CN116705987B - Negative plate, electrochemical device and preparation method of electrochemical device - Google Patents
Negative plate, electrochemical device and preparation method of electrochemical device Download PDFInfo
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- CN116705987B CN116705987B CN202310973622.1A CN202310973622A CN116705987B CN 116705987 B CN116705987 B CN 116705987B CN 202310973622 A CN202310973622 A CN 202310973622A CN 116705987 B CN116705987 B CN 116705987B
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- 229910052744 lithium Inorganic materials 0.000 claims abstract description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 15
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- 229910052814 silicon oxide Inorganic materials 0.000 claims description 10
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- 239000003273 ketjen black Substances 0.000 claims description 4
- 239000007774 positive electrode material Substances 0.000 claims description 4
- OTYYBJNSLLBAGE-UHFFFAOYSA-N CN1C(CCC1)=O.[N] Chemical compound CN1C(CCC1)=O.[N] OTYYBJNSLLBAGE-UHFFFAOYSA-N 0.000 claims description 3
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 3
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 11
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- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 2
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 2
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- NDPGDHBNXZOBJS-UHFFFAOYSA-N aluminum lithium cobalt(2+) nickel(2+) oxygen(2-) Chemical compound [Li+].[O--].[O--].[O--].[O--].[Al+3].[Co++].[Ni++] NDPGDHBNXZOBJS-UHFFFAOYSA-N 0.000 description 1
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- 229910002102 lithium manganese oxide Inorganic materials 0.000 description 1
- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 description 1
- URIIGZKXFBNRAU-UHFFFAOYSA-N lithium;oxonickel Chemical compound [Li].[Ni]=O URIIGZKXFBNRAU-UHFFFAOYSA-N 0.000 description 1
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- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The embodiment of the invention relates to the technical field of secondary batteries, in particular to a negative plate, an electrochemical device and a preparation method thereof, wherein the negative plate comprises a negative current collector; the active coating is arranged on the negative electrode current collector and comprises an active material, a binder, a conductive agent and a semiconductor material, wherein the semiconductor material is provided with a plurality of holes. Through the mode, the semiconductor material provided with the holes is high in internal resistance in a low-temperature environment, and the conductivity of the negative electrode plate can be weakened, so that the migration of electrons in the negative electrode plate is delayed, the migration of lithium ions to the negative electrode can be facilitated, and the phenomenon that the negative electrode potential is excessively negative to cause lithium precipitation due to the overlarge electron density on the surface of the negative electrode plate is reduced.
Description
Technical Field
The embodiment of the invention relates to the technical field of secondary batteries, in particular to a negative plate, an electrochemical device and a preparation method thereof.
Background
Lithium batteries are widely used in the fields of mobile devices, electric vehicles, energy storage systems, and the like, in which lithium ions are transported between positive and negative electrodes to store and release electric energy. The lithium battery comprises a shell, a positive plate and a negative plate which are contained in the shell, a diaphragm and electrolyte, wherein the diaphragm is positioned between the positive plate and the negative plate, the electrolyte is arranged in the shell, the positive plate and the negative plate are immersed in the electrolyte, and the electrolyte provides an environment for chemical reaction of the positive plate and the negative plate.
However, in implementing embodiments of the present invention, the inventors found that: in the charging process of a low-temperature environment (10-40 ℃), the viscosity of electrolyte is continuously increased due to low temperature, lithium ions migrate from the positive electrode to the negative electrode to prevent the lithium ions from increasing, electrons on the surface of the negative electrode cannot react in time, the potential on the surface of the negative electrode is over-negative, the lithium ions are separated out on the surface of the negative electrode plate, the polarization degree of a lithium battery is serious, the capacity of the secondary battery is easily attenuated due to the polarization of the positive electrode and the negative electrode, and potential safety hazards exist.
Disclosure of Invention
The embodiment of the invention provides a negative plate, an electrochemical device and a preparation method thereof, which can reduce the phenomenon of lithium precipitation of the negative plate in a low-temperature environment.
In order to solve the technical problems, the invention adopts a technical scheme that: providing a negative electrode sheet comprising a negative electrode current collector; the active coating is arranged on the negative electrode current collector and comprises an active material, a binder, a conductive agent and a semiconductor material, wherein the semiconductor material is provided with a plurality of holes.
Optionally, the reactive coating satisfies at least one of the following conditions: (1) The mass percentage of the active material is 90.0% -98.5%; (2) the mass percentage of the binder is 1.0% -5.0%; (3) the mass percentage of the conductive agent is 0% -5.0%; (4) The mass percentage of the semiconductor material is 0.5% -9.0%.
Optionally, the active material comprises at least one of graphite, hard carbon, soft carbon, silicon oxide, silicon, or silicon oxide.
Optionally, the binder comprises at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, acrylonitrile copolymer, polyacrylic acid, and polyvinyl alcohol.
Optionally, the conductive agent includes at least one of conductive carbon black, carbon nanotube, graphene, carbon fiber, acetylene black, ketjen black.
Optionally, the semiconductor material comprises Bi 2 Te 3 、Bi 2 Se 3 、Bi 2 S 3 、As 2 Te 3 、ZrO 2 、CuO、ZnO、Sc 2 O 3 、TiO 2 、V 2 O 5 At least one of them.
Optionally, the semiconductor material has a particle size D 50 Is 10-3000 nanometers.
In order to solve the technical problems, the invention adopts a technical scheme that: another electrochemical device is provided, including a negative plate, a separator, and a positive plate, wherein the negative plate, the separator, and the positive plate are stacked in sequence, the polarities of the negative plate and the positive plate are opposite, and the negative plate is the negative plate described above. In order to solve the technical problems, the invention adopts a further technical scheme that: provided is a method of manufacturing a negative electrode sheet, including: providing an active material, a binder, a conductive agent, and a semiconductor material; placing the active material, binder, conductive agent and semiconductor material into a container; adding deionized water into the container, and uniformly stirring to obtain slurry; providing a negative electrode current collector; coating the slurry on the negative electrode current collector; and forming an active coating on the solid part of the slurry to obtain the negative plate.
The beneficial effects of the embodiment of the application are that: the negative electrode plate comprises a negative electrode current collector and an active coating arranged on the negative electrode current collector, the active coating comprises a semiconductor material provided with a plurality of holes, the internal resistance of the semiconductor material provided with the holes can be increased in a low-temperature environment, the conductivity of the negative electrode plate is weakened, the migration of electrons from the negative electrode current collector to the surface of the active coating is effectively delayed, the migration of lithium ions from the positive electrode plate to the negative electrode plate is facilitated, the risk of lithium precipitation caused by the overdischarge of the surface electron density of the negative electrode plate is reduced, and the service life of the battery is prolonged.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a negative plate according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a semiconductor material of a negative plate according to an embodiment of the present invention;
fig. 3 is a schematic view of a winding structure of a battery cell of an electrochemical device according to an embodiment of the present invention;
fig. 4 is a schematic structural view of an electrochemical device according to an embodiment of the present invention;
fig. 5 is a schematic diagram illustrating stacking of cells of an electrochemical device according to an embodiment of the present invention.
Reference numerals:
100. an electrochemical device; 20. a positive electrode tab; 30. a negative electrode ear; 11. a positive plate; 12. a diaphragm; 13. a negative electrode sheet; 14. a housing; 50. a hole; 131. a negative electrode current collector; 132. and (3) an active coating.
Detailed Description
As used herein, unless otherwise indicated, "a," "an," "the," "at least one," and "one or more" are used interchangeably without the use of quantitative terms. The use of the singular forms herein is intended to include the plural forms as well, unless the context clearly indicates otherwise.
In the description herein, it is to be noted that "above" and "below" do not include the present number, and "one or more" means two or more "in the meaning of" multiple "unless otherwise specified.
Where a composition is described as comprising or including a particular component, it is contemplated that optional components not referred to herein are not excluded from the composition, and that the composition may consist or consist of the recited components, or where a method is described as comprising or including a particular process step, it is contemplated that optional process steps not referred to herein are not excluded from the method, and that the method may consist or consist of the recited process steps.
For simplicity, only a few numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each point or individual value between the endpoints of the range is included within the range, although not explicitly recited. Thus, each point or individual value may be combined as a lower or upper limit on itself with any other point or individual value or with other lower or upper limit to form a range that is not explicitly recited.
Referring to fig. 1, the negative electrode sheet 13 includes a negative electrode current collector 131 and an active coating 132, the active coating 132 is disposed on the negative electrode current collector 131, the active coating 132 includes an active material, a binder, a conductive agent, and a semiconductor material, and the semiconductor material is provided with a plurality of holes 50. The plurality of holes 50 formed in the semiconductor material can increase internal resistance of the semiconductor material in a low-temperature environment (10-40 ℃), weaken conductivity of the negative electrode plate, effectively delay migration of electrons from the negative electrode current collector 131 to the surface of the active coating 132, facilitate migration of lithium ions from the positive electrode plate to the negative electrode plate, reduce risk of lithium precipitation caused by overdrawing of negative electrode potential due to overlarge electron density on the surface of the negative electrode plate, and prolong service life of the battery.
Wherein the inner diameter of the hole 50 is nano-sized, for example: the inner diameter of the holes 50 is 5 nm, 1 nm, etc. When the inner diameter of the hole 50 is also different according to the size of the semiconductor material, the required internal resistance is different, for example, the internal resistance is adjusted to different levels: adjusted to 1 micron, etc.
The holes 50 are uniformly distributed in the semiconductor material, and the semiconductor material may be uniformly distributed in the active coating 132, so that the internal resistance variation of each region of the active coating 132 is uniform. While the shape of the holes 50 may be cylindrical, inverted triangular, or other irregular shapes.
In some embodiments, the active material comprises 90.0-98.5% by weight, the binder comprises 1.0-5.0% by weight, the conductive agent comprises 0-5.0% by weight, the semiconductor material comprises 0.5-9.0% by weight, and the active material comprises the components according to the proportion, so that the negative plate has good conductivity and high stability, and the negative plate has good performance. Preferably, the mass percent of the semiconductor material is 1.0% -2.5%, and the effect of the mass percent of the semiconductor material is better in the range.
In some embodiments, the active material comprises at least any one of the group consisting of graphite, hard carbon, soft carbon, silicon oxide, silicon, and silicon oxide in one or more combinations. The graphite, the hard carbon, the soft carbon, the silicon oxide, the silicon or the silicon oxide has good conductivity, so that the graphite, the hard carbon, the soft carbon, the silicon oxide, the silicon or the silicon oxide is selected as the material of the active material, and the conductivity of the active material is ensured.
In some embodiments, the binder includes at least any one of the group consisting of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, acrylonitrile-based multipolymer, polyacrylic acid, polyvinyl alcohol, materials in which hydrogen is replaced with Li, na, ca, or the like, and combinations thereof. The viscosity of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, acrylonitrile multipolymer, polyacrylic acid and polyvinyl alcohol is high, and the carboxymethyl cellulose, the styrene-butadiene rubber, the polyvinylidene fluoride, the acrylonitrile multipolymer, the polyacrylic acid and the polyvinyl alcohol are selected as the adhesive, so that the viscosity of the adhesive can be improved, and the active material, the conductive agent and the semiconductor material can be combined more firmly.
In some embodiments, the conductive agent comprises at least any one of the group consisting of one or more combinations of conductive carbon black, carbon nanotubes, graphene, carbon fibers, acetylene black, ketjen black.
In some embodiments, the semiconductor material includes Bi 2 Te 3 、Bi 2 Se 3 、Bi 2 S 3 、As 2 Te 3 、ZrO 2 、CuO、ZnO、Sc 2 O 3 、TiO 2 、V 2 O 5 At least one of the group consisting of one or more combinations of (a) and (b). Preferably, the semiconductor material ZrO 2 、Sc 2 O 3 、Bi 2 Te 3 At least one of the group consisting of one or more combinations of the above. Bi in low temperature environment 2 Te 3 、Bi 2 Se 3 、Bi 2 S 3 、As 2 Te 3 、ZrO 2 、CuO、ZnO、Sc 2 O 3 、TiO 2 、V 2 O 5 As the semiconductor material, it is understood that the semiconductor material has poor electron conductivity and poor thermal conductivity, and that the semiconductor material does not have a significant increase or decrease in electrical conductivity with a change in temperature when the semiconductor material is placed in a low-temperature environment.
In some embodiments, the semiconductor material has a particle size D 50 Is 10-3000 nanometers. When the particle size is smaller than 10 nanometers, the semiconductor material is agglomerated in the dispersing process, the dispersing difficulty of slurry is increased, and when the particle size of the semiconductor material is larger than 3000 nanometers, the compaction density of the negative electrode plate 13 is reduced, so that the practical requirement cannot be met. Preferably, the semiconductor material D 50 20-200 nm.
In the embodiment of the invention, the anode plate comprises the anode current collector 131 and the active coating 132 arranged on the anode current collector 131, the active coating 132 comprises the semiconductor material provided with the holes 50, the internal resistance of the semiconductor material provided with the holes 50 can be increased in a low-temperature environment, the conductivity of the anode plate is weakened, the migration of electrons from the anode current collector 131 to the surface of the active coating 132 is effectively delayed, the migration of lithium ions from the anode plate to the anode plate is facilitated, the risk of lithium precipitation caused by the overdischarge of the anode potential due to the overlarge electron density on the surface of the anode plate is reduced, and the service life of the battery is prolonged. Specifically, part of the electrolyte is kept in the holes 50 of the semiconductor material, so that lithium ions can be conducted to the negative electrode through the liquid phase after being conducted from the center of the solid phase particles through the solid phase, and the migration of the lithium ions from the positive electrode to the negative electrode is accelerated.
An embodiment of the present invention provides an electrochemical device 100, as shown in fig. 3 and 4, the electrochemical device 100 including a case 14, an electrolyte, a negative electrode sheet 13, a separator 12, and a positive electrode sheet 11. The separator 12 is located between the negative electrode sheet 13 and the positive electrode sheet 11. The negative electrode sheet 13, the separator 12 and the positive electrode sheet 11 are wound to form a wound cell. Of course, in some embodiments, the number of the negative electrode sheets 13, the separator 12 and the positive electrode sheets 11 is multiple, that is, the negative electrode sheets 13 and the positive electrode sheets 11 are stacked alternately, and the separator 12 is arranged between any adjacent negative electrode sheets 13 and positive electrode sheets 11, so as to form a stacked cell, as shown in fig. 5.
The positive electrode sheet 11 includes a positive electrode current collector and a positive electrode coating layer disposed on the positive electrode current collector, the positive electrode coating layer including a positive electrode active material, a positive electrode adhesive, and a positive electrode conductive agent.
The positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, olivine structured lithium-containing phosphate, for example: liCoO 2 (lithium cobalt oxide), liNiO 2 Or LiMn 2 O 4 。
The positive electrode binder comprises at least one of styrene-butadiene rubber, water-based acrylic resin, carboxymethyl cellulose, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, hydrogenated nitrile, polytetrafluoroethylene, ethylene-vinyl acetate copolymer, polyvinyl alcohol and polyvinyl butyral.
The positive electrode conductive agent comprises at least one of graphite, superconducting carbon, acetylene black, conductive carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
In some embodiments, the mass percentage of the positive electrode active material is 95.0% -98.2%, the mass percentage of the positive electrode adhesive is 1.0% -5.0%, and the mass percentage of the positive electrode conductive agent is 0.3% -5.0%, so that the positive electrode plate has good conductivity and high stability according to the proportion.
The barrier film may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. In particular polyethylene, which can improve the safety of the electrochemical device through a shutdown effect.
The stacked cells formed by stacking or the wound cells formed by winding are arranged in the shell 14, electrolyte is injected into the shell 14, the stacked cells or the wound cells are soaked in the electrolyte, and the electrolyte is used for forming the stacked cells or the wound cells.
In order to facilitate the electrical connection between the electrochemical device 100 and the outside, the electrochemical device 100 further includes a positive electrode tab and a negative electrode tab, wherein one end of the positive electrode tab is connected to the positive electrode tab, the other end of the positive electrode tab extends out of the housing 14 through the housing 14, one end of the negative electrode tab is connected to the negative electrode tab, and the other end of the negative electrode tab extends out of the housing 14 through the housing 14. The other end of the positive electrode lug and the other end of the negative electrode lug are used for being electrically connected with external electronic equipment.
It should be noted that: the structure and function of the negative electrode sheet 13 of the electrochemical device 100 are the same as those of the negative electrode of the above embodiment, and the specific structure and function of the negative electrode sheet 13 will not be described here.
In order to better understand the effect of the negative electrode sheet 13 of the present invention, the inventors of the present application particularly conducted experimental comparisons as follows:
comparative example:
1) Preparing a positive plate: adding 97.5 percent of lithium cobaltate, 1.4 percent of conductive carbon black and 1.1 percent of polyvinylidene fluoride into 1.1 percent of nitrogen methyl pyrrolidone (nanometer P) according to the mass ratio, uniformly mixing to prepare positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector, welding a positive electrode lug, only carrying out single-layer coating, and coating the single-side surface density of 150.0g/m 2 A compacted density of 4.20g/cm 3 Then the strips are separated.
2) Preparation of the separator: porous polyethylene film is selected as the diaphragm.
3) Preparing a negative electrode sheet: graphite, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber are added into deionized water according to the mass ratio of 97.6 percent to 0.5 percent to 0.9 percent to 1.0 percent, and uniformly mixed to prepare negative electrode slurry, the negative electrode slurry is coated on a negative electrode current collector 131, and a negative electrode plate is prepared by coating, slitting and welding negative electrode lugs. Wherein the compaction density is 1.75g/cm 3 。
4) Assembly of electrochemical device: winding or laminating according to the comparison mode of the positive plate, the diaphragm and the negative plate, and injecting carbonate-based electrolyte (solute is 1mol/L LiPF 6 ) The electrochemical device preparation process is completed through packaging, formation, capacity division and the like.
Example 1:
1) Positive electrode sheet 11 preparation:
adding 97.5 percent of lithium cobaltate, 1.4 percent of conductive carbon black and 1.1 percent of polyvinylidene fluoride into the mixture according to the mass ratioAdding into nitrogen methyl pyrrolidone (nanometer P), mixing to obtain positive electrode slurry, coating the positive electrode slurry on positive electrode current collector, welding positive electrode lug 20, coating with single layer, and coating with single-side surface density of 150.0g/m 2 A compacted density of 4.20g/cm 3 And then carrying out striping.
2) Preparation of the separator: porous polyethylene film is selected as the diaphragm.
3) Preparing a negative electrode sheet 13:
graphite, carboxymethyl cellulose, styrene butadiene rubber and ZrO with particle size of 100 nanometers 2 Adding 97.6 percent by mass and 0.6 percent by mass and 1.2 percent by mass into deionized water, uniformly mixing to prepare negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector 131, compacting, slitting, and welding a negative electrode lug 30 to prepare the negative electrode plate 13. Wherein the compaction density is 1.75g/cm 3 。
3) Assembly of electrochemical device: winding or laminating the positive electrode sheet 11, the separator 12 and the negative electrode sheet 13 in a comparative manner, and injecting a carbonate-based electrolyte (solute 1mol/L LiPF 6 ) The electrochemical device preparation process is completed through packaging, formation, capacity division and the like.
Example 2:
unlike example 1, a negative electrode sheet 13 was prepared: graphite material, carboxymethyl cellulose, styrene butadiene rubber and ScO with particle size of 100 nm 2 Adding 97.6 percent by mass and 0.6 percent by mass and 1.2 percent by mass into deionized water, uniformly mixing to prepare negative electrode slurry, and then preparing the negative electrode sheet 13 by coating, compacting, slitting and welding the negative electrode lug 30. Wherein the compaction density is 1.75g/cm 3 。
Example 3:
unlike example 1, a negative electrode sheet 13 was prepared: graphite material, carboxymethyl cellulose, styrene butadiene rubber and Bi with the grain diameter of 100 nanometers 2 S 3 Adding 97.6 percent by mass and 0.6 percent by mass and 1.2 percent by mass into deionized water, uniformly mixing to prepare negative electrode slurry, and then preparing the negative electrode sheet 13 by coating, compacting, slitting and welding the negative electrode lug 30. Wherein the compaction density is 1.75g/cm 3 。
Lithium precipitation test:
1) Circulation at 0 ℃): in the environment of (0+/-1) DEG C, 0.8C constant current and constant voltage charge is carried out until 4.48V,0.05C current is cut off, the mixture is left for 10min, and 0.5C discharge is carried out until 3.0V; cycling was performed 200 times.
2) Cycling at 45 ℃): in the environment of (45+/-1) DEG C, 1.5C is charged to 4.48V at constant current and constant voltage, 0.05C is cut off, the mixture is left for 10min, and 0.5C is discharged to 3.0V; cycling 400 times.
Specific parameters of comparative examples and examples 1 to 3 are shown in table 1 below:
from the results in table 1, it can be seen that:
the electrochemical devices of examples 1 to 3 have slightly improved 400T capacity retention at 45 ℃ and reduced energy density, indicating that the electrochemical devices of the present application maintain significant performance at low temperatures without affecting the high temperature discharge capability and without affecting the energy density of the electrochemical device.
In conclusion, the negative plate has very remarkable effect of resisting the analysis phenomenon triggered by the low-temperature environment.
In the embodiment of the invention, the holes 50 are formed in the semiconductor material of the active coating 132 of the negative electrode plate of the electrochemical device, so that the internal resistance of the negative electrode plate in a low-temperature environment can be increased, the conductivity of the negative electrode plate is weakened, the migration of electrons from the negative electrode current collector 131 to the surface of the active coating 132 is effectively delayed, the migration of lithium ions from the positive electrode plate to the negative electrode plate is facilitated, the risk of lithium precipitation caused by the overdischarge of the negative electrode potential due to the overlarge electron density on the surface of the negative electrode plate is reduced, and the service life of the electrochemical device is prolonged.
It should be noted that the description of the present invention and the accompanying drawings illustrate preferred embodiments of the present invention, but the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, which are not to be construed as additional limitations of the invention, but are provided for a more thorough understanding of the present invention. The above-described features are further combined with each other to form various embodiments not listed above, and are considered to be the scope of the present invention described in the specification; further, modifications and variations of the present invention may be apparent to those skilled in the art in light of the foregoing teachings, and all such modifications and variations are intended to be included within the scope of this invention as defined in the appended claims.
Claims (4)
1. The method for preparing the electrochemical device is characterized by comprising a negative plate, a diaphragm and a positive plate, wherein the negative plate, the diaphragm and the positive plate are sequentially overlapped, the negative plate comprises a negative current collector and an active coating, the active coating is arranged on the negative current collector, the active coating comprises an active material, a binder, a conductive agent and a semiconductor material, the semiconductor material is provided with a plurality of holes, and the particle size D of the semiconductor material is equal to that of the negative current collector 50 100 nanometers, and the semiconductor material comprises Bi 2 S 3 Or ZrO(s) 2 Wherein the polarities of the negative plate and the positive plate are opposite, and the inner diameter of the hole is 1 nanometer or 5 nanometers;
the preparation of the negative plate comprises the following steps: the active material, the binder, the conductive agent and the semiconductor material are added into deionized water according to the mass ratio of 90.0% -98.5%, 1.0% -5.0%, 0% -5.0%, 0.5% -9.0% and uniformly mixed to prepare negative electrode slurry, the negative electrode slurry is coated on the negative electrode current collector, and negative electrode plates are prepared by compacting, slitting and welding negative electrode lugs, wherein the compacted density is 1.75g/cm 3 ；
Preparation of the separator: selecting a porous polyethylene film as a diaphragm;
the positive plate is prepared by the following steps: adding 95.0-98.2% of positive active material, 1.0-5.0% of positive adhesive and 0.3-5.0% of positive conductive agent into azomethyl pyrrolidone according to the mass ratio, uniformly mixing to obtain positive slurry, coating the positive slurry on a positive current collector, compacting, welding positive lugs, and then stripping, wherein the single-sided surface density of the coating is 150.0g/m 2 A compacted density of 4.20g/cm 3 ；
Adding lithium cobaltate, conductive carbon black and polyvinylidene fluoride into nitrogen methyl pyrrolidone according to the mass ratio of 95.0-98.2 percent to 1.0-5.0 percent to 0.3-5.0 percent to prepare anode slurry;
assembly of the electrochemical device: according to the sequential overlapping and winding of the positive plate, the diaphragm and the negative plate to form a battery cell, injecting electrolyte, and forming the electrochemical device through encapsulation, formation and capacity division, wherein the electrochemical device is charged to 4.48V at a constant current and a constant voltage of 1.5C and is subjected to current cutoff of 0.05C in an environment of 45 ℃, and is placed for 10min, and 0.5C is discharged to 3.0V; the lithium is not separated out after 400 times of circulation, and the capacity retention rate reaches more than 86.8 percent.
2. The method of claim 1, wherein the step of determining the position of the substrate comprises,
the active material includes at least one of graphite, hard carbon, soft carbon, silicon oxide, silicon, or silicon oxide.
3. The method of claim 1, wherein the step of determining the position of the substrate comprises,
the binder comprises at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, acrylonitrile copolymer, polyacrylic acid and polyvinyl alcohol.
4. The method of claim 1, wherein the step of determining the position of the substrate comprises,
the conductive agent comprises at least one of carbon nano tube, graphene, carbon fiber, acetylene black and ketjen black.
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