JP5838073B2 - Cylindrical wound battery - Google Patents

Description

  The present invention relates to a cylindrical wound battery.

  Among secondary batteries, lithium-ion batteries that have the advantages of high energy density and low self-discharge include power supplies for various portable devices, industrial and consumer devices, automotive power supplies, power storage power supplies, etc. The range of use is being expanded.

  The structure of the charge / discharge part of the lithium ion battery is usually a stacked type in which a separator is sandwiched between a positive electrode and a negative electrode, and a pole material and a separator are arranged in a stacked manner, and a wound type wound in a spiral shape. . The wound battery has a large effective electrode area in a small volume in order to increase the capacity and output.

  Generally, carbon materials such as non-graphitizable carbon and graphite are used as the negative electrode active material for lithium ion batteries. Recently, certain metals have been electrochemically alloyed with lithium, and this is produced reversibly. Patent Document 1 introduces an attempt to suppress expansion by alloying tin and silicon as a method of improving alloy negative electrode materials and cycle characteristics by applying decomposition. Many of these negative electrode materials are known to have large expansion / contraction due to adsorption / desorption of lithium ions.

JP 2008-262777 A

  However, when an electrode is fabricated using the negative electrode material as described above to form a battery, the negative electrode active material expands and contracts during charge and discharge, and as a result, uneven stress distribution occurs in the wound body, There has been a problem that the electrolyte is discharged by being pressed, the negative electrode mixture is peeled off from the current collector, or the negative electrode mixture is cracked and deteriorated. In addition, when an internal short circuit or the like occurs for some reason as the output of the battery increases, there is a possibility that a large current flows and the damage scale is expanded.

  In order to solve these problems, in Patent Document 1, in the wound body having a flat cross section, the positive electrode is divided in the winding direction and is constituted by a plurality of members insulated from each other, thereby causing an abnormal short circuit reaction. It is disclosed that the stress inside the wound body due to expansion and contraction accompanying charge / discharge can be reduced.

  However, this method is effective for stress relaxation measures in the winding direction of the wound body and the stress relaxation of the wound body having a flat cross-sectional shape. In the case of a long wound body, the stress relaxation effect may be small. In fact, as a result of disassembling the battery that deteriorated due to charge and discharge and examining the damaged part of the electrode, the negative electrode mixture layer, which has large expansion and contraction due to adsorption / desorption of lithium ions, is discharged into the electrolyte layer and the mixture layer due to compression action Since the active material is isolated and deteriorated due to cracking, the deteriorated part is concentrated in the central part in the axial direction of the cylindrical wound body, and the upper and lower end parts are healthy. It was found that stress concentration occurred in the central part in the axial direction.

  The problem to be solved by the present invention is that in a cylindrical wound body, the axial stress generated in the wound body during charge / discharge is relaxed to prolong the life of the battery and cause an internal short circuit for some reason. But it is to make external damage as small as possible.

The features of the present invention for solving the above-described problems are as follows.
(1) It has an electrode group having a positive electrode having a positive electrode mixture layer, a negative electrode having a negative electrode mixture layer, a separator formed between the positive electrode and the negative electrode, and a battery can containing the electrode group. In the cylindrical wound battery, the positive electrode, the negative electrode, and the separator constituting the electrode group are wound, and in the winding axis direction of the electrode group, a plurality of electrode groups are housed in a battery can, A cylindrical wound battery in which the plurality of electrode groups include a lowermost electrode group and an uppermost electrode group, and an insulating plate is inserted between each of the plurality of electrode groups.
(2) In the above, in the winding axis direction of the electrode group, a battery lid is provided on the top of the battery can, a positive electrode lead and a negative electrode lead are formed in each of the plurality of electrode groups, and each of the plurality of electrode groups Are connected by a positive electrode lead, each of the plurality of electrode groups is connected by a negative electrode lead, and in the winding axis direction of the electrode group, the negative electrode lead of the lowermost electrode group is connected to the battery can. A cylindrical wound battery in which the positive electrode lead of the uppermost electrode group is connected to the battery lid in the axial direction.
(3) In the above, the cylindrical wound battery in which the length of the electrode group is equal to or less than the diameter of the electrode group in the winding axis direction of the electrode group.
(4) In the above, a cylindrical wound battery in which the diameter of the insulating plate is not less than the outer diameter of the electrode group and not more than the inner diameter of the battery can.
(5) In the above, in the winding axis direction of the electrode group, the lowermost insulating plate is inserted between the lowermost electrode group and the battery can, and a hole is provided in the lowermost insulating plate. A cylindrical wound battery in which the negative electrode lead in the group is bent in the direction in which the hole in the lowermost insulating plate exists.
(6) A cylindrical wound battery in which a fuse or a PTC thermistor is incorporated in one of the positive electrode lead and the negative electrode lead.
(7) In the above, in the winding axis direction of the electrode group, a positive electrode current collector and a negative electrode current collector are formed between each of the plurality of electrode groups, and the positive electrode current collector has a positive electrode mixture layer. It is uncoated, and the negative electrode current collector layer is not coated on the negative electrode current collector, and the positive electrode current collector layer is not coated on the positive electrode current collector, or the negative electrode current mixture layer on the negative electrode current collector Is a cylindrical wound battery in which the curvature is provided in the uncoated part.

  According to the present invention, since the uneven stress distribution inside the wound body caused by charging and discharging can be relaxed, an effect of extending the cycle life can be obtained. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

FIG. 3 is a longitudinal sectional view of a cylindrical lithium ion secondary battery. The external view of the electrode group installed in the uppermost part of FIG. The external view of the electrode group installed in the intermediate part of FIG. The external view of the electrode group installed in the lowest part of FIG. The figure which shows the shape of the insulating board installed in the upper-lower end surface of an electrode group. The figure which shows the shape of the insulating board installed in the upper-lower end surface of an electrode group. The figure which shows the shape of the insulating board installed in the upper-lower end surface of an electrode group. The figure which shows an example of the longitudinal cross-sectional shape which connected the some electrode group. The figure which shows the other Example of the longitudinal cross-sectional shape which connected the some electrode group. The figure which shows the other Example of the longitudinal cross-sectional shape which connected the some electrode group. FIG. 8 is a simplified diagram showing the electrode configuration and winding method of FIG. 7. The A section aa cross-sectional enlarged view of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various modifications by those skilled in the art are within the scope of the technical idea disclosed in this specification. Changes and modifications are possible. In all the drawings for explaining the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.

  One embodiment of the present invention is to alleviate the stress distribution, particularly in the axial direction, of an electrode group wound in a cylindrical shape in order to increase the capacity and output of a battery. Specifically, the long electrode group in the axial direction is provided with a region that does not cause a battery reaction, and this region is used to absorb the axial elongation generated in the battery reaction part to relieve the generated stress. . Here, in order to provide a region where no battery reaction occurs, (1) a method of manufacturing a short electrode group in the axial direction and connecting a plurality of positive electrodes and negative electrodes with conductive leads, (2) or an active material This can be achieved by using a positive electrode and a negative electrode in which the mixture is divided and coated in the axial direction, and forming a group of electrodes wound so that the positive electrode and the negative electrode face each other via a separator.

FIG. 1 is a longitudinal sectional view of a cylindrical lithium ion secondary battery. As a method of (1) for providing a region in which the battery reaction does not occur in the axial direction of the electrode group, as shown in the longitudinal sectional view of FIG. 1, the cylindrical lithium ion battery 1 of this embodiment has a positive electrode and a negative electrode with separators. A plurality of short electrode groups 2 wound so as to face each other are installed in the battery can 4 with the electrical insulating plate 3 interposed therebetween. The negative electrode lead 9 of the lowermost electrode group 2 is welded to the bottom of the battery can 4 with the lower insulating plate 6 interposed therebetween, and the uppermost positive electrode lead 8 is welded to the battery lid 7 with the upper insulating plate 5 interposed therebetween, so After the injection, the battery lid 7 is caulked at the top of the battery can 4 via the gasket 10.
As the positive electrode active material and the negative electrode active material, those that repeatedly expand and contract by absorbing and releasing magnesium ions and sodium ions may be used in addition to those that repeatedly expand and contract by absorbing and releasing lithium ions. .

  The negative electrode is configured by forming a negative electrode mixture layer on a negative electrode current collector. The negative electrode mixture layer is composed of a negative electrode active material, an arbitrary conductive agent, and a binder.

  As the negative electrode active material, graphite or amorphous carbon capable of electrochemically occluding and releasing lithium ions can be used, but there is no limitation on the type and material as long as lithium ions can be occluded and released. Since the negative electrode active material to be used is generally used in a powder state, the binder is mixed to bond the powders together, and at the same time, the layer made of the negative electrode active material is bonded to the negative electrode current collector as a mixture layer I am letting.

  The conductive assistant has conductivity and does not substantially store lithium ions, but coke, carbon black, acetylene black, carbon fiber, ketjen black, carbon nanotube, mesocarbon microbead, vapor grown carbon fiber, etc. The carbon material may be used.

  As the binder, in addition to polyvinylidene fluoride (PVDF), a fluorine-based polymer such as polytetrafluoroethylene, styrene butadiene rubber (SBR), acrylonitrile rubber, or the like may be used. Other binders not listed above may be used as long as they do not decompose at the reduction potential of the negative electrode and do not react with the nonaqueous electrolyte or the solvent in which it is dissolved. A known solvent suitable for the binder may be used as the solvent used for preparing the negative electrode slurry. For example, a known solvent such as water in the case of SBR, acetone, toluene or the like can be used in the case of PVDF.

  The negative electrode current collector is required to be made of a material that is difficult to be alloyed with lithium, and there is a metal foil made of copper, nickel, titanium, or an alloy thereof. In particular, copper foil is frequently used.

  The negative electrode is prepared by adhering a negative electrode slurry in which a negative electrode active material, a conductive agent, a binder, and an organic solvent are mixed to the negative electrode current collector by a doctor blade method or the like, and then heating to dry the organic solvent and applying it by a roll press. It can be produced by pressure forming. The negative electrode mixture layer is produced on the negative electrode current collector by drying the organic solvent of the negative electrode slurry.

  The positive electrode is configured by forming a positive electrode mixture layer on a positive electrode current collector. The positive electrode mixture layer 8b includes a positive electrode active material, an arbitrary conductive agent, and a binder.

The positive electrode active material is made of an oxide containing lithium. Examples of the oxide containing lithium include an oxide having a layered structure such as LiCoO ₂ , LiNiO ₂ , LiMn _1/3 Ni _1/3 Co _1/3 O _1/3 , LiMn _0.4 Ni _0.4 Co _0.2 O _2. , Lithium manganese composite oxides having a spinel structure such as LiMn ₂ O ₄ and Li _{1 + x} Mn _2−x O ₄ , or a part of Mn in these oxides other elements such as Al and Mg The one substituted with can be used.

  Since the positive electrode active material generally has high resistance, the electrical conductivity of the positive electrode active material is supplemented by mixing carbon powder as a conductive agent. Since the positive electrode active material and the conductive agent are both powders, a binder is mixed to bond the powders together, and at the same time, this powder layer is adhered to the positive electrode current collector as a positive electrode mixture layer. As the conductive agent, natural graphite, artificial graphite, coke, carbon black, amorphous carbon, or the like can be used. When the average particle diameter of the conductive agent is smaller than the average particle diameter of the positive electrode active material powder, the conductive agent tends to adhere to the surface of the positive electrode active material particles, and the electrical resistance of the positive electrode is often reduced by a small amount of the conductive agent. Therefore, the material for the conductive agent may be selected according to the average particle diameter of the positive electrode active material.

  The positive electrode current collector may be any material that is difficult to dissolve in the electrolyte, and aluminum foil is frequently used.

  The positive electrode can be produced by a method in which a positive electrode slurry in which a positive electrode active material, a conductive agent, a binder, and an organic solvent are mixed is applied to a positive electrode current collector using a blade, that is, a doctor blade method. The positive electrode slurry applied to the positive electrode current collector is heated to dry the organic solvent, and pressure-molded by a roll press. The positive electrode mixture layer is produced on the positive electrode current collector by drying the organic solvent of the positive electrode slurry. In this manner, a positive electrode in which the positive electrode mixture layer and the positive electrode current collector are in close contact with each other can be produced.

  The electrode group 2 has an axial length that is as short as the diameter of the electrode group 2 or less, and the electrode groups 2 are joined to each other at the insulating plate 3 between the positive electrode leads 8 and the negative electrode leads 9. Has been. In FIG. 1, the length of the electrode group 2 in the axial direction is substantially the same, but it may be different.

  The appearance of the electrode group 2 is shown in FIGS. FIG. 2 is an external view of an electrode group installed at the top of FIG. FIG. 3 is an external view of an electrode group installed in the middle part of FIG. FIG. 4 is an external view of an electrode group installed at the bottom of FIG.

  The electrode group 2 in FIG. 2 is wound so that the positive electrode and the negative electrode face each other with a separator interposed therebetween, and is finished with a winding tape 11 disposed at the top of the electrode group 2 divided during assembly. It is what is done. The positive electrode lead 8 is drawn out from the uppermost and lower surfaces of the electrode group 2 from the innermost peripheral portion of the electrode group 2, and the negative electrode lead 9 is drawn out to the lower surface of the electrode group 2 in the outermost peripheral portion.

  On the other hand, the electrode group 2 in FIG. 3 is arranged in the middle during assembly, and the positive electrode lead 8 is pulled out from both the uppermost surface and the lower surface of the outermost peripheral portion of the electrode group 2. It is. Further, the electrode group 2 in FIG. 4 is arranged at the lowermost end during assembly. The positive electrode lead 8 and the negative electrode lead 9 are drawn on the upper surface, and only the negative electrode lead 9 is drawn from the lower surface.

  5A to 5C are views showing the shape of the insulating plate 3 installed on the upper and lower end surfaces of the electrode group 2. Since the electrode group 2 is stacked, in order to prevent an electrical short circuit between the upper and lower surfaces of the electrode group 2, it is necessary to sandwich an insulating plate 3 made of, for example, polypropylene, polyethylene, polyimide, or polyester. As shown in FIG. The insulating plate 3 is disk-shaped, and has a hole 31 in the center, and is provided with a cut 32 for taking out the positive electrode lead 8 and a cut 33 for taking out the negative electrode lead 9. In consideration of insulation of the plurality of electrode groups 2, the diameter of the insulating plate 3 is preferably set to be not less than the outer diameter of the electrode group 2 and not more than the inner diameter of the battery can 4. The negative electrode lead 9 may be taken out through the notch 32 and the positive electrode lead 8 may be taken out through the notch 33. However, in the case of a cylindrical battery, the battery lid 7 side is connected as the positive electrode and the battery can 4 side is connected as the negative electrode as in the case of a general battery. Therefore, it is desirable to take out the positive electrode lead 8 through the notch 32 and take out the negative electrode lead 9 through the notch 33. The central hole 31 is a hole through which the welding electrode rod is passed.

  As a variation of FIG. 5A, the insulating plate 3 may be formed as shown in FIG. 5B or FIG. 5B and 5C, the notch 33 is formed so as to face the center of the insulating plate 3. Compared to the insulating plate 3 in FIG. 5A, the insulating plate 3 in FIG. 5B or FIG. 5C can secure an insulating area.

FIG. 6 shows an example in which the electrode group 2 of the battery of the present invention is configured with the parts shown in FIGS.
The intermediate electrode group 2 of FIG. 3 is arranged on the lowermost electrode group 2 shown in FIG. 4 to join the positive electrode leads 8 (joint part 108) and the negative electrode leads 9 (joint part 109). ), And the insulating plate 3 of FIG. The number of connections of the intermediate electrode group 2 is determined according to the output characteristics and shape of the battery, and the electrode group 2 of FIG. 2 is arranged at the uppermost end. In FIG. 6, the thickness of the insulating plate 3 inserted between the electrode groups 2 is substantially the same, but may be different.

  In the wound battery of the present invention, is the axial length of the electrode group 2 that repeats expansion / contraction by reversibly occluding and releasing lithium ions by charging / discharging of the battery substantially equal to the diameter of the electrode group 2? It is preferable to make it lower. Obtaining the required battery characteristics can be easily achieved by connecting a plurality of short wound bodies in the axial direction with electrode leads.

  Next, FIGS. 7A to 7B show another embodiment of a vertical cross-sectional shape in which a plurality of electrode groups 2 are connected. As a method of (2) providing a region in which no battery reaction occurs in the axial direction of the electrode group, a positive electrode mixture coating portion 72 and a negative electrode mixture coating portion 74 in which the active material mixture is divided and applied in the axial direction are used. 4 is a partial cross-sectional view of the electrode group 2 wound so that the positive electrode mixture coating portion 72 and the negative electrode mixture coating portion 74 are opposed to each other via the separator 76. FIG.

  In this figure, on the side of the negative electrode mixture coating portion 74 that is greatly expanded and contracted due to charge and discharge, the negative electrode mixture provided between the adjacent negative electrode mixture coating portion 74 and the negative electrode mixture coating portion 74 is applied. The negative electrode current collector 73 is provided with a curvature 75, and the curvature 75 can be easily deformed to absorb the expansion / contraction behavior in the axial direction generated in the battery reaction part (active material mixture coating part). It is what I did. In FIG. 7 (A), the positive electrode of the portion not coated with the negative electrode mixture provided between the adjacent positive electrode mixture coating portion 72 and the positive electrode mixture coating portion 72 also on the positive electrode mixture coating portion 72 side. The current collector 71 is provided with a curvature 75. The curvature 75 may be formed on one or both of the positive electrode current collector 71 and the negative electrode current collector 73. When the curvature 75 is formed in both the positive electrode current collector 71 and the negative electrode current collector 73, the curvature 75 may be formed in the same direction as shown in FIG. 7A, or in FIG. Thus, the curvature 75 may be formed in different directions. When the curvature 75 is formed in the same direction as shown in FIG. 7A, the insulation distance can be easily maintained even when deformed as compared with FIG. 7B.

  The shape, size, and number of curvatures of the curvature 75 provided in this electrode mixture uncoated portion are the amount of expansion / contraction due to charge / discharge of the active material mixture in the positive electrode mixture coating portion 72 and the negative electrode mixture coating portion 74, It is necessary to select according to the axial length of the electrode group to be divided, and it is necessary to have a dimensional shape that can be deformed within a range that does not transiently affect the separator 76 when the expansion amount is absorbed.

  The use of the wound secondary battery according to the present invention is not particularly limited. For example, it can be used as a power source for portable information communication devices such as a personal computer, a word processor, a cordless telephone cordless handset, an electronic book player, a cellular phone, a car phone, a handy terminal, a transceiver, and a portable wireless device. Also, as a power source for various portable devices such as portable copiers, electronic notebooks, calculators, LCD TVs, radios, tape recorders, headphone stereos, portable CD players, video movies, electric shavers, electronic translators, voice input devices, memory cards, etc. Can be used. In addition, it can be used as household electric appliances such as refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, dryers, washing machines, lighting fixtures, and toys. Moreover, it can be used as a battery for electric tools and nursing equipment (electric wheelchairs, electric beds, electric bathing facilities, etc.) regardless of whether they are for home use or business use. Furthermore, as industrial applications, as power sources for medical equipment, construction machinery, power storage systems, elevators, unmanned mobile vehicles, and mobiles such as electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, golf carts, turret vehicles, etc. The present invention can be applied as a power source. Furthermore, it is also possible to charge the battery module of the present invention with electric power generated from a solar cell or a fuel cell and use it as a power storage system that can be used outside the ground, such as a space station, spacecraft, or space base.

  Example 1 is applied to a so-called cylindrical 18650 type lithium ion battery having a diameter of about 16 mm and a length of about 65 mm, and will be specifically described below with reference to FIGS. 1 to 6 described above.

  A positive electrode mixture containing a lithium transition metal composite oxide as a positive electrode active material is applied almost uniformly to a 15 μm thick aluminum foil current collector on the positive electrode of the electrode group 2 shown in FIGS. Was cut into a strip having a width of 17 mm and a length of about 750 mm. On the other hand, a negative electrode mixture containing a carbon powder material made of graphite or the like capable of reversibly occluding and releasing lithium ions as a negative electrode active material is applied almost uniformly to a negative electrode active material on a copper foil current collector having a thickness of 10 μm. This was cut into a strip having a width of 18 mm and a length of about 800 mm. The strip-like positive electrode and negative electrode are coated with an electrode mixture at the electrode end so that the conductive leads (positive electrode lead 8 and negative electrode lead 9) come to the predetermined positions shown in FIGS. 2 to 4 after winding. Conductive leads for passing current through a non-current collector were attached with an ultrasonic welder.

  Further, as the separator, a polyethylene microporous material having a thickness in the range of about 15 to 50 μm to 30 μm and a material larger than the width of the negative electrode were selected so that the electrode would not protrude during winding. As the separator, polyolefin such as polypropylene, polyamide, polyamideimide, or the like may be used in addition to polyethylene.

  For the winding operation of these members, a winding device having a diameter of about 4 mm and a half crack structure winding shaft was used. Each electrode group 2 has two separators wound in a roll shape drawn out, sandwiched between half-cracked portions of the winding shaft, and wound by rotating the winding shaft several times. Inserted and wound. A predetermined tension was applied to the positive electrode, the negative electrode, and the separator in the direction opposite to the direction of rotation of the winding shaft to prevent the occurrence of winding deviation or loosening during winding. After the winding of the positive electrode and the negative electrode, the separator was further wound several times and cut, and the ends were stopped with a protective tape to produce an electrode group 2.

  The produced electrode group 2 was connected in the axial direction as shown in FIG. 6 to finish one battery electrode. Here, in joining the electrode groups 2, first, the positive electrode leads 8 that are inside the electrode group 2 were joined together by a resistance welding machine (joined portion 108), and folded after joining. The negative electrode lead 9 was taken out of the electrode group 2, and after inserting the insulating plate 3 between the electrode groups 2, the negative electrode lead 9 was joined by a resistance welding machine (joined part 109) and bent upward. The negative electrode lead 9 at the lowest end was bent inward so as to cover the center hole 31 of the electrode group 2, and the insulating plate 3 was sandwiched between the electrode group 2 and the electrical insulation treatment was strengthened.

  As shown in FIG. 1, the 18650 type battery electrode produced by connecting three electrode groups 2 is provided with the insulating plate 3 attached vertically with the negative electrode side down and the positive electrode side up, and the surface is nickel-plated. The battery can 4 was stored. An electrode rod of a welding resistance machine was inserted using the center hole of the electrode group 2, and the negative electrode lead 9 was welded to the bottom of the battery can 4. Next, a groove for attaching the battery lid 7 was formed in the upper part of the battery can 4, and after inserting the gasket 10 on the upper side of the groove, the positive electrode lead 8 and the battery lid 7 were welded. What was assembled so far was put into a vacuum dryer and kept in a vacuum atmosphere at 60 ° C. for about 16 hours to remove moisture adhering to the electrode group 2 and the battery can 4.

Next, it moved in the glove box of argon gas atmosphere, and inject | poured the predetermined amount electrolyte solution.
As the electrolytic solution, a solution obtained by dissolving lithium hexafluorophosphate at a concentration of 1 mol / L in a mixed solvent such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was used.
After injecting the electrolytic solution, the battery lid 7 was lightly put in the gasket 10 on the upper part of the battery can 4 and mounted on a caulking machine, and the battery can 4 was caulked and sealed.

  The battery according to the present invention in which the electrodes are divided in the axial direction has a battery capacity reduced by several% because the length is shortened compared with the battery not divided. However, the use of short electrodes divided in the axial direction has greatly improved the cycle life of the battery. This is considered to be due to the fact that the axial expansion and contraction generated during charging / discharging is enabled and the stress concentration is reduced compared to the long electrode that is not divided in the axial direction.

  In this embodiment, the cylindrical 18650 type lithium ion battery is taken up. However, the present invention is not limited to this, and the output is increased by increasing the number of connected electrode groups 2 or a large cylindrical wound lithium battery. Applicable. In a rectangular wound battery having a parallel part in the winding direction, even if the central part in the axial direction expands, this part is deformed inward or outward to relieve stress, whereas the cylindrical wound battery Since there is no deformation in the battery, the application of the present invention to a cylindrical wound battery is effective.

  Furthermore, assuming that an internal short circuit or the like occurs for some reason in some of the electrode groups 2 in the positive electrode lead 8 or the negative electrode lead 9 connecting the plurality of short electrode groups 2 installed in the axial direction in the cylindrical can, Application of a fuse that melts and cuts off the current when the specified overcurrent is reached, and a PTC (Positive Temperature Coefficient) thermistor that increases the resistance and limits the flowing current when the temperature rises can be installed near the internal short circuit location Thus, it is possible to detect an abnormal current at an early stage and interrupt the current, thereby further enhancing safety.

  Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. As in Example 1, the present invention was applied to a cylindrical 18650 type lithium ion battery.

  FIG. 8 is a simplified diagram showing the electrode configuration and winding method of FIG. 9 is an enlarged cross-sectional view taken along a line aa in FIG. The coating pattern of the active material mixture of the positive electrode and the negative electrode and the winding method for finishing the electrode group will be described with reference to FIG.

  FIG. 8 is a view of the winding portion of a winding device (not shown) as viewed from directly above. Two separators 76 are sandwiched between the half-cracked portion of the half-cracked winding shaft 81, and the separator 76 and A state immediately before the winding is started after inserting the positive electrode and the negative electrode between the separators 76 is shown. In FIG. 8, the separator 76 is not divided in the axial direction of the electrode group 2.

  The positive electrode is obtained by applying a positive electrode mixture coating portion 72 containing a lithium transition metal composite oxide, which is a positive electrode active material, on both surfaces of a positive electrode current collector 71, which is an aluminum foil having a thickness of 15 μm, in a three-stage band shape. In addition, there is an uncoated portion of the positive electrode mixture, resulting in a striped coating pattern. The coating width per step of the positive electrode mixture coating portion 72 was about 17 mm, which was substantially the same as the diameter when finished in a wound body. The width of the positive electrode mixture uncoated portion between the adjacent positive electrode mixture coated portion 72 and the positive electrode mixture coated portion 72 is equal to the coating width of the negative electrode active material mixture and the uncoated width shown below. The relative positional relationship with the width was about 4 mm. The length of the positive electrode in the winding direction was about 750 mm. Further, an uncoated portion of the positive electrode mixture was provided at the winding start portion of the positive electrode, the positive electrode conductive lead 77 was welded to this portion, and a protective tape 84 was attached thereon to insulate a part thereof.

  On the other hand, the negative electrode is a negative electrode current collector 73 including a carbon powder material made of graphite or the like capable of reversibly occluding and releasing lithium ions as a negative electrode active material on both surfaces of a negative electrode current collector 73 which is a copper foil having a thickness of 10 μm. 74 is coated in a three-stage strip shape, and a striped coating pattern between the negative electrode mixture coating part 74 and the negative electrode mixture uncoated part between the negative electrode mixture coating part 74 and It has become. The coating width per step of the negative electrode mixture coating portion 74 was about 18 mm. Moreover, the width | variety of the uncoated part which does not apply the mixture provided between the negative mix application part 74 and the negative mix application part 74 was about 3 mm. The length of the negative electrode in the winding direction was about 800 mm. Further, an uncoated portion of the negative electrode mixture was provided at the end of the negative electrode winding, and a negative electrode conductive lead 78 was welded to this portion.

The positive electrode and the negative electrode were passed through a curvature processing roll before being wound around the winding shaft 81, and a curvature 75 was processed in an uncoated portion of the electrode. FIG. 9 shows an enlarged view of the aa cross section of the curvature processing roll. The curvature processing upper roll 82 is composed of a lower roll 91 that supports the electrode from below, and an upper roll 82 provided with a convex portion 83 for processing a predetermined curvature on the roll surface. The curvature of the convex part 83 of the upper roll 82 was semi-elliptical, the radius on the major axis side was 2 mm, and the radius on the minor axis side was 0.2 mm.
While installing the upper roll 82 and the lower roll 91 on the positive electrode side and the negative electrode side of the winding device and passing the electrode between them, the curvature 75 for absorbing displacement is formed in the uncoated portions of the positive electrode and the negative electrode. The winding shaft 81 was rotated and wound. The end of the electrode group produced by winding the electrode and further winding the separator 76 was taped, and the half-cracked portion of the winding shaft 81 was taken out in the direction of the up and down arrows to form the electrode group 2. The electrode group 2 was inserted into the battery can 4, the negative electrode lead 9 was welded to the bottom of the battery can 4, the positive electrode lead 8 was welded to the battery lid 7, the electrolyte was poured into the lid, and the battery was formed.

  In the obtained battery, the battery capacity decreased by several% because the length of the battery reaction part was shorter than that of the battery in which the electrode mixture coating part was not divided. However, by providing an uncoated portion of the electrode mixture in the axial cross-sectional direction of the cylindrical wound electrode and providing a curvature at that portion, the cycle life of the battery was greatly improved. This is considered to be due to the fact that the axial expansion / contraction displacement generated during charging / discharging is absorbed by this curvature portion and the stress concentration is relaxed compared to the long electrode that is not divided in the axial direction.

  The curvature for absorbing the amount of expansion / shrinkage shown in the examples is based on the assumption that graphite is used for the negative electrode. Correspondence is possible by increasing the corresponding large curvature and the number of steps.

DESCRIPTION OF SYMBOLS 1 Cylindrical lithium ion battery 2 Electrode group 3 Insulation board 4 Battery can 5 Upper insulation board 6 Lower insulation board 7 Battery cover 8 Positive electrode lead 9 Negative electrode lead 10 Gasket 11 Winding tape 71 Positive electrode collector 72 Positive electrode mixture coating part 73 Negative electrode current collector 74 Negative electrode mixture coating part 75 Curvature 76 Separator 81 Winding shaft 82 Upper roll 83 Convex part 91 Lower roll

Claims (6)

A positive electrode having a positive electrode mixture layer;
A negative electrode having a negative electrode mixture layer;
An electrode group having a separator formed between the positive electrode and the negative electrode;
A cylindrical winding battery having a battery can that houses the electrode group,
The positive electrode, the negative electrode, and the separator constituting the electrode group are wound,
In the winding axis direction of the electrode group, a plurality of the electrode groups are housed in the battery can,
The plurality of electrode groups include a lowermost electrode group and an uppermost electrode group,
An insulating plate is inserted between each of the plurality of electrode groups ,
In the winding axis direction of the electrode group, a battery lid is provided on the battery can,
A positive electrode lead and a negative electrode lead are formed on each of the plurality of electrode groups,
Each of the plurality of electrode groups is connected by a positive electrode lead,
Each of the plurality of electrode groups is connected by a negative electrode lead,
In the winding axis direction of the electrode group, the negative electrode lead of the lowermost electrode group is connected to the battery can,
A cylindrical wound battery in which a positive electrode lead of the uppermost electrode group is connected to a battery lid in the winding axis direction of the electrode group . In claim 1,
A cylindrical wound battery in which the length of the electrode group is equal to or less than the diameter of the electrode group in the winding axis direction of the electrode group. In claim 1 or 2 ,
The diameter of the insulating plate is a cylindrical wound battery that is not less than the outer diameter of the electrode group and not more than the inner diameter of the battery can. In any one of Claims 1 thru | or 3 ,
In the winding axis direction of the electrode group, a lowermost insulating plate is inserted between the lowermost electrode group and the battery can,
A hole is provided in the lowermost insulating plate;
A cylindrical wound battery in which a negative electrode lead in the lowermost electrode group is bent in a direction in which a hole in the lowermost insulating plate exists. In any one of Claims 1 thru | or 4 ,
A cylindrical wound battery in which a fuse or a PTC thermistor is incorporated in one of the positive electrode lead or the negative electrode lead. In any one of Claims 1 thru | or 5 ,
In the winding axis direction of the electrode group, a positive electrode current collector and a negative electrode current collector are formed between each of the plurality of electrode groups instead of the positive electrode lead and the negative electrode lead ,
The positive electrode current collector layer is uncoated on the positive electrode current collector,
The negative electrode current collector layer is uncoated on the negative electrode current collector,
A cylindrical wound battery in which a curvature is provided in a portion where the positive electrode mixture layer is uncoated in the positive electrode current collector or a portion where the negative electrode mixture layer is not coated in the negative electrode current collector.