JP2005243336A - Battery equipped with spiral electrode group - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery causing no crack or no rupture in an electrode on the outermost periphery of the battery even if the battery falls, by preventing an adhesive material from overflowing from the end part of an adhesive tape when inserting an electrode group in a case can, in order to prevent the external surface of the electrode group from being bonded to the inner wall of the case can. <P>SOLUTION: This battery is equipped with the spiral electrode group 10A formed by winding a positive electrode in which a positive electrode core body of metal foil is coated with a positive electrode active material and a negative electrode in which a negative electrode core body is coated with a negative electrode active material through a separator so that they face each other. In this spiral electrode group 10A, a core body exposing part 12b where the active material is not coated is formed on the surface of its outermost periphery, adhesive tapes 31a, 32a, 33a are pasted to the core body exposing part 12b, and non-coated parts x, y where adhesive material β is not applied is formed on the peripheral rim parts of the adhesive tapes 31a, 32a, 33a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a positive electrode in which a positive electrode active material is applied to a positive electrode core made of a metal foil and a negative electrode in which a negative electrode active material is applied to a negative electrode core made of a metal foil are wound so as to face each other via a separator. The present invention relates to a battery including a spiral electrode group.

In recent years, non-aqueous electrolyte secondary batteries that are small and light and have a high capacity have come to be used as power sources for portable electronic and communication devices such as small video cameras, mobile phones, and notebook computers. Such a non-aqueous electrolyte secondary battery uses graphite capable of occluding and releasing lithium ions as a negative electrode active material, and contains lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing manganese oxide (LiMn ₂ O ₄ ), etc. The lithium-containing transition metal oxide is used as a positive electrode active material, and the battery is configured using an electrolyte solution in which a lithium salt is dissolved as a solute in an organic solvent.

  By the way, in a device in which this type of non-aqueous electrolyte secondary battery is used, the space for accommodating the battery is often a square (flat box shape), so the power generation element is accommodated in a rectangular outer can. The formed square battery is often used. Such a prismatic battery is generally manufactured as follows. That is, first, a positive electrode mixture containing a positive electrode active material is applied to a positive electrode current collector (positive electrode core) to produce a positive electrode plate, and a negative electrode current collector (negative electrode core) contains a negative electrode active material. A negative electrode mixture is applied to produce a negative electrode plate. Then, after making these positive electrode plates and negative electrode plates oppose each other via a separator, they are spirally wound to form a spiral electrode group.

In this case, as shown in Patent Document 1, in order to prevent the spiral electrode group from being unwound, a winding tape is attached to the outermost electrode to fix the outermost electrode. . Then, after pressing the spiral electrode group into a flat spiral electrode group, it is housed in a flat rectangular outer can, and a nonaqueous electrolyte is injected to make a nonaqueous electrolyte two. Next battery. As a measure against insulation, in order to prevent a short circuit at the bottom of the outer can, a tape for insulating the bottom of the can is attached to a portion of the electrode group located at the bottom of the can. Further, for the purpose of reinforcing the current collecting tab, a protective tape is attached to the current collecting tab portion.
JP-A-11-135110

  However, there is a high demand for high capacity for this type of nonaqueous electrolyte secondary battery, and in order to meet this demand, the amount of active material filled in batteries of the same size tends to increase. For this reason, a thin metal foil having a thickness of 8 to 30 μm has been used for the core body holding the active material. And if an electrode group is comprised using the electrode by which the active material which increased the filling amount as much as possible to the core which consists of such metal foil was comprised, the thickness of an electrode group will increase.

  For this reason, the volume of the electrode group which occupies in an exterior can increases, and the problem that the clearance gap (clearance) between the inner wall surface of an exterior can and the outer surface of an electrode group became small occurred. Here, when the gap (clearance) between the inner wall surface of the outer can and the outer surface of the electrode group becomes small, when the electrode group is inserted into the outer can, it is attached to the outermost surface of the electrode group When the tape is pressed, the adhesive material protrudes from the end of the tape.

  As described above, when the adhesive material protrudes from the end portion of the tape, a situation occurs in which the outer surface of the electrode group is bonded to the inner wall surface of the outer can by the protruding adhesive material. Here, when a battery with the outer surface of the electrode group adhered to the inner wall surface of the outer can falls, the battery is impacted by the drop and the electrode group moves within the battery (in the outer can). The outermost electrode bonded to the inner wall surface of the can does not move within the outer can. As a result, the stress concentrates on the inner wall surface of the outer can of the outermost electrode of the electrode group, and the electrode in this part is cracked or the electrode breaks, making it impossible to use the battery. Produced.

  Accordingly, the present invention has been made to solve the above-described problems, and prevents the adhesive material from protruding from the end of the adhesive tape when the electrode group is inserted into the outer can. It is an object of the present invention to provide a battery in which the outermost peripheral electrode is not cracked or broken even when the battery is dropped.

  In the present invention, a positive electrode in which a positive electrode active material is applied to a positive electrode core made of a metal foil and a negative electrode in which a negative electrode active material is applied to a negative electrode core made of a metal foil are wound so as to face each other via a separator. In order to achieve the above object, the outermost surface of the spiral electrode group is formed with a core exposed portion to which no active material is applied. An adhesive tape is attached to at least one part of the body exposed part, and at least one of the adhesive tapes is formed with an uncoated part where no adhesive material is applied to a part or all of the peripheral part of the tape. It is characterized by.

  Here, when an uncoated portion where no adhesive material is applied is formed on the adhesive tape, the adhesive material can be prevented from protruding from the adhesive tape when the electrode group is inserted into the outer can. This prevents the outer surface of the electrode group from being adhered to the inner wall surface of the outer can, so that it is possible to prevent stress due to the impact of dropping from being concentrated on the outermost electrode even when the battery is dropped. . As a result, it becomes possible to prevent the outermost peripheral electrode from cracking or the outermost peripheral electrode from being broken, and a battery with improved reliability can be obtained. In addition, when the outer surface of the electrode group is not adhered to the inner wall surface of the outer can, when the electrolyte solution is injected into the outer can, the electrolyte solution is between the outer surface of the electrode group and the inner wall surface of the outer can. Will be able to penetrate smoothly. For this reason, the liquid injection property in the liquid injection process is improved, and the productivity of this type of battery is also greatly improved.

  In this case, as the pressure-sensitive adhesive tape, an anti-winding pressure-sensitive adhesive tape attached to the end of the core body exposed portion of the electrode on the outermost periphery of the electrode group is used in order to prevent the electrode group wound in a spiral shape from being loosened Is desirable. In order to prevent a short circuit at the bottom of the outer can, it is desirable to use an adhesive tape for insulating the bottom of the can attached to the portion of the electrode group located at the bottom of the can. Moreover, it is desirable to use an adhesive tape for lead protection adhered to the electrode lead portion in order to protect the electrode lead. The uncoated portion of the adhesive tape is desirably formed so that the adhesive material does not protrude from the adhesive tape when the spiral electrode group is press-fitted into the outer can.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 11. However, the present invention is not limited to this embodiment, and may be appropriately changed within a range not changing the object of the present invention. It is possible to implement. 1 is a diagram schematically showing a positive electrode plate when the present invention is applied to a lithium ion battery, FIG. 1 (a) is a plan view thereof, and FIG. 1 (b) is a diagram of FIG. 1 (a). It is sectional drawing which shows an AA cross section. FIG. 2 is a diagram schematically showing the negative electrode plate, FIG. 2 (a) is a plan view thereof, and FIG. 2 (b) is a cross-sectional view showing the AA cross section of FIG. 2 (a).

  3 is a plan view schematically showing the adhesive tape, FIGS. 3A to 3C show the anti-winding adhesive tape, and FIGS. 3D to 3F are adhesives for can bottom insulation. 3 (g) to 3 (i) show a positive electrode lead protecting adhesive tape. FIG. 4 is a perspective view schematically showing an electrode group in a state where the electrode group wound in a spiral shape is pressed into a plate shape. FIG. 5 is a perspective view schematically showing the electrode group of the first embodiment in which an adhesive tape is attached to the surface of the electrode group of FIG. FIG. 6 is a perspective view schematically showing an electrode group of a second embodiment in which an adhesive tape is attached to the surface of the electrode group of FIG.

  FIG. 7 is a perspective view schematically showing an electrode group of a third embodiment in which an adhesive tape is attached to the surface of the electrode group of FIG. FIG. 8 is a perspective view schematically showing an electrode group of a fourth embodiment in which an adhesive tape is attached to the surface of the electrode group of FIG. FIG. 9 is a perspective view schematically showing an electrode group of a fifth embodiment in which an adhesive tape is attached to the surface of the electrode group of FIG. FIG. 10 is a perspective view schematically showing an electrode group of a comparative example in which an adhesive tape is attached to the surface of the electrode group of FIG. FIG. 11 is a perspective view schematically showing a cross section of a battery configured by housing the electrode group of FIGS. 5 to 10 in an outer can.

1. Positive electrode plate First, 85 parts by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5 parts by mass of graphite powder as a conductive agent, and 5 parts by mass of carbon black were mixed to prepare a positive electrode mixture. This positive electrode mixture and a vinylidene fluoride polymer as a binder dissolved in N-methyl-2-pyrrolidone (NMP) are mixed and kneaded so that the solid content is 5 parts by mass, and then a positive electrode mixture slurry Was prepared. This positive electrode mixture slurry is applied to both surfaces of a positive electrode current collector (for example, aluminum foil or aluminum alloy foil) 11 having a thickness of 20 μm by a doctor boud method, and a positive electrode mixture layer 12 is formed on both surfaces of the positive electrode current collector 11. Formed.

  Next, the positive electrode mixture layer 12 was dried and then rolled with a roller press until a predetermined thickness was obtained. Thereafter, the positive electrode plate 10 was produced by cutting into strips having a width of 40 mm. In this case, the positive electrode current collector in which the positive electrode mixture layer 12 does not exist on both surfaces of the positive electrode current collector 11 from the rear end portion of the positive electrode current collector 11 (the portion serving as the winding end portion of the spiral electrode group) to 30 mm. 11 is an exposed portion (uncoated portion of the positive electrode mixture slurry) 12a, and the portion where the positive electrode mixture layer 12 exists only on one surface of the positive electrode current collector 11 up to 60 mm (one surface of the positive electrode current collector is an exposed portion) The positive electrode mixture slurry was applied so as to be 12b.

  Further, when exposed to a positive electrode lead 13, and the positive electrode lead 13 extends from the upper end portion of the spiral electrode group, the exposed portion of the rear end portion of the positive electrode current collector 11 (uncoated positive electrode mixture slurry) Part) A substantially U-shaped cut 13a was made in 12a. When the positive electrode plate 10 is wound, the positive electrode current collector 11 is wound so that the side where the positive electrode mixture layer exists only on one side of the positive electrode current collector 11 faces the outside of the spiral electrode group. The outermost peripheral portion can be the positive electrode current collector 11, and the positive electrode current collector 11 and the inner surface of the battery outer can can be brought into contact with each other.

2. Negative electrode plate On the other hand, a natural graphite (with an Lc value of 150 Å or more and a d ₀₀₂ value of 3.38 Å or less) powder as a negative electrode active material was dissolved in N-methyl-2-pyrrolidone (NMP) in 95 parts by mass. The vinylidene fluoride polymer as a coating was mixed and kneaded so that the solid content was 5 parts by mass to prepare a negative electrode mixture slurry. The obtained negative electrode mixture slurry was applied to both surfaces of a negative electrode current collector (for example, copper foil) 21 having a thickness of 18 μm by a doctor boud method to form a negative electrode mixture layer 22. Next, after the negative electrode mixture layer 22 is dried, the negative electrode mixture layer 22 is rolled by a roller press until a predetermined thickness is obtained, then cut into a strip shape having a width of 42 mm, and the negative electrode lead 23 is welded to the end portion to form a negative electrode plate. 20 was produced.

3. Adhesive tape (1) For winding prevention Here, an adhesive tape in which a rubber-based adhesive material β as an adhesive material is applied to a base material α made of polypropylene has a predetermined size (in this example, the width is 20 mm, The adhesive tape 31 for winding prevention was cut into a height of 42 mm. In this case, as shown in FIG. 3A, the rubber-based adhesive material β uncoated portion x (in this case, 2.5 mm (x = 2.5)) at the left and right ends in the width direction. And an uncoated portion y of rubber-based adhesive material β (in this case, 1.5 mm (y = 1.5)) formed on the upper and lower ends in the height direction An adhesive tape 31a was obtained. Further, as shown in FIG. 3 (b), the uncoated portion x of the rubber-based adhesive material β only at the left and right ends in the width direction (in this case, 2.5 mm (x = 2.5)) The one formed was used as an anti-winding adhesive tape 31b. Further, as shown in FIG. 3 (c), a material in which a rubber-based adhesive material β is applied to the entire surface of the base material α is formed without forming uncoated portions at both ends in the width direction and the height direction. An adhesive tape 31c was obtained.

(2) For can bottom insulation In addition, an adhesive tape in which a rubber adhesive β as an adhesive is applied to a base material α made of polypropylene has a predetermined size (in this example, the width is 30 mm, the height Was cut to 20 mm) to obtain a can bottom insulating adhesive tape 32. In this case, as shown in FIG. 3D, the rubber-based adhesive material β is not applied to the left and right ends in the width direction x (in this case, 1.5 mm (x = 1.5)). And the bottom of the can in which the uncoated portion y (in this case, 2.5 mm (y = 2.5)) of the rubber-based adhesive material β is formed at the upper and lower ends in the height direction The insulating adhesive tape 32a was used. Further, as shown in FIG. 3 (e), an uncoated portion y (in this case, 2.5 mm (y = 2.5)) of the rubber-based adhesive material β is formed only at the upper and lower ends in the height direction. ) Was used as a can bottom insulating adhesive tape 32b. Furthermore, as shown in FIG. 3 (f), the bottom of the can is obtained by applying a rubber adhesive β to the entire surface of the substrate α without forming uncoated portions at both ends in the width direction and the height direction. The insulating adhesive tape 32c was obtained.

(3) Positive electrode lead protection Further, an adhesive tape in which a rubber-based adhesive material β as an adhesive material is applied to a base material α made of polypropylene has a predetermined size (in this example, the width is 15 mm, the height To 12 mm) to obtain a can bottom insulating adhesive tape 33. In this case, as shown in FIG. 3 (g), the uncoated portion x of the rubber-based adhesive material β at the left and right ends in the width direction (in this case, 1.5 mm (x = 1.5)) A positive electrode lead is formed by forming an uncoated portion y (in this case, 2.5 mm (y = 2.5)) of the rubber-based adhesive material β at the upper and lower end portions in the height direction. The protective adhesive tape 33a was obtained. Further, as shown in FIG. 3 (h), an uncoated portion y (in this case, 2.5 mm (y = 2.5)) of the rubber-based adhesive material β is formed only at the upper and lower ends in the height direction. ) Was used as the positive electrode lead protecting adhesive tape 33b. Further, as shown in FIG. 3 (i), the positive electrode lead is formed by applying a rubber-based adhesive material β to the entire surface of the base material α without forming uncoated portions at both ends in the width direction and the height direction. The protective adhesive tape 33c was obtained.

  In addition, as the adhesive tape 31 for winding prevention, the adhesive tape 32 for can bottom insulation, and the adhesive tape 33 for positive electrode lead protection, a base such as polyethylene, soft vinyl, polyester, polyphenylene sulfide, and fluororesin is used instead of the above-described polypropylene base material. The material α may be used, and an acrylic or silicone adhesive β may be used instead of the rubber adhesive described above.

4). Next, a separator made of a polyethylene microporous film (with a width of 44 mm and a thickness of 25 μm) 40 (see FIG. 11) between the positive electrode plate 10 and the negative electrode plate 20 produced as described above. ) And wound in a spiral shape to produce a spiral electrode group 10a. In this case, it laminated | stacked and wound so that the part which the positive electrode electrical power collector exposed may be arrange | positioned at the outermost periphery of a spiral electrode group. Thereafter, the end of the exposed portion of the positive electrode current collector on the outermost periphery of the spiral electrode group obtained and the exposed portion of the positive electrode current collector on the inner peripheral side are passed over. (31a, 31b, 31c) were attached to prevent unwinding of the spiral electrode group 10a.

  Next, pressure was applied from both sides of the spiral electrode group produced as described above to form a spiral electrode group having an elliptical cross-sectional shape as shown in FIG. At this time, the pressure of the press was controlled so that the spiral electrode group having an oval cross-sectional shape had a predetermined thickness (in this case, 4.2 mm). Note that the spiral electrode group is previously wound so that the spiral electrode group after being pressed to have a predetermined thickness has a predetermined width (in this case, 29.0 mm). The diameter was adjusted.

  Next, as shown in FIGS. 5 to 10, can bottom insulating tapes 32a, 32b, and 32c were attached to the bottom of the spiral electrode group after pressing, respectively. Next, a notch 13a, which is formed in a U-shape in the exposed portion 12a of the positive electrode current collector 11 where the positive electrode mixture layer does not exist when the positive electrode plate 10 is manufactured, extends upward from the upper end portion of the spiral electrode group. The positive electrode current collector lead 13 was formed by bending it upward. Thereafter, as shown in FIGS. 5 to 10, positive electrode lead protecting adhesive tapes 33 a, 33 b, and 33 c are respectively attached to the bent portions of the positive electrode current collecting leads 13, and the spirals in which the respective adhesive tapes are attached. The electrode groups 10A, 10B, 10C, 10D, 10E, and 10F were produced.

  Here, as shown in FIG. 5, the spiral electrode group using the winding adhesive tape 31a, the can bottom insulating tape 32a, and the positive electrode lead protecting adhesive tape 33a was defined as an electrode group 10A (first example). . Further, as shown in FIG. 6, a spiral electrode group using a winding adhesive tape 31b, a can bottom insulating tape 32b, and a positive electrode lead protecting adhesive tape 33b was defined as an electrode group 10B (second example). Further, as shown in FIG. 7, a spiral electrode group using a winding adhesive tape 31b, a can bottom insulating tape 32c, and a positive electrode lead protecting adhesive tape 33c was defined as an electrode group 10C (third example).

  Further, as shown in FIG. 8, a spiral electrode group using a winding adhesive tape 31c, a can bottom insulating tape 32b, and a positive electrode lead protecting adhesive tape 33c was defined as an electrode group 10D (fourth example). Further, as shown in FIG. 9, a spiral electrode group using a winding adhesive tape 31c, a can bottom insulating tape 32c, and a positive electrode lead protecting adhesive tape 33b was defined as an electrode group 10E (fifth embodiment). Furthermore, as shown in FIG. 10, a spiral electrode group using a winding adhesive tape 31c, a can bottom insulating tape 32c, and a positive lead protecting adhesive tape 33c was taken as an electrode group 10F (comparative example).

5). Next, as shown in FIG. 11, a rectangular outer can made of aluminum having a thickness of 0.4 mm, a height of 48 mm, a width of 30 mm, and a thickness of 5 mm, as shown in FIG. 50 were prepared. The size, material, and thickness of the rectangular outer can 50 are not limited to this, and for example, iron or iron alloy may be used. Next, after the electrode groups 10A, 10B, 10C, 10D, 10E, and 10F produced as described above are inserted from the openings of the rectangular outer can 50, the positive electrode assembly extending from the positive electrode 10 of each of the electrode groups 10A to 10F. The electric lead 13 was welded to an outer can (also serving as a positive electrode terminal) 50, and the negative electrode current collecting lead 23 extending from the negative electrode 20 was welded to the negative electrode terminal 53.

  Thereafter, after the insulating spacer 56 is disposed in the opening of the rectangular outer can 50, the sealing plate 51 is disposed on the opening of the rectangular outer can 50, and then laser light is irradiated to these joints to form the rectangular A sealing plate 51 was joined on the outer can 50. Next, after injecting a non-aqueous electrolyte from an injection port 55 provided on the sealing plate 51, the injection port 55 is sealed and sealed by a laser welding method, and the non-aqueous electrolyte secondary batteries A and B are sealed. , C, D, E.M. Each F was produced. Note that a negative electrode terminal 52 is disposed at the center of the sealing plate 51 via an insulating gasket 54, and a gas discharge valve 53 is disposed in the negative electrode terminal 52.

Here, a battery using the electrode group 10A is a battery A, a battery using the electrode group 10B is a battery B, a battery using the electrode group 10C is a battery C, and a battery using the electrode group 10D is a battery D. A battery E was formed using the electrode group 10E, and a battery F was formed using the electrode group 10F. As the non-aqueous electrolyte, 1 mol / liter of a solute composed of lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at an equal volume ratio. A non-aqueous solution was used.

In this case, as the solute dissolved in the solvent, in addition to LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCF ₃ (CF ₂ ) ₃ SO ₃ or the like may be used. As the mixed solvent, in addition to the above-mentioned mixed solvent of EC and DEC, an aprotic solvent having no ability to supply hydrogen ions, for example, propylene carbonate (PC), vinylene carbonate (VC), butylene carbonate (BC ), Γ-butyrolactone (GBL), etc., and these and dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), 1,2-diethoxyethane (DEE), 1,2-dimethoxyethane (DME), ethoxy A mixed solvent with a low boiling point solvent such as methoxyethane (EME) may be used.

6). Durability test against dropping As described above, each battery A, B, C, D, E. After preparing 5 F each (A1 to A5, B1 to B5, C1 to C5, D1 to D5, E1 to E5, F1 to F5), these batteries were charged to 4.25 V at a charge rate of 0.2 It. After being charged, the battery was discharged at a discharge rate of 0.2 It to obtain a chargeable / dischargeable battery. Thereafter, these batteries were freely dropped on the tiles from a height of 1.00 m, and the AC impedance of each battery at a frequency of 1 kHz was measured each time it was dropped once.

In this case, when these batteries were allowed to fall freely, the six faces of the rectangular batteries were directed downward in order so that no impact was applied only in a specific direction. Regarding the battery whose internal resistance suddenly increased during repeated drop tests, the cause of the increase in internal resistance was confirmed by disassembling the battery, as shown in Table 1 below. Results were obtained. In Table 1, the number of drops indicates the number of drops until the internal resistance suddenly increases.

  As is clear from the results in Table 1 above, it can be seen that the internal resistance of the batteries A1 to A5 was not changed from that before the drop test even after the drop test was performed 1000 times. On the other hand, it can be seen that the internal resistance of the batteries F1 to F5 is greatly increased by repeating the drop test about 200 to 400 times. When the outer can 50 of the battery whose internal resistance was increased was removed, the exposed portion 12b of the positive electrode current collector 11 located on the outermost periphery of the electrode group 10F was broken in any of the batteries F1 to F5. Further, the exposed portion 12b of the positive electrode current collector 11 at the outermost periphery of the electrode group 10F was adhered to the inner wall of the outer can 50 by an adhesive material protruding from the adhesive tape. Therefore, the exposed portion 12b of the positive electrode current collector 11 located on the outermost periphery of the electrode group 10F is subjected to a drop impact in a state where the exposed portion 12b is fixed to the inner wall of the outer can 50, and the electrode group on the inner side of the exposed portion 12b It is considered that the exposed portion 12b located at the boundary of the fixed exposed portion 12b has been broken during repeated dropping because it moves inside.

  In addition, for batteries B1 to B5, only one cell out of five cells showed a phenomenon in which the internal resistance suddenly increased within 1000 times, but the internal resistance remained after 1000 drop tests for other cells. It can be seen that there is no change from before the drop test. Therefore, when the battery B2 whose internal resistance has greatly increased is disassembled, the exposed portion 12b of the positive electrode current collector 11 on the outermost periphery of the electrode group 10B has not yet been completely broken, but has a large crack. I understood. When the surface of the electrode group 10B was observed, the adhesive β protruded from one side of the tape 33b (see FIG. 6), and the exposed portion 12b of the outermost positive electrode current collector 11 of the electrode group 10B was It was found that it was adhered to the inner wall. No sticking out of the adhesive β was observed from the other tapes 31b and 32b.

  Therefore, the adhesive material β is applied among the four sides of the rectangular tape to be attached to the exposed portion 12b of the outermost positive electrode current collector 11 like the tapes 31b, 32b, 33b used for the electrode group 10B. It was found that the durability against dropping is sufficiently improved even when there are only two sides that are not. In this case, in the adhesive tape 31 for winding, it is preferable that the uncoated portion x of the adhesive material β is stuck so as to be parallel to the longitudinal direction of the electrode group 10B. In addition, in the can bottom insulating tape 32 and the positive electrode lead protecting adhesive tape 33, it is desirable that the unapplied portion y of the adhesive material β is stuck in a direction parallel to the lateral direction of the electrode group 10B.

  In addition, for batteries C1 to C5, 3 out of 5 cells showed a phenomenon in which the internal resistance rapidly increased within 1000 drop tests, but the other cells had internal resistance after 1000 drop tests. It can be seen that there is no change from before the drop test. Therefore, when the batteries C3, C4, and C5 whose internal resistance was greatly increased were disassembled, the positive electrode current collector 11 at the outermost periphery of the electrode group 10C was removed by the adhesive β that protruded from the can bottom insulating tape 32c (see FIG. 7). It was found that the exposed portion 12b was broken or cracked.

  For batteries D1 to D5, one cell out of five cells showed a phenomenon in which the internal resistance suddenly increased within 1000 drop tests, but the other cells had internal resistance after 1000 drop tests. It can be seen that there is no change from before the drop test. Therefore, when the battery D4 whose internal resistance is greatly increased is disassembled, the exposed portion 12b of the outermost positive electrode current collector 11 of the electrode group 10D is exposed by the adhesive material β protruding from the winding adhesive tape 31c (see FIG. 8). It turned out that there was a crack.

  As for batteries E1 to E5, 4 cells out of 5 cells showed a phenomenon in which the internal resistance suddenly increased within 1000 times of the drop test, but 1 cell out of 5 cells also after 1000 times of drop tests. The internal resistance has not changed from before the drop test. In addition, it can be seen that the battery in which the internal resistance has rapidly increased has more drops than the batteries F1 to F5 until the internal resistance is increased, and the durability against dropping is improved more than the batteries F1 to F5. Here, when the batteries E1, E3, E4, and E5 whose internal resistance greatly increased were disassembled, the positive electrode assembly on the outermost periphery of the electrode group 10E was removed by the adhesive material β protruding from the can bottom insulating tape 32c (see FIG. 9). It was found that the exposed portion 12b of the electric body 11 was broken or cracked.

  As described above, by providing the region x or y where the adhesive material β is not applied to the periphery of the winding adhesive tape 31, the can bottom insulating tape 32, and the positive electrode lead protecting adhesive tape 33, durability against dropping of the battery is provided. It can be seen that the performance is greatly improved. In this case, for all of the tapes 31, 32 and 33, by providing the region x or y where the adhesive material β is not applied over the entire circumference, the durability is most improved, but the tape which is not applied with the adhesive material β is applied. Even if there is only one wearing place, a sufficient durability improvement effect can be obtained. In particular, as in the case of the battery D, even if the portion of the can bottom insulating tape 32 that is parallel to the lateral direction of the electrode group 10D is used as the uncoated portion y, a sufficient durability improvement effect against dropping can be obtained. Can do.

7). Measurement of Ease of Injection of Electrolyte Next, the ease of injection of the electrolytes of Battery A and Battery F produced as described above was measured as follows. That is, a non-aqueous electrolyte is filled in a container large enough to accommodate the battery A and the battery F before the injection, and the battery A and the battery F are submerged so that the injection port 55 is placed in the container. It was. At this time, a sufficient amount of the electrolytic solution was used so that the injection port 55 was not exposed on the liquid surface even after the injection. After maintaining the battery A and the battery F in such a state in a reduced pressure state for a predetermined time for each container containing the electrolytic solution, and then removing the battery A and the battery F from the container and wiping off the electrolytic solution adhering to the surface. The masses of Battery A and Battery F were measured.

Here, for each battery, the mass of each battery was measured in advance before injection of the electrolyte solution, and this mass was subtracted from the mass obtained after injection of the electrolyte solution, thereby reducing the pressure for a predetermined time. The filling amount of the electrolytic solution can be obtained. Thus, for the battery A and the battery F as described above, when the filling amount of the electrolyte solution under a reduced pressure for a predetermined time was obtained, the results shown in Table 2 below were obtained. As the non-aqueous electrolyte, 1 mol of a solute composed of lithium hexafluorophosphate (LiPF ₆ ) is added to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at an equal volume ratio as described above. A non-aqueous solution dissolved in 1 liter was used.

  As is clear from the results in Table 2 above, when the decompression time is 1 to 5 minutes, the amount of the electrolyte solution injected into the battery A is larger than that of the battery F, and the electrolyte solution can be injected in a shorter time than the battery F. It can be seen that the amount can be greatly improved. In the battery F, the adhesive material β protrudes from the adhesive tape (31c, 32c, 33c), and the exposed adhesive material β is exposed to the exposed portion 12b of the positive electrode current collector 11 on the outermost periphery of the electrode group 10F and the outer can. This is considered to be because the electrolytic solution was prevented from penetrating into the battery by being present between the inner wall and the inner wall.

  On the other hand, in the battery A, since the adhesive material β does not protrude from the adhesive tape (31a, 32a, 33a), it is considered that the time required for injecting the electrolytic solution is shortened. When the batteries A and F were disassembled after the experiment, the adhesive material β protruded from the adhesive tape (31c, 32c, 33c) in the battery F, and the protruded adhesive material β adhered to the inner surface of the outer can 50. It was. On the other hand, in the battery A, although the region where the adhesive β is applied has moved slightly upward from the original application position, the uncoated portion provided around the adhesive tape (31a, 32a, 33a) ( x, y) never protruded.

  In addition, it turns out that the difference of the injection amount of the electrolyte solution of the battery A and the battery F becomes small when pressure reduction time becomes long, and the electrolyte solution of substantially the same quantity will be injected when pressure reduction time is 8 minutes or more. This is because in the battery F, the electrolyte solution can permeate from other paths such as the separator 40 and the corner portion of the outer can 50 as the decompression time becomes longer. This indicates that if the injection time is sufficiently long, almost the same amount of electrolyte will be injected in either case. Since it is preferable to be able to be liquid, it can be said that it is necessary to prevent the adhesive material from protruding like the battery A so as not to hinder the permeability of the electrolytic solution.

  In the above-described embodiment, an example in which natural graphite is used as the negative electrode active material has been described. However, in addition to natural graphite, a carbon-based material capable of occluding and releasing lithium ions, such as carbon black, coke, and glass. Known carbon, carbon fiber, or a fired body thereof, artificial graphite, amorphous oxide, or the like may be used. Similarly, a silicon-based material that can occlude and release lithium ions, or a mixture of silicon and a carbon-based material may be used. Of course, the present invention can be applied even when lithium or an alloy mainly composed of lithium is used for the negative electrode.

In the above-described embodiment, the example in which lithium cobaltate is used as the positive electrode active material has been described. In addition to lithium cobaltate, lithium-containing transition metal composite oxides such as lithium nickelate and lithium manganate, or dioxide dioxide Metal oxides such as manganese (MnO ₂ ), vanadium pentoxide, niobium pentoxide, and metal chalcogenides such as titanium disulfide and molybdenum disulfide can also be used.

  In the above-described embodiment, an example in which a polyethylene microporous film is used as a separator has been described. However, a polyolefin microporous film such as a polypropylene microporous film can also be used as the separator. Furthermore, a nonwoven fabric separator using polyolefin fibers can also be used.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the positive electrode plate at the time of applying this invention to a lithium ion battery, Fig.1 (a) is the top view, FIG.1 (b) shows the AA cross section of Fig.1 (a). It is sectional drawing shown. FIG. 2 is a diagram schematically illustrating a negative electrode plate, FIG. 2A is a plan view thereof, and FIG. 2B is a cross-sectional view illustrating a cross section taken along the line AA of FIG. It is a top view which shows an adhesive tape typically, FIG. 3 (a)-(c) shows the adhesive tape for winding prevention, FIG.3 (d)-(f) shows the adhesive tape for can bottom insulation, Reference numerals 3 (g) to (i) denote positive electrode lead protecting adhesive tapes. It is a perspective view which shows typically the electrode group of the state which pressed the electrode group wound by the spiral shape in plate shape. It is a perspective view which shows typically the electrode group of 1st Example by which the adhesive tape was stuck on the surface of the electrode group of FIG. It is a perspective view which shows typically the electrode group of 2nd Example by which the adhesive tape was stuck on the surface of the electrode group of FIG. It is a perspective view which shows typically the electrode group of 3rd Example by which the adhesive tape was stuck on the surface of the electrode group of FIG. It is a perspective view which shows typically the electrode group of 4th Example by which the adhesive tape was stuck on the surface of the electrode group of FIG. It is a perspective view which shows typically the electrode group of 5th Example by which the adhesive tape was stuck on the surface of the electrode group of FIG. It is a perspective view which shows typically the electrode group of the comparative example by which the adhesive tape was stuck on the surface of the electrode group of FIG. It is a perspective view which shows typically the cross section of the battery comprised by accommodating the electrode group of FIGS. 5-10 in an exterior can.

Explanation of symbols

10a ... spiral electrode group, 10A, 10B, 10C, 10D, 10E, 10F ... spiral electrode group with adhesive tape attached, 10 ... positive electrode plate, 11 ... positive electrode current collector, 12 ... positive electrode mixture layer, 12a ... core exposed portion, 13 ... positive electrode lead (positive electrode current collecting tab), 20 ... negative electrode plate, 21 ... negative electrode current collector, 22 ... negative electrode mixture layer, 23 ... negative electrode lead (negative electrode current collecting tab), 31 ... Adhesive tape, α ... base material, β ... adhesive material, 31a, 31b, 31c ... anti-winding adhesive tape, 32a, 32b, 32c ... can bottom insulating tape, 33a, 33b, 33c ... positive electrode lead protecting adhesive tape, DESCRIPTION OF SYMBOLS 40 ... Separator, 50 ... Rectangular outer can, 51 ... Sealing plate, 52 ... Negative electrode terminal, 53 ... Gas discharge valve, 54 ... Insulation gasket, 55 ... Injection hole

Claims (3)

A spiral in which a positive electrode in which a positive electrode active material is applied to a positive electrode core made of metal foil and a negative electrode in which a negative electrode active material is applied to a negative electrode core made of metal foil are wound so as to face each other via a separator A battery provided with a group of electrode electrodes,
The outermost surface of the spiral electrode group is formed with a core exposed portion that is not coated with an active material,
While the adhesive tape is stuck on at least one place of the core exposed portion,
A battery provided with a spiral electrode group, wherein at least one of the adhesive tapes is formed with an unapplied portion where an adhesive material is not applied to a part or all of the peripheral portion of the tape.   The adhesive tape has at least an anti-winding adhesive tape attached to the end of the core exposed portion of the electrode on the outermost periphery of the electrode group in order to prevent the electrode group wound in a spiral shape from unwinding. Insulation adhesive tape attached to the bottom of the electrode group to prevent short circuit at the bottom of the electrode group, adhesive for lead protection attached to the electrode lead to protect the electrode lead The battery provided with the spiral electrode group according to claim 1, wherein the battery is any one, two or all of the tapes. The said uncoated part is formed so that an adhesive material may not protrude from the said adhesive tape when the said spiral electrode group is press-fitted in an armored can. A battery having a spiral electrode group.

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