respectively. The current collector plate is bonded to each of the uncoated portion of the positive electrode plate and the uncoated portion of the negative electrode plate. The collector plate is connected to the electrode terminal.
Fig. 3 shows a cross-sectional view of a battery having an electrodeless ear structure in accordance with an embodiment of the present invention. Hereinafter, a cylindrical battery according to an embodiment of the present invention will be described with reference to fig. 3. However, fig. 3 shows only one embodiment of the present invention, and the structure of the battery of the present invention is not limited to the scope shown in fig. 3.
The battery 140 of the embodiment of the present invention includes a jelly-roll type electrode assembly 141, a battery can 142 accommodating the electrode assembly 141, and a sealing body 143 sealing an open end of the battery can 142.
Here, each of the positive and negative electrode plates of the electrode assembly may include an uncoated portion where the active material layer is not formed, and may be stacked and wound such that the positive and negative electrode plate uncoated portions are located at upper and lower ends of the electrode assembly, respectively. The electrode assembly has been described above, and therefore, hereinafter, only other components than the electrode assembly will be described.
The battery can 142 is a container formed with an opening at an upper side thereof, and is made of a conductive metal material such as aluminum or steel. The battery can accommodates the electrode assembly 141 in the inner space through the upper opening and together accommodates the electrolyte.
As the electrolyte used in the present invention, various electrolytes useful for lithium secondary batteries, such as an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-like polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, can be used. However, the type thereof is not particularly limited.
In particular, the electrolyte may include an organic solvent and a lithium salt.
The organic solvent is not particularly limited as long as it can serve as a medium for ion movement involved in the electrochemical reaction of the battery. Specifically, as the organic solvent, it is possible to use: ester solvents such as methyl acetate, ethyl acetate, gamma-butyrolactone or epsilon-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents, such as cyclohexanone; aromatic hydrocarbon-containing solvents such as benzene or fluorobenzene; carbonate solvents, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl Ethyl Carbonate (MEC), ethylene Carbonate (EC) or Propylene Carbonate (PC); alcohol solvents such as ethanol, isopropanol; nitriles, such as R-CN (wherein R is a linear, branched or cyclic C2-C20 hydrocarbon group, which may contain a double bond, an aromatic ring or an ether linkage); amides, such as dimethylformamide; dioxolanes, such as 1, 3-dioxolane; or sulfolane. Among them, a carbonate-based solvent is preferably used. More preferably, a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) and a low-viscosity linear carbonate compound (e.g., ethylene carbonate, dimethyl carbonate or diethyl carbonate) having high ionic conductivity and high dielectric constant to improve charge and discharge performance of the battery is used.
The lithium salt is not particularly limited as long as it is a compound capable of providing lithium ions for a lithium secondary battery. Specifically, LiPF6、LiClO4、LiAsF6、LiBF4、LiSbF6、LiAlO4、LiAlCl4、LiCF3SO3、LiC4F9SO3、LiN(C2F5SO3)2、LiN(C2F5SO2)2、LiN(CF3SO2)2、LiCl、LiI or LiB (C 2O4)2, etc. lithium salts may be used in a concentration range of 0.1M to 5.0M, preferably 0.1M to 3.0M. When the concentration of lithium salts is in a range of 0.1M to 5.0M, the electrolyte has suitable conductivity and viscosity. Thus, excellent electrolyte properties can be obtained, and lithium ions can migrate effectively.
In addition to these electrolyte components, the electrolyte may contain additives for improving the life characteristics of the battery, suppressing the decrease in the battery capacity, and improving the discharge capacity of the battery. For example, as the additive, halogenated alkylene carbonate compounds such as ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, N-glyme, hexamethylphosphoric triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, or the like may be used, and any one or a mixture thereof may be used. However, the additive is not limited thereto. The content of the additive may be 0.1 to 10 wt%, preferably 0.1 to 5 wt%, based on the total weight of the electrolyte.
The battery can 142 is electrically connected to the uncoated portion 146b of the negative electrode plate and is in contact with an external power source, serving as a negative electrode plate terminal for transmitting current applied by the external power source to the negative electrode plate.
A crimping portion 147 and a crimping portion 148 may be provided at the upper end of the battery can 142 as needed. The beading portion 147 may be formed by pressing the circumference of the outer circumferential surface of the battery can 142 by a distance D1. The beading portion 147 prevents the electrode assembly 141 received inside the battery can 142 from being separated through the upper opening of the battery can 142, and may serve as a support for the sealing body 143.
The crimp portion 148 may be formed above the beading portion 147 and have a shape that extends and bends to surround a portion of the outer circumferential surface of the cap plate 143a and a portion of the top surface of the cap plate 143a disposed above the beading portion 147.
Next, the sealing body 143 seals the open end of the battery can 142, and includes a cap plate 143a and a first gasket 143b providing air tightness and insulating properties to a space between the cap plate 143a and the battery can 142, and may further include a connection plate 143c electrically and mechanically coupled to the cap plate 143a as needed. The cap plate 143a may be pressed against the beading portion 147 formed in the battery can 142 and fixed by the crimp portion 148.
The cap plate 143a is a member made of a metal material having conductivity and covering an upper opening of the battery can 142. The cap plate 143a is electrically connected to the positive electrode plate of the electrode assembly 141, and is electrically insulated from the battery can 142 by the first gasket 143 b. Accordingly, the cap plate 143a may serve as a positive terminal of the secondary battery. The cover plate 143a may include a protrusion 143d protruding upward from the winding center C thereof. The protruding portion 143d contacts an external power source and allows current to be applied from the external power source.
The first gasket 143b may be interposed between the cap plate 143a and the crimp 148 to ensure the air tightness of the battery can 142 and the electrical insulation between the battery can 142 and the cap plate 143 a.
Meanwhile, the battery 140 of the present invention may further include current collecting plates 144 and 145 as needed. The collector plate is coupled to the positive electrode plate uncoated portion 146a and the negative electrode plate uncoated portion 146b, and is connected to electrode terminals (i.e., positive electrode terminal and negative electrode terminal).
Specifically, the battery 140 of the present invention may include a first collector plate 144 coupled to an upper portion of the electrode assembly 141 and a second collector plate 145 coupled to a lower portion of the electrode assembly 141.
A first collector plate 144 and/or a second collector plate 145 may also be included.
The first collector plate 144 is coupled to an upper portion of the electrode assembly 141. The first collector plate 144 may be made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the uncoated portion 146a of the positive electrode plate. Leads 149 may be connected to first collector plate 144. The lead 149 extends upward from the electrode assembly 141 and may be coupled to the connection plate 143c or directly coupled to the bottom surface of the cap plate 143 a. For example, bonding between the lead 149 and other components may be achieved by welding. Preferably, the first collector plate 144 may be integrally formed with the lead 149. In this case, the lead 149 may have a plate shape extending outward from the winding center C of the first collector plate 144.
Meanwhile, the first collector plate 144 is coupled to an end of the non-coating portion 146a of the positive electrode plate. Such bonding may be achieved by laser welding, resistance welding, ultrasonic welding, brazing, or the like.
The second collecting plate 145 is coupled to a lower portion of the electrode assembly 141. The second current collecting plate 145 may be made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the uncoated portion 146b of the negative electrode plate. One surface of the second current collecting plate 145 may be coupled to the non-coating portion 146b of the negative electrode plate, and the other surface may be coupled to the inner bottom surface of the battery can 142. Here, the bonding may be achieved by laser welding, resistance welding, ultrasonic welding, brazing, or the like.
Meanwhile, the battery 140 of the present invention may further include an insulator 146 as needed. Insulator 146 may be disposed to cover the top surface of first collector plate 144. The insulator 146 covers the first collector plate 144, and thus the first collector plate 144 and the battery can 142 can be prevented from directly contacting each other.
The insulator 146 includes a lead hole 151 through which a lead 149 extending upward from the first collector plate 144 may be led out. The lead 149 is coupled to the bottom surface of the connection plate 143c or the bottom surface of the cap plate 143a by being drawn upward through the lead hole 151.
The insulator 146 may be made of a polymer resin having an insulating property, such as a polymer resin material of polyethylene, polypropylene, polyimide, or polybutylene terephthalate.
Meanwhile, the battery 140 of the present invention may further include a vent 152 formed in the bottom surface of the battery can 142, as needed. The ventilation portion 152 corresponds to a region of the bottom surface of the battery can 142 having a smaller thickness than the peripheral region. The vent 152 is of a smaller thickness and therefore structurally weaker than the peripheral region. Therefore, when the pressure in the battery 140 rises above a certain level, the vent 152 breaks, and the gas in the battery can 152 is discharged to the outside, thereby preventing explosion of the battery.
Fig. 4 shows a cross-sectional view of a battery having an electrodeless ear structure in accordance with another embodiment of the present invention. Hereinafter, a cylindrical battery according to another embodiment of the present invention will be described with reference to fig. 4. However, fig. 4 shows only one embodiment of the present invention, and the structure of the battery of the present invention is not limited to the scope shown in fig. 4.
Referring to fig. 4, the cylindrical battery 170 according to another embodiment of the present invention has a different structure of a battery can and a sealing body than the battery 140 shown in fig. 3, but has substantially the same structure of an electrode assembly and an electrolyte.
Specifically, the battery 170 includes a battery can 171 through which rivet terminals 172 pass and are mounted. The rivet terminal 172 is mounted to a partially closed surface (upper surface in the drawing) of the battery can 171, which may be a first end of the battery can. The rivet terminal 172 is riveted in a through hole (a first opening of the first end) of the battery can 171 in a state in which the second gasket 173 having an insulating property is inserted therein. The rivet terminals 172 are exposed outwardly in a direction opposite to the direction of gravity.
The rivet terminal 172 includes a terminal exposing portion 172a and a terminal inserting portion 172b. The terminal exposing portion 172a is exposed outward from the closing surface of the battery case 171. The terminal exposing portion 172a may be located at a substantially winding center C of a partial closing surface of the battery can 171. The maximum diameter of the terminal exposing portion 172a may be formed to be larger than the maximum diameter of the through hole formed in the battery can 171. The terminal insertion portion 172b passes through the substantially winding center C of the partial closing surface of the battery can 171, and may be electrically connected to the non-coating portion 146a of the positive electrode plate. The terminal insertion part 172b may be riveted to the inner surface of the battery can 171. That is, the terminal insertion part 172b may have a shape bent toward the inner surface of the battery can 171. The maximum diameter of the end of the terminal insertion part 172b may be greater than the maximum diameter of the through hole of the battery can 171.
The lower end surface of the terminal insertion portion 172b may be welded to the first collector plate 144 connected to the non-coating portion 146a of the positive electrode plate. An insulating cover 174 made of an insulating material may be interposed between the first collector plate 144 and the inner surface of the battery can 171. The insulating cover 174 covers the upper portion of the first collector plate 144 and the upper end edge portion of the electrode assembly 141. Therefore, it is possible to prevent a short circuit from occurring when the uncoated portion of the outer circumference of the electrode assembly 141 contacts the inner surface of the battery can 171 having the different polarity. The terminal insertion portion 172b of the rivet terminal 172 passes through the insulating cover 174, and may be welded to the first collector plate 144.
The second gasket 173 is interposed between the battery can 171 and the rivet terminal 172 to prevent electrical contact between the battery can 171 and the rivet terminal 172, which are different in polarity from each other. Thus, the top surface of the battery can 171 having a substantially flat shape may serve as the positive electrode terminal of the battery 170.
The second gasket 173 includes a gasket exposure portion 173a and a gasket insertion portion 173b. The spacer exposing portion 173a is interposed between the terminal exposing portion 172a of the rivet terminal 172 and the battery can 171. The gasket insertion portion 173b is inserted between the terminal insertion portion 172b of the rivet terminal 172 and the battery can 171. At the time of caulking the terminal insertion part 172b, the gasket insertion part 173b may be deformed together and closely contact with the inner surface of the battery can 171. The second gasket 173 may be made of, for example, a polymer resin having an insulating property.
The pad exposing portion 173a of the second pad 173 may have a shape extending to cover the outer circumferential surface of the terminal exposing portion 172a of the rivet terminal 172. When the second gasket 173 covers the outer circumferential surface of the rivet terminal 172, it is possible to prevent a short circuit from occurring during the coupling of the electrical connection member such as a bus bar to the top surface of the battery can 171 and/or the rivet terminal 172. Although not shown, the pad exposing portion 173a may have a shape extending to cover a portion of the top surface of the terminal exposing portion 172a and the outer circumferential surface thereof.
When the second gasket 173 is made of a polymer resin, the second gasket 173 may be coupled with the battery can 171 and the rivet terminal 172 by thermal welding. In this case, the air tightness at the bonding interface between the second gasket 173 and the rivet terminal 172 and the bonding interface between the second gasket 173 and the battery can 171 can be enhanced. On the other hand, when the pad exposing portion 173a of the second pad 173 has a shape extending to the top surface of the terminal exposing portion 172a, the rivet terminal 172 may be integrally combined with the second pad 173 by insert injection molding.
The remaining area 175 corresponds to a negative terminal having a polarity opposite to that of the rivet terminal 172 except for an area occupied by the rivet terminal 172 and the second gasket 173 on the top surface of the battery can 171.
The second current collecting plate 176 is coupled to a lower portion of the electrode assembly 141. The second current collecting plate 176 is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the uncoated portion 146b of the negative electrode plate.
Preferably, the second current collecting plate 176 is electrically connected to the battery can 171. For this, at least a portion of the edge portion of the second current collecting plate 176 may be inserted and fixed between the inner surface of the battery can 171 and the first gasket 178 b. In one example, at least a portion of the edge portion of the second current collecting plate 176 may be fixed to a beading portion 180 formed at the lower end of the battery can 171 while being supported by the lower end surface of the beading portion 180 by welding. In a modification, at least a part of the edge portion of the second current collecting plate 176 may be directly welded to the inner wall surface of the battery can 171.
The second current collecting plate 176 may include a plurality of irregularities radially formed on a surface facing the uncoated portion 146 b. When the irregularities are formed, the irregularities may be press-fitted into the uncoated portion 146b by pressing the second current collecting plate 176.
Preferably, the second current collecting plate 176 and the end of the uncoated portion 146b may be coupled by welding (e.g., laser welding).
A sealing body 178 for sealing a lower open end (a second end having a second opening) of the battery can 171 includes a cap plate 178a and a first gasket 178b. The first gasket 178b electrically separates the cap plate 178a and the battery can 171. The crimp 181 fixes the edge of the cap plate 178a together with the first washer 178b. A vent portion 179 is provided in the cover plate 178 a. The ventilation portion 179 has substantially the same configuration as the above embodiment.
Preferably, the cap plate 178a may be made of a conductive metal material. However, since the first gasket 178b is interposed between the cap plate 178a and the battery can 171, the cap plate 178a has no electric polarity. The sealing body 178 serves to seal the lower open end of the battery can 171 and to discharge gas when the internal pressure of the battery cell 170 rises above a threshold value.
Preferably, the rivet terminal 172 electrically connected to the uncoated portion 146a of the positive electrode plate is used as a positive electrode terminal. And, a portion 175 of the top surface of the battery can 171, which is electrically connected to the uncoated portion 146b of the negative electrode plate through the second current collecting plate 176, except for the rivet terminal 172, is used as a negative electrode terminal. As described above, when two electrode terminals are located at the upper portion of the cylindrical battery, an electrical connection member such as a bus bar may be provided at only one side of the battery 170. This can simplify the structure of the battery pack and improve the energy density. Further, the portion 175 serving as the negative electrode terminal has a substantially flat shape, so that a sufficient bonding area can be ensured when the electrical connection members such as the bus bars are bonded. Therefore, in the battery 170, the resistance of the bonding site of the electrical connection member can be reduced to a preferable level.
When the lithium secondary battery is formed in the above-described electrode tab structure, the current concentration becomes smaller as compared with the battery having the electrode tab in the related art, and thus heat generation inside the battery can be effectively reduced. Therefore, the thermal stability of the battery can be improved.
The lithium secondary battery of the present invention as described above can be used to manufacture a battery pack. Fig. 8 schematically shows the structure of a battery pack according to an embodiment of the present invention. Referring to fig. 8, a battery pack 3 according to an embodiment of the present invention includes: a component that electrically connects the secondary batteries 1; and a pack case 2 accommodating the same. The secondary battery 1 is the battery cell of the above embodiment. In the figure, for convenience of explanation, components such as bus bars, cooling units, and external terminals for electrically connecting the secondary batteries 1 are omitted.
The battery pack 3 may be mounted to an automobile. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. Automobiles include four-wheeled vehicles or two-wheeled vehicles.
Fig. 9 is a view for explaining an automobile including the battery pack 3 of fig. 8.
Referring to fig. 9, an automobile 5 of an embodiment of the present invention includes a battery pack 3 of an embodiment of the present invention and operates by receiving electric power from the battery pack 3.
Hereinafter, the present invention will be described in more detail with reference to specific embodiments.
Example 1
The positive electrode active material Li [ Ni 0.9Co0.06Mn0.03Al0.01]O2, carbon nanotubes and PVDF binder having a single-peak particle size distribution and single particles with an average particle size D 50 of 3 μm were mixed in N-methylpyrrolidone in a weight ratio of 97.8:0.6:1.6. As a result, a positive electrode slurry was produced. The positive electrode slurry was coated on one surface of an aluminum current collector sheet, dried at 120 ℃, and then rolled. As a result, a positive electrode plate was manufactured.
The negative electrode active material (graphite: sio=95:5 weight ratio mixture), conductive material (super C), styrene Butadiene Rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5. As a result, a negative electrode slurry was produced. The negative electrode slurry was coated on one side of a copper current collector sheet, dried at 150 ℃, and then rolled. As a result, a negative electrode plate was manufactured.
The separator is interposed between the positive and negative electrode plates manufactured as described above, and then the separator/positive electrode plate/separator/negative electrode plate are sequentially stacked and then wound. As a result, an electrode assembly having a jelly-roll shape was manufactured. The electrode assembly manufactured as described above was inserted into a cylindrical battery can, and then an electrolyte was injected therein. As a result, 4680 batteries were manufactured.
Comparative example 1
A 4680 battery was produced by the same method as in example 1, except that Li [ Ni 0.9Co0.05Mn0.04Al0.01]O2 ] having a bimodal particle size distribution in which the secondary particles and large particles have an average particle diameter D 50 of 9 μm and the small particles have an average particle diameter D 50 of 4 μm was used as a positive electrode active material.
Experimental example
Hot box tests were performed on the 4680 batteries manufactured in example 1 and comparative example 1.
Specifically, a hot box evaluation was performed in which 4680 batteries manufactured in example 1 and comparative example 1 were placed in a hot box room at room temperature, heated to 130 ℃ at a heating rate of 5 ℃/min, and then held for 30 minutes. In addition, the change in battery temperature with time was measured. For accurate evaluation, the battery of example 1 was subjected to two hot box evaluations. Fig. 4 and 5 show the measurement results.
Fig. 5 is a graph showing the hot box test results of the 4680 battery manufactured in example 1, and fig. 6 is a graph showing the hot box test results of the 4680 battery manufactured in comparative example 1.
From fig. 5 and 6, it was confirmed that, for the lithium secondary battery of example 1 using the single-particle positive electrode active material, the voltage and temperature of the battery were stably maintained until 65 minutes passed. However, with the lithium secondary battery of comparative example 1, the battery temperature rapidly increased after 35 minutes.
Claims (18)
1. A lithium secondary battery, comprising:
An electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction;
a battery can accommodating the electrode assembly; and
A sealing body sealing the open end of the battery can,
Wherein the positive electrode plate comprises a positive electrode active material layer, and
Wherein the positive electrode active material layer contains 95 to 100 wt% of a positive electrode active material composed of single particles, quasi-single particles, or a combination thereof, based on the total weight of the positive electrode active materials present in the positive electrode active material layer, and
The average particle diameter D 50 of the positive electrode active material is below 5 mu m.
2. The lithium secondary battery of claim 1, wherein the positive electrode active material consists of single particles, quasi-single particles, or a combination thereof.
3. The lithium secondary battery according to claim 1, wherein the positive electrode active material layer contains a positive electrode active material having a unimodal particle size distribution that exhibits a unimodal in a volume cumulative particle size distribution map.
4. The lithium secondary battery according to claim 1, wherein the positive electrode active material contains a lithium-containing nickel oxide containing 80mol% or more of Ni based on the total mole number of transition metals.
5. The lithium secondary battery according to claim 1, wherein the positive electrode active material comprises a lithium-containing nickel oxide represented by the following chemical formula 1,
Li aNibCocM1 dM2 eO2 [ chemical formula 1]
Wherein in chemical formula 1, M 1 is at least one selected from the group consisting of Mn and Al, M 2 is at least one selected from the group consisting of Zr, W, ti, mg, ca, sr and Ba, 0.8.ltoreq.a.ltoreq. 1.2,0.83.ltoreq.b <1,0< c <0.17,0< d <0.17, 0.ltoreq.e.ltoreq.0.1.
6. The lithium secondary battery according to claim 1, wherein the primary particle diameter of the positive electrode active material is 0.5 μm to 5 μm.
7. The lithium secondary battery according to claim 1, wherein the negative electrode plate comprises a silicon-containing negative electrode active material.
8. The lithium secondary battery according to claim 1, wherein the negative electrode plate comprises a silicon-containing negative electrode active material and a carbon-containing negative electrode active material.
9. The lithium secondary battery of claim 8, wherein the silicon-containing anode active material and the carbon-containing anode active material are present in a weight ratio of 1:99 to 20:80.
10. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a cylindrical battery having a shape factor ratio of 0.4 or more.
11. The lithium secondary battery of claim 10, wherein the cylindrical battery is 46110 battery, 4875 battery, 48110 battery, 4880 battery, or 4680 battery.
12. The lithium secondary battery according to claim 1, wherein the positive electrode plate and the negative electrode plate each include an uncoated portion where no active material layer is formed,
Wherein the lithium secondary battery is a battery having a structure in which at least a portion of the uncoated portion of the positive electrode plate or the negative electrode plate defines an electrode tab.
13. The lithium secondary battery according to claim 12, wherein the positive electrode plate uncoated portion and the negative electrode plate uncoated portion are formed at one end portion of the positive electrode plate and one end portion of the negative electrode plate, respectively, in a direction in which the electrode assembly is wound,
Wherein a collector plate is bonded to the uncoated portion of the positive electrode plate and the uncoated portion of the negative electrode plate, respectively, and
The collector plate is connected to the electrode terminal.
14. The lithium secondary battery according to claim 13, wherein the positive plate uncoated portion and the negative plate uncoated portion are each processed into a plurality of segment forms capable of being independently bent, and
At least a portion of the plurality of segments is bent toward a winding center of the electrode assembly.
15. The lithium secondary battery according to claim 14, wherein at least a portion of the plurality of curved sections overlap with upper and lower ends of the electrode assembly, and
The collector plate is coupled with the plurality of overlapping sections.
16. The lithium secondary battery according to claim 13, wherein an insulating layer is further provided on the positive electrode plate, the insulating layer covering a portion of the positive electrode active material layer and a portion of the uncoated portion in a direction parallel to a winding direction.
17. A battery pack comprising the lithium secondary battery of any one of claims 1 to 16.
18. An automobile comprising the battery pack of claim 17.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR10-2021-0136709 | 2021-10-14 | ||
| KR10-2022-0049184 | 2022-04-20 | ||
| KR1020220121173A KR102673253B1 (en) | 2021-10-14 | 2022-09-23 | Lithium secondary battery |
| KR10-2022-0121173 | 2022-09-23 | ||
| PCT/KR2022/015624 WO2023063785A1 (en) | 2021-10-14 | 2022-10-14 | Lithium secondary battery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN118020194A true CN118020194A (en) | 2024-05-10 |
Family
ID=90943522
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202280065721.3A Pending CN118020194A (en) | 2021-10-14 | 2022-10-14 | Lithium secondary battery |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN118020194A (en) |
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2022
- 2022-10-14 CN CN202280065721.3A patent/CN118020194A/en active Pending
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