CN100521293C - Non-aqueous electrolyte secondary battery pack - Google Patents

Non-aqueous electrolyte secondary battery pack Download PDF

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Publication number
CN100521293C
CN100521293C CNB2006100063311A CN200610006331A CN100521293C CN 100521293 C CN100521293 C CN 100521293C CN B2006100063311 A CNB2006100063311 A CN B2006100063311A CN 200610006331 A CN200610006331 A CN 200610006331A CN 100521293 C CN100521293 C CN 100521293C
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electrolyte secondary
nonaqueous electrolyte
secondary battery
battery pack
temperature
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CN1805172A (en
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永山雅敏
中岛琢也
村冈芳幸
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

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Abstract

A non-aqueous electrolyte rechargeable battery pack is provided, which includes a measuring unit for measuring a battery voltage and a battery temperature and a control unit for controlling charge and discharge based on a measuring result of the measuring unit. A plurality of cylindrical non-aqueous electrolyte rechargeable batteries each having positive and negative terminals at a cover and a bottom are accommodated in a battery housing in such a manner that side faces of adjacent non-aqueous electrolyte rechargeable batteries face each other. All the cylindrical non-aqueous electrolyte rechargeable batteries are electrically connected to one another. B/A is set to be in a range between 0.02 and 0.2 where A is a diameter of each cylindrical non-aqueous electrolyte rechargeable battery and B is a distance between the side faces of the adjacent batteries. Due to this, it is possible to realize the non-aqueous electrolyte rechargeable battery pack having a structure suitable for outdoor use as a power source for an electric tool.

Description

Non-aqueous electrolyte secondary battery pack
Technical Field
The present invention relates to a structure of a nonaqueous electrolyte secondary battery pack (battery pack), and more particularly, to an arrangement suitable for improving the characteristics of a plurality of batteries connected to each other.
Background
Since nonaqueous electrolyte secondary batteries, such as lithium ion secondary batteries, have a higher energy density than other secondary batteries, the market is expanding for power tool applications, such as power sources for electric power tools, in addition to consumer applications, such as power sources for portable devices.
Regardless of the battery system, the secondary battery for electric power tools is designed to have a simple cylindrical structure because it has an enlarged electrode area for improving output characteristics. In hybrid electric vehicles that are put into practical use prior to electric power tool use, it is common to connect the lid surface and the bottom surface of a cylindrical battery to form an elongated module, and then connect the module in series to the chassis of the vehicle so as to be arranged in the lateral direction and stacked in the lateral direction (for example, japanese unexamined patent application publication No. 2001-155789). In this structure, since joule heat generated from each battery is easily accumulated during high-rate charge and discharge, a certain gap is provided between each module to facilitate use of cooling air from the outside in order to improve heat dissipation of the battery pack.
In the case of a nonaqueous electrolyte secondary battery for a hybrid electric vehicle, if a large current can be instantaneously discharged at the time of starting and acceleration, then the vehicle can be driven by an internal combustion engine. However, in the case of a nonaqueous electrolyte secondary battery for an electric power tool, the driving source is only a battery, and when a structure for improving the heat dissipation of the battery pack is simply adopted, for example, under cold conditions, when the impedance of the battery reaction is large, it is difficult to continuously drive the electric power tool.
Disclosure of Invention
The present invention has been made in view of the above-described problems, and an object thereof is to provide a nonaqueous electrolyte secondary battery pack having a structure suitable for outdoor use as a power source for electric power tools.
In order to solve the above conventional problems, a nonaqueous electrolyte secondary battery pack of the present invention includes: a cylindrical nonaqueous electrolyte secondary battery having a lid surface and a bottom surface provided with positive and negative electrode terminals, a battery container for containing a plurality of the nonaqueous electrolyte secondary batteries, a measurement unit for measuring a battery voltage and a battery temperature, and a control unit for controlling charging and discharging based on a measurement result of the measurement unit; wherein all the cylindrical nonaqueous electrolyte secondary batteries are arranged in such a manner that side surfaces thereof face each other and are electrically connected in the battery container, and when the diameter of the cylindrical nonaqueous electrolyte secondary battery is defined as A and the distance between the side surfaces of the battery is defined as B, the B/A is in the range of 0.02 to 0.2.
The present inventors have conducted intensive studies and, as a result, have found that: as the structure of the battery pack, one having a moderate heat storage property is suitable for continuous high-rate discharge in a cold environment. Specifically, the side surfaces of the plurality of cells are opposed to each other while optimizing the distance therebetween, thereby exhibiting appropriate heat dissipation at high temperatures, and the joule heat generated during high-rate discharge is effectively utilized in cold environments to raise the temperature of the cells themselves, thereby enabling continuous discharge by reducing the impedance of the cell reaction.
Drawings
Fig. 1 is a schematic perspective view of a nonaqueous electrolyte secondary battery pack according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view taken along line II-II of FIG. 1.
FIG. 3 is a schematic sectional view taken along line III-III in FIG. 1.
Fig. 4 is a schematic sectional view taken along line IV-IV of fig. 1.
Fig. 5 is a view showing an example of the shape of a notch provided in the separator.
Detailed Description
The following description of the preferred embodiments of the present invention will be made with reference to the accompanying drawings.
Fig. 1 is a schematic perspective view of a nonaqueous electrolyte secondary battery pack of the present invention, fig. 2 is a sectional view taken along line II-II in fig. 1, fig. 3 is a sectional view taken along line III-III in fig. 1, and fig. 4 is a sectional view taken along line IV-IV in fig. 1. The plurality of cylindrical nonaqueous electrolyte secondary batteries 1 are provided with positive and negative terminals (not shown) on the top and bottom surfaces thereof, and all the batteries are arranged in the battery container 2 so that the side surfaces thereof face each other and are electrically connected to each other. A measuring unit 3 for measuring the battery voltage and the battery temperature, and a control unit 4 for controlling charging and discharging based on the measurement result of the measuring unit are disposed adjacent to the cylindrical nonaqueous electrolyte secondary battery 1, thereby constituting a nonaqueous electrolyte secondary battery pack 5 of the present invention.
Here, all the cylindrical nonaqueous electrolyte secondary batteries 1 in the nonaqueous electrolyte secondary battery pack 5 must be arranged so that the side surfaces thereof face each other. Even in the case where a thin and long module such as that of patent document 1 is configured by connecting the top surface and the bottom surface of the cylindrical nonaqueous electrolyte secondary battery 1, although appropriate heat dissipation properties can be exhibited at high temperatures, the heat dissipation properties are too high in a cold environment, and therefore, it is impossible to have appropriate heat storage properties that are the essence of the present invention.
In order to achieve both heat dissipation and heat storage, when the diameter of the cylindrical nonaqueous electrolyte secondary battery 1 is defined as "a" and the distance between the side surfaces of the battery is defined as "B", the B/a must be in the range of 0.02 to 0.2. When the B/a is 0.02 or less, the cells are too close to each other, and therefore, heat storage property is not critical, but heat radiation property under a high temperature environment is poor. On the contrary, when the B/a exceeds 0.2, the batteries are too separated, and therefore, the heat storage property in a cold environment is poor although the heat radiation property is not critical.
In order to set the B/a to the above-mentioned predetermined value, it is preferable to provide a separator 6 for separating adjacent side surfaces of the nonaqueous electrolyte secondary battery 1 in the battery container 2, in order to avoid a change in dimension (B/a value) due to vibration caused by use. In addition, it is preferable that the separator 6 has a through-hole 7 in order to make the generated joule heat uniform in the battery pack 5. In view of both the uniformity of the temperature and the strength of the separator 6, the area ratio of the through holes 7 in the separator 6 (hereinafter referred to as "void ratio") is preferably 10 to 70%. If the porosity is less than 10%, thermal convection due to the through-holes 7 is insufficient, and therefore the temperature uniformity in the battery pack 7 is reduced. On the contrary, when the porosity exceeds 70%, the temperature in the battery pack 5 tends to be uniform by the thermal convection, but the strength of the separator 6 is lowered, and it becomes difficult to secure the mechanical strength. Here, the through-hole 7 in the partition plate 6 may be an irregular notch 7, and the same effect can be obtained by using these in combination.
In the fully charged state, the voltage at which the nonaqueous electrolyte secondary batteries 1 of the present invention are connected in series is preferably 12.6 to 42V. The above-mentioned preferable range corresponds to 3 to 10 batteries, since the nonaqueous electrolyte secondary battery generally exhibits a closed circuit voltage of about 4.2V at the time of full charge, although it depends on the positive electrode active material. When the voltage is lower than 12.6V (2 or less cells) in the fully charged state, the heat storage property is lowered due to the shortage of joule heat, and the effect of the present invention is hardly exhibited. In addition, when the voltage exceeds 42V (the battery is 11 or more) in the fully charged state, the heat storage becomes excessive, and therefore, there is a problem that the heat radiation property at high temperature is lowered.
In the present invention, the control unit 4 preferably has a monitoring function of stopping the charge and discharge when the surface temperature of the cylindrical nonaqueous electrolyte secondary battery 1 detected by the measuring unit 3 is 60 to 80 ℃. When the temperature at which the charging and discharging are stopped is lower than 60 ℃, there is a problem that the charging and discharging are stopped even if the battery temperature slightly rises. On the other hand, if the temperature at which charging and discharging are stopped exceeds 80 ℃, if abnormal overheating occurs due to overcharge or the like, the timing of stopping energization is delayed, and thus there is a problem that the battery pack 5 itself is overheated.
As the negative electrode active material contained in the negative electrode material of the nonaqueous electrolyte secondary battery 1 to which the present invention is applied, a carbon material capable of lithium intercalation/deintercalation, a crystalline metal oxide, an amorphous metal oxide, and the like can be used. Examples of the carbon material include non-graphitizable carbon materials such as coke and glassy carbon, and graphites of highly crystalline carbon materials having a developed crystal structure, and specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, and the like), graphites, glassy carbons, organic polymer compound sintered bodies (materials carbonized by sintering a phenol resin, a furan resin, or the like at an appropriate temperature), carbon fibers, and activated carbon.
As the binder contained in the negative electrode, specifically, polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, and the like can be considered. Generally, a known binder used for the negative electrode mixture of such a battery can be used. In addition, a known additive or the like may be added to the negative electrode mixture as necessary.
The positive electrode active material of the nonaqueous electrolyte secondary battery 1 to which the present invention is applied may be any material as long as it is a conventionally known positive electrode material capable of intercalating and deintercalating lithium and containing a sufficient amount of lithium. Specifically, the general formula LiM is preferably usedxOy(wherein, 1)<x≦2,2<y ≦ 4, and M contains at least 1 or more of Co, Ni, Mn, Fe, Al, V, and Ti), a complex metal oxide composed of lithium and a transition metal, an intercalation compound containing lithium, or the like.
As the binder contained in the positive electrode, a known binder used for a positive electrode mixture of such a battery can be generally used. Specifically, polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, and the like can be considered. In addition, a known additive or the like may be added to the positive electrode mixture as necessary. Specifically, carbon black or the like may be added.
The nonaqueous electrolytic solution is obtained by dissolving an electrolyte in a nonaqueous solvent.
As the nonaqueous solvent, ethylene carbonate (hereinafter, referred to as EC) or the like having a relatively high dielectric constant and hardly decomposed by graphite constituting the negative electrode can be used as a main solvent. In particular, when a graphite material is used for the negative electrode, EC is preferably used as the main solvent, but a compound in which a halogen element is substituted for a hydrogen atom in EC may be used.
Further, by substituting a part of a material that reacts with graphite such as propylene carbonate (hereinafter referred to as PC) with the component 2 solvent, for EC as a main solvent, and a compound obtained by substituting a hydrogen atom in EC with a halogen element, further excellent characteristics can be obtained.
Examples of the solvent of the component 2 include propylene carbonate, butylene carbonate, vinylene carbonate, 1, 2-dimethoxyethane, diethoxymethane, γ -butyrolactone, valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, sulfolane, and methylsulfolane.
Further, it is preferable to use a low viscosity solvent in combination with a non-aqueous solvent to improve the current characteristics by increasing the conductivity and to improve the safety by reducing the reactivity with lithium metal.
Examples of the low-viscosity solvent include symmetrical or asymmetrical chain carbonates such as diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate, carboxylic acid esters such as methyl propionate and ethyl propionate, and phosphoric acid esters such as trimethyl phosphate and triethyl phosphate. These low-viscosity solvents may be used either singly or in combination of 2 or more.
The electrolyte is not particularly limited as long as it is a lithium salt that is dissolved in a nonaqueous solvent and exhibits ion conductivity, and for example, LiPF can be used6、LiClO4、LiAsF6、LiBF4、LiB(C6H5)4、LiCH3SO3、CF3SO3Li, LiCl, LiBr, and the like. As the electrolyte, LiPF is particularly preferably used6. These electrolytes may be used alone in 1 kind, or may be used in combination with 2 or more kinds.
The nonaqueous electrolyte secondary battery 1 of the present invention is not limited to the above-described lithium ion secondary battery, and similar effects can be obtained even in a battery system using a solid electrolyte and a gel electrolyte. The nonaqueous electrolyte secondary battery 1 of the present invention may be cylindrical in shape, and the diameter and length thereof are not limited.
As the material of the battery can, Fe, Ni, stainless steel, Al, Ti, or the like can be used. The battery can may be subjected to a treatment such as plating in order to prevent electrochemical corrosion by the nonaqueous electrolytic solution as the battery is charged and discharged.
(example 1)
(i) Production of positive electrode
For the preparation of positive electrode, LiCoO is used2Is a positive electrode active material. The positive electrode material can be obtained by mixing lithium carbonate (Li) as a raw material in a predetermined number of moles2CO3) And cobalt oxide (Co)3O4) And then sintered at 900 deg.c in an air atmosphere for 10 hours.
A paste-like positive electrode mixture was obtained by adding 3 parts by weight of acetylene black as a conductive material to 100 parts by weight of a positive electrode active material, preparing an N-methylpyrrolidone solution of polyvinylidene fluoride so as to contain 5 parts by weight of polyvinylidene fluoride as a binder, and stirring and mixing the mixture. Next, an aluminum foil having a thickness of 20 μm was used as a current collector, and the above paste-like positive electrode mixture was applied to both surfaces thereof, dried, rolled with a roll, cut into a predetermined size, and then used as a positive electrode.
(ii) Production of negative electrode
The negative electrode was produced as follows. First, 3 parts by weight of styrene-butadiene rubber as a binder was mixed with 100 parts by weight of flake graphite pulverized and classified to have an average particle size of about 20 μm, and then an aqueous solution of carboxymethyl cellulose was added to make the solid content 1 part by weight, followed by stirring and mixing to obtain a paste-like negative electrode mixture. A copper foil having a thickness of 15 μm was used as a current collector, and a paste-like negative electrode mixture was applied to both surfaces thereof, dried, rolled with a roll, cut into a predetermined size, and then used as a negative electrode.
(iii) Preparation of non-aqueous electrolyte
The nonaqueous electrolytic solution used was: at a speed of 30: 70 of LiPF is dissolved in a solvent prepared from EC and methyl ethyl carbonate6The resulting solution was 1.0 mol/l.
(iv) Production of nonaqueous electrolyte Secondary Battery
A cylindrical nonaqueous electrolyte secondary battery 1 having a diameter of 26mm and a height of 65mm was produced by using the above-mentioned positive electrode, negative electrode and nonaqueous electrolyte. The process steps are detailed below.
The positive and negative electrode strips were laminated with a separator made of a microporous polyethylene film interposed therebetween, and then wound in the longitudinal direction a plurality of times to produce a spiral electrode body. Next, an insulating plate was inserted into the bottom, and the electrode body was housed in an iron battery can with nickel plating applied on the inside. Then, one end of a negative electrode lead made of copper is pressure-welded to the negative electrode, and the other end is welded to the battery can, whereby the battery can becomes an external terminal of the negative electrode. On the other hand, one end of a positive electrode lead made of aluminum is attached to the positive electrode, and the other end is electrically connected to the battery cover by being separated by a current interrupting thin plate for interrupting current in accordance with the internal pressure of the battery, whereby the battery cover is an external terminal of the positive electrode.
After a nonaqueous electrolyte prepared by dissolving an electrolyte in a nonaqueous solvent is injected into the battery can, the battery can is caulked and sealed by a separator of an insulating sealing gasket coated with an oxidized pitch. Finally, the insulating tube mainly composed of polyethylene terephthalate was thermally shrunk to be integrated with the outer can, thereby producing a cylindrical nonaqueous electrolyte secondary battery 1.
(v) Production of nonaqueous electrolyte secondary battery pack
4 of the nonaqueous electrolyte secondary batteries 1 described above were connected in series in the lateral direction at an interval of 2.6mm in the inter-battery distance (B/a ═ 0.1). Here, a connection plate made of nickel was used for connection between the batteries without using a separator, and the connection was performed by resistance welding. In the centrally disposed nonaqueous electrolyte secondary battery, in order to measure the temperature during charging and discharging, a temperature monitoring measuring unit 3 (thermocouple) is closely attached to the insulating tube of the electrolyte secondary battery 1, and the temperature at which charging and discharging are stopped (hereinafter referred to as the monitored temperature) is set to 60 ℃. Finally, the positive and negative terminals of the nonaqueous electrolyte secondary battery 1 were connected, and the battery pack was covered with a case made of ABS (acrylonitrile-styrene-butadiene) resin, thereby producing a nonaqueous electrolyte secondary battery pack as shown in fig. 1. This was set as the nonaqueous electrolyte secondary battery pack of example 1.
Comparative example 1
A nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 1, except that 4 nonaqueous electrolyte secondary batteries 1 were connected in series in the vertical direction in the nonaqueous electrolyte secondary battery pack of example 1. This was set as the nonaqueous electrolyte secondary battery pack of comparative example 1.
(examples 2 to 3, comparative examples 2 to 3)
A nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 1 except that the distances between the nonaqueous electrolyte secondary batteries 1 in example 1 were set to 0.26mm (B/a equals 0.01), 0.52mm (B/a equals 0.02), 5.2mm (B/a equals 0.2), and 7.8mm (B/a equals 0.3), respectively. These were set as the nonaqueous electrolyte secondary battery packs of comparative examples 2, examples 2 to 3, and comparative example 3, respectively.
(vi-a) activated Charge-discharge
For each of the above nonaqueous electrolyte secondary battery packs, the charging voltage of each unit cell was controlled in an environment of 25 ℃, constant-current charging was performed at a charging current of 2A until the fastest one unit cell reached 4.2V, and then constant-voltage charging was performed until the charging current was reduced to 200 mA. After 20 minutes of rest, the discharge was carried out to 2.5V at a current value of 25A.
The following evaluations were performed on each nonaqueous electrolyte secondary battery pack after activation and charge/discharge.
(Low temperature discharge test)
After charging under the same conditions as the above-described activation charging and discharging, each nonaqueous electrolyte secondary battery pack was left to stand in an environment at 0 ℃ for 5 hours, and then discharged at a current value of 25A to 2.5V in an environment at 0 ℃. The discharge capacity thereof is shown in table 1.
(high temperature Charge test)
Charging was performed under the same conditions as the above-described activation charging and discharging except that the ambient temperature was set to 40 ℃, and the charging was stopped when the battery temperature reached the monitoring temperature. The charge capacity is shown in table 1.
(vibration stability test)
Each nonaqueous electrolyte secondary battery pack is vibrated at an oscillation frequency of 10 to 30Hz and an amplitude of 3mm for 30 minutes in an environment at 25 ℃. Vibration of the nonaqueous electrolyte secondary battery pack in the longitudinal direction and the lateral direction was repeated 3 times, respectively. The assembled battery was disassembled, and the change in the distance between the batteries before and after the vibration test was confirmed. The results are shown in Table 1, and the change observed with the naked eye is expressed as "large shift"; no change was observed with the naked eye but a change of 0.1mm or more was observed as measured with a vernier caliper, which was indicated as "small movement"; changes below 0.1mm are indicated as "no movement".
TABLE 1
Number of batteries Direction of arrangement B/A Partition board Pore shape void fraction Monitoring temperature (. degree.C.) Low temperature discharge capacity (Ah) High temperature charging capacity (Ah) Stability to vibration
Example 1 4 Transverse direction 0.1 Is not provided with Without holes 60 1.88 2.43 Big movement
Example 2 4 Transverse direction 0.02 Is not provided with Without holes 60 1.88 2.22 Big movement
Example 3 4 Transverse direction 0.2 Is not provided with Without holes 60 1.03 2.43 Big movement
Comparative example 1 4 Longitudinal direction 60 0.55 2.50 Big movement
Comparative example 2 4 Transverse direction 0.01 Is not provided with Without holes 60 1.88 2.05 Big movement
Comparative example 3 4 Transverse direction 0.3 Is not provided with Without holes 60 0.87 2.45 Big movement
It is understood from comparative example 1 that the low-temperature discharge capacity is greatly reduced due to the longitudinal arrangement of the nonaqueous electrolyte secondary batteries 1. Although this structure has high heat dissipation properties, it is considered that heat storage properties in a cold environment are poor, and this is a result. Similarly, in comparative example 3 in which the distance between cells was too large, the low-temperature discharge characteristics were degraded, although the distance between cells was not as large as in comparative example 1, even though the nonaqueous electrolyte secondary batteries 1 were arranged in the lateral direction.
In contrast to these comparative examples, each of the examples in which the nonaqueous electrolyte secondary batteries 1 were arranged in the lateral direction and the inter-battery distance was optimized exhibited excellent low-temperature discharge characteristics. However, if the distance between the cells is too short as in comparative example 2, the heat storage property becomes excessive, and the temperature reaches the monitored temperature quickly, so that the high-temperature charge capacity tends to decrease. From this, in order to achieve the effects of the present invention, when the cylindrical nonaqueous electrolyte secondary batteries 1 are arranged in the battery housing container in the lateral direction, and further the diameter a of the cylindrical nonaqueous electrolyte secondary batteries 1 and the distance between the battery side surfaces B are set, B/a must be in the range of 0.02 to 0.2, among others: when B/A is 0.1, a higher value of low-temperature discharge capacity and high-temperature charge capacity can be obtained.
(example 4)
In the above-described example, a nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 1 except that an ABS resin separator 6 was disposed so as to keep the distance between cells at 2.6mm (B/a ═ 0.1) in the nonaqueous electrolyte secondary battery pack of example 1, which could obtain good results. This was set as the nonaqueous electrolyte secondary battery pack of example 4.
(examples 5 to 9)
A nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 4, except that through-holes 7 were formed in a separator 6 so that the porosity thereof was 5, 10, 40, 70, and 80%. Each of these batteries was the nonaqueous electrolyte secondary battery pack of examples 5 to 9.
(example 10)
A nonaqueous electrolyte secondary battery pack of example 4 was produced in the same manner as in example 4, except that a notch was provided in the separator 6 so that the porosity thereof was 40%. This was set as the nonaqueous electrolyte secondary battery pack of example 10.
(examples 11 to 14)
A nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 7, except that 2, 3, 10, and 12 cells were arranged in series in the lateral direction in the nonaqueous electrolyte secondary battery pack of example 7. Each of these was set as the nonaqueous electrolyte secondary battery pack of examples 11 to 14.
(examples 15 to 18)
A nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 7, except that the temperature for stopping charge/discharge was set to 50, 70, 80, and 85 ℃. Each of these batteries was the nonaqueous electrolyte secondary battery pack of examples 15 to 18.
(vi-b) activated Charge-discharge
In the battery packs of examples 4 to 18, the charging voltage of each cell was controlled in an environment of 25 ℃, constant current charging was performed at a charging current of 2A until the fastest one cell reached 4.2V, and then constant voltage charging was performed until the charging current was reduced to 200 mA. After 20 minutes of rest, the discharge was carried out to 2.5V at a current value of 25A.
The following evaluations were performed on each nonaqueous electrolyte secondary battery pack after activation and charge/discharge.
(Low temperature discharge test)
After charging under the same conditions as the above-described activation charging and discharging, each nonaqueous electrolyte secondary battery pack was left to stand in an environment at 0 ℃ for 5 hours, and then discharged at a current value of 25A to 2.5V in an environment at 0 ℃. The discharge capacity thereof is shown in table 2.
(high temperature Charge test)
Charging was performed under the same conditions as the above-described activation charging and discharging except that the ambient temperature was set to 40 ℃, and the charging was stopped when the battery temperature reached the monitoring temperature. The charge capacity is shown in table 2.
(vibration stability test)
Each nonaqueous electrolyte secondary battery pack is vibrated at an oscillation frequency of 10 to 30Hz and an amplitude of 3mm for 30 minutes in an environment at 25 ℃. Vibration of the nonaqueous electrolyte secondary battery pack in the longitudinal direction and the lateral direction was repeated 3 times, respectively. Then, each nonaqueous electrolyte secondary battery pack was decomposed, and changes in the distance between the batteries before and after the vibration test were confirmed. The results are shown in Table 2, in which the change observed with the naked eye appears, and the result is expressed as "large movement"; no change was observed with the naked eye but a change of 0.1mm or more was observed as measured with a vernier caliper, which was indicated as "small movement"; changes below 0.1mm are indicated as "no movement".
(overcharge stability test)
The nonaqueous electrolyte secondary battery packs of examples 5 to 9 and 15 to 18 were subjected to a charging test of 8A in an environment of 25 ℃ and were stopped when the charge/discharge stop temperature set for each nonaqueous electrolyte secondary battery pack was reached. The maximum reached temperature after the stop displayed by the measurement unit 3 is shown in table 2.
TABLE 2
Number of batteries Arrangement of B/A Partition board Pore shape void fraction Monitoring temperature (. degree.C.) Low temperature discharge capacity (Ah) High temperature charging capacity (Ah) Stability to vibration Maximum arrival temperature
Example 4 4 Transverse direction 0.1 ABS Without holes 60 1.85 2.45 Without movement
Example 5 4 Transverse direction 0.1 ABS Pores 5% 60 1.90 2.44 Without movement 77
Practice ofExample 6 4 Transverse direction 0.1 ABS The hole is 10% 60 2.04 2.43 Without movement 70
Example 7 4 Transverse direction 0.1 ABS 40% of holes 60 2.05 2.40 Without movement 62
Example 8 4 Transverse direction 0.1 ABS 70% of holes 60 2.05 2.38 Mobile small 61
Example 9 4 Transverse direction 0.1 ABS 80% of holes 60 2.04 2.39 Big movement 62
Example 10 4 Transverse direction 0.1 ABS The gap is 40% 60 2.04 2.44 Without movement
Example 11 2 Transverse direction 0.1 ABS 40% of holes 60 1.07 2.52 Without movement
Example 12 3 Transverse direction 0.1 ABS 40% of holes 60 1.90 2.52 Without movement
Example 13 10 Transverse direction 0.1 ABS 40% of holes 60 2.05 2.44 Without movement
Example 14 12 Transverse direction 0.1 ABS 40% of holes 60 2.04 2.22 Without movement
Example 15 4 Transverse direction 0.1 ABS 40% of holes 50 2.05 2.23 Without movement 52
Example 16 4 Transverse direction 0.1 ABS 40% of holes 70 2.06 2.51 Without movement 73
Example 17 4 Transverse direction 0.1 ABS 40% of holes 80 2.04 2.52 Without movement 85
Example 18 4 Transverse direction 0.1 ABS 40% of holes 85 2.05 2.52 Without movement 97
With respect to the presence or absence of the separator 6, even in the case where the distance between the cells was the same, example 4 exhibited excellent vibration resistance as compared with example 1. Therefore, when vibration resistance is required for a device on which the nonaqueous electrolyte secondary battery pack of the present invention is mounted, it is preferable to provide a separator 6 for separating the adjacent side surfaces of the batteries in the battery storage container 2. Further, when the through-holes 7 as in examples 5 to 9 and the notches 7 (see fig. 5A) as in example 10 were provided in the separator 6, the low-temperature discharge characteristics were improved. This is considered to be because the through-hole 7 or the notch 7 is provided in the separator 6, so that the generated joule heat is easily equalized in the battery storage container 2. However, in example 5 having a porosity of 5%, the above-mentioned effects are not so large. In example 9 having a porosity of 80%, the mechanical strength was reduced, and the vibration resistance was not so high. As described above, it is preferable to provide the separator 6 between the cells, provide the through-hole 7 and/or the notch 7 in the separator 6, and set the porosity to 10 to 70%.
Regarding the number of batteries connected in series, in example 11 in which the number of nonaqueous electrolyte secondary batteries 1 was 2, the heat dissipation property became excessive, and the low-temperature discharge characteristic tended to be slightly lowered. On the other hand, in example 14 in which the number of nonaqueous electrolyte secondary batteries 1 was 12, the heat storage property became excessive, and the high-temperature charge capacity tended to be slightly decreased. Accordingly, in order to significantly improve the effect of the present invention, it is preferable to set the voltage at which the nonaqueous electrolyte secondary blown batteries 1 are connected in series to 12.6 to 42V (the number of batteries is 3 to 10) in the fully charged state.
The lithium ion battery is charged with joule heat, which causes an increase in battery temperature, but if it exceeds 90 ℃, abnormal overheating occurs due to structural destruction of the positive electrode active material. Therefore, as the battery temperature, it is necessary to charge the battery not more than 90 ℃ which is abnormal and within a range where the normal temperature rise can be ignored, and therefore, overcharge stability tests were performed on the battery packs of examples 5 to 9 and 15 to 18. In example 18 in which the monitoring temperature was set to 85 ℃, the maximum reaching temperature was 97 ℃, and the overcharge stability was low. In contrast, in example 15 in which the monitoring temperature was set to 50 ℃, the maximum reached temperature after the stop of charging was 52 ℃, and the overcharge stability was high, but the charging was stopped by a slight temperature rise until the fully charged state was reached, and the high-temperature charge capacity was low. It is thus understood that the monitoring temperature of the nonaqueous electrolyte secondary battery pack of the present invention is preferably 60 to 80 ℃.
From the above results, it can be seen that: the battery satisfying all of the mechanical strength, the low-temperature discharge characteristic, the high-temperature charge characteristic and the overcharge stability has the separator 6 having a porosity of 10 to 70%, the monitoring temperature is set to 60 to 80 ℃, and the number of batteries is 3 to 10, but the battery having the structure of example 7 can obtain a good result.
(examples 7A to 7F)
Then, a nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 7, except that through-holes 7 were formed in the separator 6 so that the porosity thereof was 25%, 30%, 35, 45, 50, and 55%, respectively. These were set as nonaqueous electrolyte secondary battery packs of examples 7A to 7F, respectively.
(examples 7G to 7J)
A nonaqueous electrolyte secondary battery pack was produced in the same manner as in example 7 except that the nonaqueous electrolyte secondary battery pack of example 7 was prepared such that B/a defined by the diameter a of the nonaqueous electrolyte secondary battery 1 and the distance B between the nonaqueous electrolyte secondary batteries 1 was 0.02, 0.05, 0.15, and 0.2, respectively. These were set as nonaqueous electrolyte secondary battery packs of examples 7G to 7J, respectively.
(examples 7K to 7L)
A nonaqueous electrolyte secondary battery pack of example 7 was produced in the same manner as in example 7 except that the material of the separator 6 was UNILATE (a mixture of polyethylene terephthalate, glass fiber, and mica, trade name of kyoo corporation) and PPO (polyphenylene oxide). These were set as nonaqueous electrolyte secondary battery packs of examples 7K to 7L, respectively.
(vi-c) activated Charge-discharge
For the nonaqueous electrolyte secondary battery packs of examples 7A to 7L, the charging voltage of each unit cell was controlled in an environment of 25 ℃, constant-current charging was performed at a charging current of 2A until the fastest one unit cell reached 4.2V, and then constant-voltage charging was performed until the charging current was reduced to 200 mA. After 20 minutes of rest, the discharge was carried out to 2.5V at a current value of 25A.
The following evaluations were performed on each nonaqueous electrolyte secondary battery pack after activation and charge/discharge.
(Low temperature discharge test)
After charging under the same conditions as the above-described activation charging and discharging, each nonaqueous electrolyte secondary battery pack was left to stand in an environment at 0 ℃ for 5 hours, and then discharged at a current value of 25A to 2.5V in an environment at 0 ℃. The discharge capacity thereof is shown in table 3.
(high temperature Charge test)
Charging was performed under the same conditions as the above-described activation charging and discharging except that the ambient temperature was set to 40 ℃, and the charging was stopped when the battery temperature reached the monitoring temperature. The charging capacity is shown in table 3.
(vibration stability test)
Each nonaqueous electrolyte secondary battery pack is vibrated at an oscillation frequency of 10 to 30Hz and an amplitude of 3mm for 30 minutes in an environment at 25 ℃. Vibration of the nonaqueous electrolyte secondary battery pack in the longitudinal direction and the lateral direction was repeated 3 times, respectively. Then, each nonaqueous electrolyte secondary battery pack was decomposed, and changes in the distance between the batteries before and after the vibration test were confirmed. The results are shown in Table 3, in which the change observed with the naked eye appeared and the expression was "large shift"; no change was observed with the naked eye but a change of 0.1mm or more was observed as measured with a vernier caliper, which was indicated as "small movement"; changes below 0.1mm are indicated as "no movement".
(overcharge stability test)
The nonaqueous electrolyte secondary battery packs of examples 7A to 7F were subjected to a charge test of 8A in an environment of 25 ℃, and the charging was stopped when the charge/discharge stop temperature set for each nonaqueous electrolyte secondary battery pack was reached. The maximum reached temperature after the stop displayed by the measurement unit 3 is shown in table 3.
TABLE 3
Number of batteries Arrangement of B/A Partition board Pore shape void fraction Monitoring temperature (. degree.C.) Low temperature discharge capacity (Ah) High temperature charging capacity (Ah) Stability to vibration Maximum arrival temperature
Example 7A 4 Transverse direction 0.1 ABS 25% of holes 60 2.04 2.41 Without movement 66
Example 7B 4 Transverse direction 0.1 ABS The hole is 30% 60 2.04 2.40 Without movement 63
Example 7C 4 Transverse direction 0.1 ABS 35% of holes 60 2.05 2.41 Without movement 63
Example 7D 4 Transverse direction 0.1 ABS 45 percent of holes 60 2.05 2.40 Without movement 62
Example 7E 4 Transverse direction 0.1 ABS 50% of holes 60 2.05 2.40 Without movement 61
Example 7F 4 Transverse direction 0.1 ABS Holes are 55% 60 2.04 2.39 Mobile small 62
Example 7G 4 Transverse direction 0.02 ABS 40% of holes 60 2.07 2.32 Without movement
Example 7H 4 Transverse direction 0.05 ABS 40% of holes 60 2.05 2.37 Without movement
Example 7I 4 Transverse direction 0.15 ABS 40% of holes 60 2.03 2.41 Without movement
Example 7J 4 Transverse direction 0.2 ABS 40% of holes 60 1.97 2.42 Without movement
Example 7K 4 Transverse direction 0.1 UNILATE 40% of holes 60 2.08 2.40 Without movement
Example 7L 4 Transverse direction 0.1 PPO 40% of holes 60 2.07 2.39 Without movement
The following results were obtained from examples 7A to 7F: even if the area ratio of the through-holes 7 in the separator 6 is set to 25 to 55%, the low-temperature discharge capacity and the high-temperature charge capacity are not significantly different from those of example 7. However, in example 7F having a porosity of 55%, the mechanical strength was somewhat lowered, and therefore the vibration stability was not so good as compared with examples 7A to 7E. From this, it is preferable to set the porosity to 25 to 50%.
The following results were obtained from examples 7G to 7J: when the diameter of the cylindrical nonaqueous electrolyte secondary battery 1 is set to be A and the distance between the side surfaces of the battery is set to be B, even if the relationship B/A is set to be 0.02 to 0.2, the low-temperature discharge capacity and the high-temperature charge capacity are not significantly different from those of example 7. However, in example 7H in which the B/a was set to 0.15 by slightly enlarging the distance between the cells and in example 7I in which the B/a was set to 0.2, the low-temperature discharge capacity was slightly reduced, and in example 7G in which the B/a was set to 0.02 by slightly shortening the distance between the cells and in example 7H in which the B/a was set to 0.05, the high-temperature charge capacity was slightly reduced. Thus, it can be seen that: when the diameter of the cylindrical nonaqueous electrolyte secondary battery is set to A and the distance between the battery side surfaces is set to B, the relationship B/A is more preferably set to 0.1.
In the above-described embodiment, the battery container 2 is made of ABS resin, and the separator 6 is also made of ABS resin, but in order to make the joule heat in the battery container 2 uniform and not to dissipate excessive joule heat outside the battery container 2, the separator 6 is preferably made of a material having a higher thermal conductivity than the material of the battery container 2. In contrast to 0.1 to 0.18W/mK in thermal conductivity of ABS resin, UNILATE, which is a material for the separator 6 of example 7K, and PPO, which is a material for the separator 6 of example 7L, have thermal conductivity of 0.25W/mK or more, so that Joule heat in the battery container 2 is excellent in uniformity in examples 7K to 7L, and low-temperature discharge capacity is slightly higher than that in example 7. Thus, it can be seen that: more preferably, the material of the separator 6 is UNILATE and PPO.
In addition, the nonaqueous electrolyte secondary battery packs of examples 7A to 7F were subjected to the overcharge stability test, and as a result, in any of the battery packs, the maximum reached temperature after the stop of charging did not exceed 90 ℃.
As shown in fig. 5A to 5C, the separator 6 may be used in place of the separator 6 having a large number of circular through holes 7 as shown in fig. 3, in which the separator 6 includes notches 7 having various shapes and has a porosity that facilitates uniform joule heat in the battery container 2.
As described above, the nonaqueous electrolyte secondary battery pack of the present invention has high volumetric efficiency due to the reduction of the cooling path, and maintains a good balance between heat storage and heat dissipation, so the nonaqueous electrolyte secondary battery pack of the present invention can be used as a power source for machines for outdoor use, such as electric tools, electric mopeds, electric children's scooters, robots, and the like, regardless of the environment.
The embodiments of the present invention described above are intended to illustrate the technical contents of the present invention, and are not intended to limit the technical scope, and the present invention can be implemented in various modifications within the scope described in the claims below.

Claims (4)

1. A nonaqueous electrolyte secondary battery pack, comprising: a cylindrical nonaqueous electrolyte secondary battery having a lid surface and a bottom surface provided with positive and negative electrode terminals, a battery container for containing a plurality of the nonaqueous electrolyte secondary batteries, a measurement unit for measuring a battery voltage and a battery temperature, and a control unit for controlling charging and discharging based on a measurement result of the measurement unit; wherein,
in the battery container, all the cylindrical nonaqueous electrolyte secondary batteries are arranged with side surfaces facing each other and electrically connected;
a separator having through holes and/or notches for separating adjacent side surfaces of the nonaqueous electrolyte secondary battery;
and when the diameter of the cylindrical nonaqueous electrolyte secondary battery is defined as A and the distance between the side surfaces of the battery is defined as B, the ratio B/A is in the range of 0.02 to 0.2.
2. The nonaqueous electrolyte secondary battery pack according to claim 1, wherein an area ratio of the through-holes and/or the notches in the separator to the separator is 10 to 70%.
3. The nonaqueous electrolyte secondary battery pack according to claim 2, wherein the voltage at which the nonaqueous electrolyte secondary batteries are connected in series in a fully charged state is 12.6 to 42V.
4. The nonaqueous electrolyte secondary battery pack according to claim 2, wherein the control portion has a monitoring function of stopping charge and discharge when the measurement portion on the surface of the nonaqueous electrolyte secondary battery reaches a predetermined temperature; the preset temperature is within the range of 60-80 ℃.
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