JP5849927B2 - Lithium ion secondary battery and method for producing lithium ion secondary battery - Google Patents

Description

  The present invention relates to a lithium ion secondary battery including an electrode body obtained by winding a positive electrode plate having a positive electrode active material layer and a negative electrode plate having a negative electrode active material layer through a separator, and such a lithium ion secondary The present invention relates to a battery manufacturing method.

In recent years, lithium-ion secondary batteries (hereinafter also simply referred to as “batteries”) that can be charged and discharged have been used as driving power sources for vehicles such as hybrid vehicles and electric vehicles, and portable electronic devices such as notebook computers and video camcorders. Yes.
Regarding such a battery, for example, Patent Document 1 discloses a battery manufacturing method including an initial charging process and an aging process of a battery having a wound electrode body. Further, in Patent Document 2, the separator is positioned outside the ion passage portion, an ion passage portion that allows lithium ions to move between the positive electrode mixture layer and the negative electrode mixture layer facing each other, An electricity storage device in which an ion restricting portion that restricts the movement of lithium ions from the positive electrode mixture layer to the end face of the negative electrode mixture layer is disclosed.

JP 2012-84346 A JP 2009-188037 A

By the way, after charging (initial charging) a battery having a wound electrode body described in Patent Document 1 described above, if the battery is left at a high temperature of, for example, 80 ° C. or higher, the radial direction of the electrode body in the positive electrode plate It has been found that a part of the positive electrode active material layer at the outermost peripheral portion of the positive electrode located at the outermost periphery may release lithium ions too much to locally have a high positive electrode potential. The reason for this is considered as follows.
FIG. 1 shows a partially enlarged cross-sectional view of an electrode body 210 in a conventional battery 201 including a wound electrode body 210. In the electrode body 210, the positive electrode outermost peripheral portion 330 is disposed on the outermost periphery (upward in the drawing) of the electrode body 210 in the radial direction DR (upward and downward direction in FIG. 1). The outer peripheral portion 340 covers the separator 220 from the radially outer side DR1 (upward in the figure). The negative electrode outer peripheral portion 340 faces the positive electrode outermost peripheral portion 330 with the separator 220 interposed therebetween, and the separator outer peripheral portion 320 of the separator 220 is interposed between the positive electrode outermost peripheral portion 330 and the negative electrode outer peripheral portion 340. doing.

In the battery 201, the negative electrode active material layer 241 is formed wider than the positive electrode active material layer 231 when viewed in the axial direction DX (left-right direction in the figure). Accordingly, the negative electrode active material layer 341 in the negative electrode outer peripheral portion 340 is opposed to the positive electrode active material layer 331 of the positive electrode outermost peripheral portion 330 via the separator outer peripheral portion 320, and the axial direction DX more than the opposite portion 342. 1 is disposed on one side DX1 (right side in the figure) and is disposed on the other side DX2 (left side in the figure) in the axial direction DX with respect to the one side non-opposing part 343 that does not face the positive electrode active material layer 331. And the other side non-facing portion 344 that does not face the positive electrode active material layer 331.
Further, the negative electrode foil 48 and the two negative electrode active material layers 241 and 241 of the negative electrode plate 240 form a common other side end surface 240P at the end edge of the other side DX2 in the axial direction DX. Of the other side end surface 240P, one belonging to the negative electrode outer peripheral portion 340 is defined as an outer peripheral end surface 340P (see FIG. 1).

  When the battery 201 is charged, lithium ions are released from the positive electrode active material layer 231 and inserted into the negative electrode active material layer 241 through the separator 220. Accordingly, lithium ions are also released from the positive electrode active material layer 331 of the positive electrode outermost peripheral portion 330, and the first outer peripheral active material layer 341H of the negative electrode outer peripheral portion 340 (the negative electrode active materials on the front and back of the negative electrode outer peripheral portion 340) through the separator outer peripheral portion 320. Lithium ions are also inserted into the first facing portion 342H of the layers 341 and 341 facing the positive electrode active material layer 331 (see FIG. 1). Then, a part of the lithium ions inserted into the first facing portion 342H of the first outer peripheral active material layer 341H is diffused to be adjacent to the first one-side non-facing portion 343H (the one-side non-facing portion 343 described above). Of the first outer peripheral active material layer 341H) and the first other-side non-facing portion 344H (of the other-side non-facing portion 344 described above, included in the first outer peripheral active material layer 341H). Each expands (see FIG. 2).

By the way, when the electrolytic solution adheres to the outer peripheral end surface 340P of the negative electrode outer peripheral portion 340, between the two negative electrode active material layers 341 and 341 (specifically, the first outer peripheral active material layer 341H, Of the negative electrode active material layers 341 and 341 of the negative electrode outer peripheral portion 340, the second outer peripheral active material that is located radially outside the first outer peripheral active material layer 341H and does not face the positive electrode active material layer 331 with the separator 220 interposed therebetween. Between the material layer 341J), a liquid junction through the electrolytic solution is generated (see FIG. 2). Then, the lithium ions that have moved to the first other-side non-opposing portion 344H of the first outer circumferential active material layer 341H are further diffused and moved to the second outer circumferential active material layer 341J through the electrolytic solution.
Accordingly, in the portion 342HP adjacent to the first other-side non-facing portion 344H in the first facing portion 342H, more lithium ions diffuse toward the first other-side non-facing portion 344H. The concentration of lithium ions inserted into this portion 342HP decreases, and the negative electrode potential locally increases (see FIG. 3).

Then, from the portion 331P along the end portion of the other side DX2 of the positive electrode active material layer 331 (the positive electrode lead portion 39 facing the above-described portion 342HP in the positive electrode active material layer 331), further through the separator outer peripheral portion 320, Lithium ions are released.
Thus, when the battery 201 is charged, lithium ions are excessively released from the positive electrode active material at the end portion 331P of the other side DX2 of the positive electrode active material layer 331 in the positive electrode outermost peripheral portion 330, and the positive electrode potential is locally high. A state is reached (see FIG. 3).

  By the way, in the positive electrode active material particles from which lithium ions are excessively released, the transition metal constituting the positive electrode active material particles is easily ionized and eluted into the electrolytic solution. When the battery is kept at a high temperature (80 ° C. or higher) such as high-temperature aging, the eluted metal ions are the first outer peripheral active material layer 341H (site 342HP adjacent to the other non-opposing portion 344H of the opposing portion 342H). It is metallized above and precipitates in a needle shape. Thereby, when this acicular crystal penetrates a porous separator, there is a possibility that a micro short circuit may occur between the positive and negative electrodes.

As shown in FIG. 2, the negative electrode lead portion 49 where the negative electrode foil 48 is exposed is present on one side DX1 in the axial direction DX of the negative electrode outer peripheral portion 340. On the side DX1, a liquid junction due to the electrolytic solution does not occur between the first outer peripheral active material layer 341H and the second outer peripheral active material layer 341J. Therefore, the above phenomenon does not occur on one side DX1 of the positive electrode active material layer 331.
Further, in addition to a part of the positive electrode active material layer 331 of the positive electrode outermost peripheral part 330 described above, even a part of the positive electrode active material layer of the positive electrode innermost peripheral part located in the radially innermost periphery of the positive electrode plate 30, Similarly, the positive electrode potential can be locally high.

On the other hand, in the lithium ion secondary battery provided with the separator described in Patent Document 2 described above, since the separator has an ion limiting portion, lithium ions released from the positive electrode active material layer during charging pass through the separator through the negative electrode. It cannot move directly to the portion of the active material layer that does not face the positive electrode active material layer or to the end face of the negative electrode active material layer.
However, even in this lithium ion secondary battery, when it has the above-described outer peripheral end face 340P, a liquid junction occurs on the outer peripheral end face. For this reason, when high-temperature aging is performed after the lithium ion secondary battery is initially charged, the positive electrode potential of the positive electrode plate is also locally high in this lithium ion secondary battery, and there is a minute short circuit between the positive and negative electrodes. May occur.

  The present invention has been made in view of such knowledge, and provides a lithium ion secondary battery capable of suppressing the occurrence of a short circuit between positive and negative electrodes due to metal deposition on a negative electrode active material layer at a high temperature. With the goal. Moreover, it aims at providing the manufacturing method of such a lithium ion secondary battery.

One embodiment of the present invention includes an electrode body obtained by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate through a strip-shaped separator, and an electrolytic solution impregnated in the separator. The positive electrode outermost part located on the outermost periphery of the rotated positive electrode plate, the negative electrode outer peripheral part facing from the radially outer side through the separator, and the innermost positive electrode located on the innermost periphery of the positive electrode plate A lithium ion secondary battery having a negative electrode inner peripheral part facing from the radially inner side through the separator in the peripheral part, the positive electrode plate comprising a strip-shaped positive foil and both main surfaces of the positive foil A positive electrode active material layer positioned on one side in the axial direction along the winding axis, and the negative electrode plate is positioned on the other side in the axial direction on both main surfaces of the strip-shaped negative electrode foil and the negative electrode foil negative active has a material layer, the negative electrode outer peripheral portion and the negative in-electrode periphery to Has a negative intermediate portion located between said negative electrode foil and two of the negative electrode active material layer, without a common other end face at the end edge of the other side, the negative electrode active material layer through the separator And the other side non-facing portion that is adjacent to the other side of the facing portion and does not face the positive electrode active material layer, and the separator includes the positive electrode active material layer A negative electrode plate having an intervening portion interposed between the negative electrode active material layer and the opposing portion of the negative electrode active material layer opposite to the negative electrode active material layer of the other end face, the inner peripheral end surface belonging to the outer peripheral end surface and the negative in-electrode peripheral portion belonging to the negative electrode outer peripheral portion, Ri Na covered with the liquid-retaining property deterioration of the separator, the other Of the side end faces, the end face of the intermediate part belonging to the negative electrode intermediate part is the electrode. Body is the lithium ion secondary battery comprising exposed on the other side of.

In the lithium ion secondary battery described above, among the other end surface of the negative electrode plate, an outer peripheral end face and the inner peripheral end face is covered with a liquid retention property deterioration of the separator. Since the electrolyte retainability is low in the liquid retainability lowered portion, the outer peripheral end face and the inner peripheral end face covered with the liquid retainable degraded portion are 2 in comparison with the other end face on the other side that is not covered with this. The amount of the electrolyte solution that contributes to the liquid junction between the two negative electrode active material layers can be reduced. Thus , the lithium negative electrode active material layer on the side not facing the positive electrode active material layer through the separator of the two negative electrode active material layers by liquid junction in both the negative electrode outer peripheral portion and the negative electrode inner peripheral portion. It is possible to reliably prevent ions from diffusing and moving. Therefore, in the positive electrode outermost peripheral part and the positive electrode innermost peripheral part, it can suppress reliably that a metal ion elutes from the positive electrode active material particle of a positive electrode active material layer.
Thus, positive topmost outer peripheral portion and Oite the positive electrode innermost portion, the positive electrode active material particles of the positive electrode active material layer can be metal ions can be inhibited from eluting, onto the negative electrode active material layer at a high temperature Thus, a battery in which occurrence of a short circuit due to deposition of the metal is suppressed can be obtained.
However, if the other side end face of the negative electrode plate is covered with the liquid retention lowering portion of the separator, it is difficult to impregnate the negative electrode active material layer with the electrolyte from the other side of the electrode body. In particular, when the other side end face is covered with the liquid retention lowering portion over the entire negative electrode plate, the negative electrode active material layer cannot be impregnated with the electrolyte solution through the other side end face. Unevenness is likely to occur in the state.
On the other hand, in the battery described above, of the other side end surface, the outer peripheral end surface and the inner peripheral end surface are covered with the liquid retention lowering portion, but the intermediate end surface belonging to the negative electrode intermediate portion is the other side of the electrode body. Is exposed. For this reason, while elution of metal ions can be reliably suppressed in the positive electrode outermost peripheral part and the positive electrode innermost peripheral part, the electrode body can be impregnated with the electrolyte from the other side in the negative electrode intermediate part of the negative electrode plate. . Therefore, unevenness in the impregnated state of the electrolytic solution in the axial direction in the negative electrode active material layer can be suppressed.

Also, as the liquid retaining deterioration of the separator, or the corresponding portion of the separator made of porous resin and heat-shrunk by heat, reduced the porosity than intermediate portion by applying a resin or the like to the appropriate site And those having the property of repelling the relevant part without getting wet with the electrolyte.
The positive electrode outermost peripheral portion is a portion located on the outermost periphery of the wound positive electrode plate, that is, a portion forming the outermost one turn of the positive electrode plate. On the other hand, the innermost peripheral portion of the positive electrode is a portion located on the innermost periphery of the wound positive electrode plate, that is, a portion forming the innermost turn of the positive electrode plate.
The negative electrode outer peripheral portion is a portion of the wound negative electrode plate that faces the outermost positive electrode outer peripheral portion from the radially outer side via a separator. That is, the negative electrode outer peripheral portion is located on the outer side of the negative electrode active material layer with the negative electrode plate facing the positive electrode active material layer of the positive electrode outermost peripheral portion described above, and the positive electrode active material via the separator. The layer has a negative electrode active material layer that is not opposed to the layer. On the other hand, the inner periphery of the negative electrode is a portion of the wound negative electrode plate that faces the innermost peripheral portion of the positive electrode from the inner side in the radial direction via a separator. That is, the negative electrode inner peripheral part is located on the inner side of the negative electrode active material layer facing the positive electrode active material layer of the positive electrode innermost peripheral part, and the positive electrode active material layer via the separator. Is a form having a negative electrode active material layer not facing each other.

Furthermore, in any of the above lithium ion secondary batteries, the separator is formed of a separator body made of a porous resin, and a heat-resistant layer including inorganic particles formed on one main surface of the separator body. has, in the electrode body, it is arranged in the form of the separator body is the negative electrode active material layer side, the liquid retention lowered portion, lithium is the site where the upper Symbol separator body is thermally contracted ions A secondary battery is recommended.

In the battery described above, since the separator has the separator main body and the heat-resistant layer, even if the temperature in the battery rises and the separator main body melts, the heat-resistant layer prevents contact between the positive electrode plate and the negative electrode plate. it can.
Further, since the separator is arranged in the electrode body such that the separator main body is on the negative electrode active material layer side, when the separator main body is thermally contracted by heating, the entire separator is bent to the separator main body side. It is possible to easily and reliably form the liquid retainability lowering portion that covers the other end face. Thus, a battery can be obtained in which the other end face of the negative electrode plate is reliably covered with the liquid retention lowering portion in which the porosity of the entire separator is lower than that of the interposition portion.

  In addition, as an inorganic particle contained in a heat-resistant layer, an alumina, a magnesia, a zirconia, a silica etc. are mentioned, for example. Examples of the heat-resistant layer include those containing a binder such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) in addition to the inorganic particles described above.

Furthermore, another aspect of the present invention includes an electrode body obtained by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate through a strip-shaped separator, and an electrolyte solution impregnated in the separator, The plate is positioned on the innermost periphery of the positive electrode plate, on the outermost periphery of the positive electrode located on the outermost periphery of the wound positive electrode, on the outer periphery of the negative electrode facing the outer side in the radial direction via the separator A negative electrode inner peripheral portion facing from the inner side in the radial direction through the separator on the innermost peripheral portion of the positive electrode, and the positive electrode plate has a strip-shaped positive foil and both main surfaces of the positive foil. A positive electrode active material layer positioned on one side in the axial direction along the rotation axis, and the negative electrode plate comprises a strip-shaped negative electrode foil and a negative electrode active material positioned on the other side in the axial direction on both main surfaces of the negative electrode foil. It has a material layer, negative electrode in which is located between the negative electrode outer peripheral portion and the negative in-electrode peripheral portion Has a section, the negative electrode foil and two of the negative electrode active material layer, without a common other end face at the end edge of the other side, the negative electrode active material layer, the positive electrode active material layer through the separator And the other side non-facing portion that is adjacent to the other side of the facing portion and does not face the positive electrode active material layer, and the separator faces the positive electrode active material layer and the above-mentioned An intervening portion interposed between the opposing portion of the negative electrode active material layer and a liquid retainability lowering portion that lowers the retainability of the electrolytic solution than the intervening portion, and the other end face of the negative electrode plate among them, the inner peripheral end surface belonging to the outer peripheral end surface and the negative in-electrode peripheral portion belonging to the negative electrode outer peripheral portion, Ri Na covered with the liquid-retaining property deterioration of the separator, of the other side end face, the The end face of the intermediate part belonging to the negative electrode intermediate part is exposed to the other side of the electrode body. A lithium ion secondary battery production method of which is formed by, a strip of the positive electrode plate and strip of the negative electrode plate in strip form wound with a separator not having the liquid holding deterioration section, the electrode body And a reduced portion forming step of forming the liquid retention reduced portion on the separator wound in the electrode body, and a method for manufacturing a lithium ion secondary battery. .

  The above-described method for manufacturing a lithium ion secondary battery includes the above-described electrode body manufacturing step and the lowered portion forming step. For this reason, a battery in which at least one of the outer peripheral end face and the inner peripheral end face of the other side end face of the negative electrode plate is covered with the liquid retention lowering portion of the separator can be manufactured. Therefore, it is possible to suppress the elution of metal ions from the positive electrode active material particles of the positive electrode active material layer at least in either the positive electrode outermost peripheral part or the positive electrode innermost peripheral part, and on the negative electrode active material layer at a high temperature. A battery that suppresses the occurrence of a short circuit due to metal deposition on the substrate can be produced.

  Furthermore, in the above-described method for manufacturing a lithium ion secondary battery, the separator includes a separator body made of a porous resin, a heat-resistant layer including inorganic particles formed on one main surface of the separator body. In the electrode body, the separator body is arranged in a form that is on the negative electrode active material layer side, and the liquid retention lowering portion is formed by thermally shrinking the separator body by heating, The lowering portion forming step heats a protruding portion that protrudes to the other side of the other end surface of the separator that does not have the liquid retention decreasing portion wound around the electrode body, A method of manufacturing a lithium ion secondary battery in which the main body is thermally shrunk to form the liquid retention lowering portion is preferable.

  In the lowered part forming step of the battery manufacturing method described above, the protrusion of the separator wound as an electrode body is heated, and the separator main body is thermally contracted to form the liquid retention reduced part. In addition, when a separator having a separator body and a heat-resistant layer is heated, the separator body largely heat shrinks, so that it is possible to easily form a liquid retainability lowering portion that is bent toward the separator body and covers the other end face. .

  In addition, as a method of forming the liquid retention reduced portion by thermally shrinking the separator body, for example, using a heated two metal plate, a method of forming the separator protrusion by heating and shrinking, A heating device such as a heater is brought into contact with the end of the positive electrode plate (positive electrode foil) from the other side of the electrode body to heat the positive electrode foil, and the positive electrode foil gradually heated from the other side is positioned between the positive electrode plates. There is also a method in which the protruding portion of the separator to be formed is indirectly heated and thermally contracted. In addition, there is also a method in which a positive electrode foil is sandwiched and heated by a heating device such as a heater, and the protrusion is indirectly heated and thermally contracted. Furthermore, in the case of forming a heat-shrinkable portion covering the outer peripheral end face of the negative electrode outer peripheral portion, there is a method in which a heating device is brought into contact with the protruding portion of the separator from the radially outer side of the electrode body, and this is heated and thermally contracted. Can be mentioned.

It is explanatory drawing which shows the movement of the lithium ion from the positive electrode plate at the time of charge in the winding type electrode body concerning a conventional battery at the time of charge. It is explanatory drawing which shows the diffusion movement of the lithium ion in the negative electrode active material layer at the time of charge concerning the conventional battery, and between negative electrode active material layers. It is explanatory drawing which shows the distribution of the electric potential in the negative electrode active material layer concerning the conventional battery. It is a perspective view of the battery concerning an embodiment. It is a perspective view of the positive electrode plate used for the battery concerning an embodiment. It is a perspective view of the negative electrode plate used for the battery concerning an embodiment. It is sectional drawing (CC sectional view taken on the line of FIG. 4) of the battery concerning embodiment. It is a partial expanded sectional view (DD section of Drawing 7) of an outside portion among electrode bodies in a battery concerning an embodiment. It is the elements on larger scale of the inner part among the electrode bodies in the battery concerning embodiment (DD section of Drawing 7). It is explanatory drawing (the perspective view of the separator before formation used for an electrode body production process) of the manufacturing method of the battery concerning embodiment. It is explanatory drawing of an electrode body preparation process among the manufacturing methods of the battery concerning embodiment. It is explanatory drawing of a fall part formation process among the manufacturing methods of the battery concerning embodiment. It is explanatory drawing of a fall part formation process among the manufacturing methods of the battery concerning embodiment.

Next, embodiments of the present invention will be described with reference to the drawings.
First, the battery 1 according to the present embodiment will be described with reference to FIG.
The battery 1 includes a wound electrode body 10 in which a belt-like positive electrode plate 30 and a negative electrode plate 40 both extending in the longitudinal direction DA are wound through two belt-like separators 20X and 20Y, and the separator 20 It is a lithium ion secondary battery provided with the electrolyte solution 50 impregnated in (see FIG. 4). In addition to the electrode body 10 and the electrolytic solution 50, the battery 1 further includes a battery case 80 that accommodates the electrode body 10 and the electrolytic solution 50 therein, and a positive current collecting member 91 and a negative current collecting member 92 (see FIG. 4). Among these, a plate-like positive electrode current collector 91 made of aluminum and bent in a crank shape is joined to a positive electrode lead portion 39 (described later) of the positive electrode plate 30 constituting the electrode body 10. A plate-shaped negative electrode current collector 92 made of copper and bent in a crank shape is joined to a negative electrode lead portion 49 (described later) of the negative electrode plate 40 constituting the electrode body 10.

  The battery case 80 includes an aluminum battery case body 81 and a sealing lid 82. Among these, the battery case main body 81 has a bottomed rectangular box shape, and an insulating film (not shown) made of a resin and bent into a box shape is interposed between the battery case 80 and the electrode body 10. The sealing lid 82 has a rectangular plate shape, closes the opening of the battery case body 81, and is welded to the battery case body 81. Of the positive electrode current collecting member 91 and the negative electrode current collecting member 92, the positive electrode terminal portion 91A and the negative electrode terminal portion 92A, which are located at the tips, pass through the sealing lid 82, and the lid surface facing upward in FIG. Projecting from 82a. Insulating members 95 made of insulating resin are interposed between the positive electrode terminal portion 91A and the negative electrode terminal portion 92A and the sealing lid 82 to insulate each other. Further, a rectangular plate-shaped safety valve 97 is also sealed on the sealing lid 82.

The electrolytic solution 50 is a solute in a mixed organic solvent in which ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) are adjusted to a volume ratio of EC: DEC: EMC = 3: 3: 4. LiPF ₆ is added as a nonaqueous electrolyte solution with a lithium ion concentration of 1 mol / l.

The electrode body 10 has a configuration in which the positive electrode plate 30 and the negative electrode plate 40 are wound in a flat shape around the winding axis AX via two separators 20X and 20Y (see FIGS. 4 and 7). ).
As shown in the perspective view of FIG. 5, the positive electrode plate 30 constituting the electrode body 10 has a strip shape extending in the longitudinal direction DA, and is formed on an aluminum positive electrode foil 38 and both main surfaces 38F and 38F of the positive electrode foil 38. The two positive electrode active material layers 31 and 31 are formed. In the electrode body 10 wound with the positive electrode plate 30, the width direction of the positive electrode plate 30 coincides with the axial direction DX along the winding axis AX of the electrode body 10. Therefore, in the following, the positive electrode plate 30 will be described using the axial direction DX instead of the width direction.

The positive electrode plate 30 is located on the other side DX2 (upper left side in FIG. 5) of the positive electrode foil 38 in the axial direction DX, and has a positive electrode lead portion 39 in which both main surfaces 38F and 38F of the positive electrode foil 38 are exposed. (See FIG. 5).
Conversely, the positive electrode active material layer 31 of the positive electrode plate 30 is arranged on one side DX1 (lower right side in FIG. 5) in the axial direction DX on the positive electrode foil 38 (both main surfaces 38F, 38F). The positive electrode active material layer 31 includes positive electrode active material particles (not shown) made of LiNi _1/3 Co _1/3 Mn _1/3 O _2, a conductive material (not shown) made of acetylene black, polyvinylidene fluoride ( And a binder (not shown) made of PVDF.

  In addition, in the electrode body 10, the positive electrode plate 30 includes a positive electrode outermost peripheral portion 30S located on the outermost periphery of the outer side DR1 in the radial direction DR (upward in FIG. 8) and an inner side DR2 in the radial direction DR (FIG. 9). The innermost positive electrode innermost portion 30T located in the innermost and lowermost inner periphery, and the positive electrode intermediate portion 30U located between the outermost positive electrode outer peripheral portion 30S and the innermost positive electrode inner peripheral portion 30T (FIG. 8, 9). Among these, the positive electrode outermost peripheral portion 30S passes from the outer side DR1 in the radial direction DR to the negative electrode plate 40 (of which the negative electrode outer peripheral portion 40S described later) via the second separator 20Y (the second separator outer peripheral portion 20YS described later). Covered. The positive innermost peripheral portion 30T is connected to the negative electrode plate 40 (the negative inner peripheral portion 40T described later) from the inside in the radial direction DR through the first separator 20X (the first separator inner peripheral portion 20XT described below). Covered with

  Further, as shown in the perspective view of FIG. 6, the negative electrode plate 40 has a strip shape extending in the longitudinal direction DA, and is formed on the copper negative electrode foil 48 and the two main surfaces 48F and 48F of the negative electrode foil 48, respectively. Two negative electrode active material layers 41, 41. In the electrode body 10 in which the negative electrode plate 40 is wound, the width direction of the negative electrode plate also coincides with the axial direction DX of the electrode body 10 as in the positive electrode plate 30 described above. Therefore, hereinafter, the negative electrode plate 40 will also be described using the axial direction DX instead of the width direction.

The negative electrode plate 40 is located on one side DX1 of the negative electrode foil 48 in the axial direction DX, and has a negative electrode lead portion 49 in which both main surfaces 48F and 48F of the negative electrode foil 48 are exposed (see FIG. 6).
Conversely, the negative electrode active material layer 41 of the negative electrode plate 40 is disposed on the other side DX2 in the axial direction DX on the negative electrode foil 48 (both main surfaces 48F, 48F). The negative electrode active material layer 41 includes negative electrode active material particles (not shown) made of graphite and a binder (not shown) made of styrene butadiene rubber (SBR).

In Example 1, the negative electrode active material layer 41 has the dimensions in the longitudinal direction DA and the axial direction DX larger than those of the positive electrode active material layer 31. Therefore, as shown in FIGS. 6 and 8, the negative electrode active material layer 41 includes a facing portion 42 that faces the positive electrode active material layer 31 through the separator 20X (20Y), and one axial direction DX1 of the facing portion 42. Adjacent to the positive electrode active material layer 31 and the other non-facing portion 44 adjacent to the other side DX2 in the axial direction of the opposing portion 42 and not facing the positive electrode active material layer 31. including. Further, the negative electrode active material layer 41 is an inner portion located on the radially inner side in the electrode body 10 on the outer side in the longitudinal direction DA than the above-described facing portion 42, one side non-facing portion 43, and the other side non-facing portion 44. 45 and an outer portion 46 positioned radially outward in the electrode body 10 (see FIG. 6).
That is, in the negative electrode active material layer 41, the facing portion 42 is located in the center of each of the longitudinal direction DA and the axial direction DX of the negative electrode active material layer 41, and the one side non-facing portion 43, the other side non-facing portion 44, and the inside The part 45 and the outer part 46 are located in a frame shape around the facing part 42 (see FIG. 6). However, the boundaries of the facing portion 42, the one-side non-facing portion 43, the other-side non-facing portion 44, the inner portion 45, and the outer portion 46 in the negative electrode active material layer 41 are the negative electrode plate 40, the two separators 20X and 20Y, and the positive electrode. It is determined when the electrode body 10 is produced by winding the plate 30.

  Further, as shown in FIG. 6, the negative electrode foil 48 and the two negative electrode active material layers 41, 41 are formed by cutting the edge of the other side DX2 to form a common other side end face 40P. When the electrolytic solution 50 adheres to the other end face 40P, a liquid junction through the electrolytic solution 50 is generated between the two negative electrode active material layers 41 and 41 with the negative electrode foil 48 interposed therebetween.

In the electrode body 10, the negative electrode plate 40 includes a negative electrode outer peripheral portion 40S facing the positive outermost peripheral portion 30S from the outer side DR1 in the radial direction DR via the second separator 20Y, and the first separator 20X. A negative electrode inner peripheral portion 40T opposed to the positive electrode innermost peripheral portion 30T from the inner side DR2 in the radial direction DR, and a negative electrode intermediate portion 40U positioned between the negative electrode outer peripheral portion 40S and the negative electrode inner peripheral portion 40T. (See FIGS. 8 and 9).
Among these, the negative electrode outer peripheral portion 40S includes a first outer peripheral active material layer 41SH facing the positive electrode active material layer 31 of the positive electrode outermost peripheral portion 30S among the two negative electrode active material layers 41 and 41, and the first outer peripheral active material layer 41SH. It has a second outer peripheral active material layer 41SJ that is located on the radially outer side DR1 from the material layer 41SH and is not opposed to the positive electrode active material layer via the first separator 20X (first separator outer peripheral portion 20XS described later). (See FIG. 8). Among these, the first outer peripheral active material layer 41SH is adjacent to the facing portion 42SH facing the positive electrode active material layer 31 and one side DX1 of the facing portion 42SH, and does not face the positive electrode active material layer 31. Part 43SH and the other side non-facing part 44SH that is adjacent to the other side DX2 of the facing part 42SH and does not face the positive electrode active material layer 31.

  On the other hand, the negative electrode inner peripheral portion 40T includes a first inner peripheral active material layer 41TH facing the positive electrode active material layer 31 of the positive innermost peripheral portion 30T of the two negative electrode active material layers 41 and 41, and the first inner peripheral active material layer 41TH. The second inner peripheral active material that is located on the radially inner side DR2 from the inner peripheral active material layer 41TH and is not opposed to the positive electrode active material layer via the second separator 20Y (second separator inner peripheral portion 20YT described later). Layer 41TJ (see FIG. 9). Among these, the first inner peripheral active material layer 41TH is adjacent to the facing portion 42TH facing the positive electrode active material layer 31 and one side DX1 of the facing portion 42TH, and is not on one side not facing the positive electrode active material layer 31. It includes a facing portion 43TH and a second non-facing portion 44TH that is adjacent to the other side DX2 of the facing portion 42TH and does not face the positive electrode active material layer 31.

  In the electrode body 10, the outer peripheral end surface 40SP belonging to the negative electrode outer peripheral portion 40S among the other end surface 40P of the negative electrode plate 40 is covered with a first heat contraction portion 26XS and a second heat contraction portion 26YS described later. . Further, the inner peripheral end face 40TP belonging to the negative electrode inner peripheral portion 40T is covered with a first heat shrinkable portion 26XT and a second heat shrinkable portion 26YT described later (see FIGS. 8 and 9). On the other hand, the intermediate portion end face 40UP belonging to the negative electrode intermediate portion 40U is exposed on the other side DX2 of the electrode body 10 (see FIG. 8).

  On the other hand, the two separators 20X and 20Y have a separator body 20A made of porous resin and a heat-resistant layer 20B formed on one main surface 20AF of the separator body 20A. Among these, the separator main body 20A has a three-layer structure in which one porous film made of polyethylene (PE) is overlapped between two porous films made of polypropylene (PP). On the other hand, the heat-resistant layer 20B includes inorganic particles (not shown) made of alumina and a binder (not shown).

Of the two separators 20X and 20Y, the first separator 20X located on the radial outer side DR1 of the negative electrode plate 40 in the electrode body 10 is the first separator outer peripheral part located on the radial outer side DR1 of the negative electrode outer peripheral part 40S. 20XS, the 1st separator inner peripheral part 20XT located in radial direction outer side DR1 of the negative electrode inner peripheral part 40T, and the 1st separator intermediate | middle located between these 1st separator outer peripheral part 20XS and 1st separator inner peripheral part 20XT It is divided into 20XU. The first separator 20X is arranged in such a manner that the separator body 20A is located on the negative electrode plate 40 side, that is, on the radially inner side DR2, and the heat-resistant layer 20B is located on the one side DX1.
Of the two separators 20X and 20Y, the second separator 20Y located on the radial inner side DR2 of the negative electrode plate 40 in the electrode body 10 is the second separator outer circumferential part located on the radial inner side DR2 of the negative electrode outer circumferential part 40S. 20YS, the second separator inner peripheral portion 20YT located on the radially inner side DR2 of the negative electrode inner peripheral portion 40T, and the second separator intermediate portion located between the second separator outer peripheral portion 20YS and the second separator inner peripheral portion 20YT. And 20YU. The second separator 20Y is arranged in such a manner that the separator body 20A is located on the negative electrode plate 40 side, that is, the radially outer side DR1, and the heat-resistant layer 20B is located on the other side DX2.

Among these, the first separator intermediate portion 20XU of the first separator 20X includes an intervening portion 22XU interposed between the positive electrode active material layer 31 and the facing portion 42 of the negative electrode active material layer 41 facing the positive electrode active material layer 31. The one-side extension 23XU extending from the interposition part 22XU to the one side DX1 in the axial direction DX and the other-side extension part 24XU extending from the interposition part 22XU to the other side DX2 (see FIG. 8). . In addition, these interposition part 22XU, the one side extension part 23XU, and the other side extension part 24XU consist of the porous separator main body 20A and the heat-resistant layer 20B mentioned above, and can fully hold the electrolyte solution 50.
Similarly to the first separator intermediate portion 20XU, the second separator intermediate portion 20YU of the second separator 20Y also includes an intervening portion 22YU interposed between the positive electrode active material layer 31 and the facing portion 42 of the negative electrode active material layer 41. It consists of one side extension part 23YU extending from the interposition part 22YU to one side DX1, and the other side extension part 24YU extending to the other side DX2 (see FIG. 8). The intervening portion 22YU, the one-side extending portion 23YU, and the other-side extending portion 24YU are also composed of a porous separator body 20A and a heat-resistant layer 20B in the same manner as the first separator intermediate portion 20XU. Can hold enough.

  On the other hand, the first separator outer peripheral portion 20XS of the first separator 20X is located on the first main body portion 25XS composed of the separator main body 20A and the heat-resistant layer 20B and the other axial side DX2 of the first main body portion 25XS, and the heat-resistant layer 20B. And a first heat shrinking portion 26XS comprising a shrinking separator body 20C in which the resin constituting the separator body 20A is heat-shrinked (see FIG. 8). Since the shrinkage separator main body 20C forming the first heat shrinkable portion 26XS has a lower porosity than the separator main body 20A of the first main body portion 25XS, for example, the interposition portion 22XU of the first separator intermediate portion 20XU described above, etc. The retention of the electrolytic solution 50 is lower in the first heat contraction portion 26XS than in the portion of the first separator 20X having the separator body 20A.

Further, the second separator outer peripheral portion 20YS of the second separator 20X is positioned on the second main body portion 25YS composed of the separator main body 20A and the heat resistant layer 20B and the other axial side DX2 of the second main body portion 25YS, and the heat resistant layer 20B. And the second heat shrink part 26YS comprising the shrink separator body 20C described above (see FIG. 8). Among these, the second main body portion 25YS includes a positive electrode active material layer 31 of the positive electrode outermost peripheral portion 30S and a facing portion 42SH of the first outer peripheral active material layer 41SH of the negative electrode outer peripheral portion 40S facing the positive electrode active material layer 31. It is a form including the interposition part 22YS intervening between.
The shrinkage separator body 20C forming the second heat shrinkage part 26YS also has a lower porosity than the separator body 20A of the second body part 25YS, so that the second separator part 20YS is second than the interposition part 22YS included in the second body part 25YS. In the heat shrink part 26YS, the retainability of the electrolyte solution 50 is low.

  As shown in FIG. 8, the first heat contraction portion 26XS of the first separator outer peripheral portion 20XS and the second heat contraction portion 26YS of the second separator outer peripheral portion 20YS are from the outer peripheral end surface 40SP of the negative electrode outer peripheral portion 40S. Are joined to each other on the other side DX2. Specifically, the shrink separator body 20C forming the first heat shrink portion 26XS and the shrink separator body 20C forming the second heat shrink portion 26YS are thermally contracted and welded to each other. Thereby, the outer peripheral end surface 40SP is covered with the first heat shrinking part 26XS of the first separator outer peripheral part 20XS and the second heat shrinking part 26YS of the second separator outer peripheral part 20YS.

In the battery 1 of the present embodiment, not only the outer peripheral end surface 40SP of the negative electrode outer peripheral portion 40S but also the end portion on the other side DX2 of the negative electrode outer peripheral portion 40S is not limited to the first heat contraction portion 26XS and the second heat contraction portion 26YS. (See FIG. 8).
However, as a form of the 1st heat contraction part 26XS and the 2nd heat contraction part 26YS, it is good also as a form which covers only the outer peripheral part end surface 40SP of the negative electrode outer peripheral part 40S. Moreover, it is good also as a form which covers the whole other side non-facing part 44SH of 1st outer periphery active material layer 41SH other than outer peripheral part end surface 40SP with the 2nd heat contraction part 26YS.

The first separator inner peripheral portion 20XT of the first separator 20X is located on the first main body portion 25XT composed of the separator main body 20A and the heat-resistant layer 20B, and the other axial side DX2 of the first main body portion 25XT, and the heat-resistant layer. 20B and the first thermal contraction portion 26XT composed of the shrink separator body 20C described above (see FIG. 9). Among these, the first main body portion 25XT is opposed to the positive electrode active material layer 31 of the positive innermost periphery portion 30T and the first inner peripheral active material layer 41TH of the negative electrode inner peripheral portion 40T facing the positive electrode active material layer 31. It is a form including the interposition part 22XT interposed between the part 42TH.
The shrinkable separator body 20C that forms the first heat shrink part 26XT also has a lower porosity than the separator body 20A of the first body part 25XT. Therefore, the shrinkage separator body 20C is more first than the interposed part 22XT included in the first body part 25XT. In the heat shrink part 26XT, the retainability of the electrolyte solution 50 is low.

  The second separator inner peripheral portion 20YT of the second separator 20Y is positioned on the second main body portion 25YT composed of the separator main body 20A and the heat-resistant layer 20B, and on the other axial side DX2 of the second main body portion 25YT. 20B and the 2nd heat contraction part 26YT which consists of shrinkable separator main body 20C (refer FIG. 9). Since the shrinkage separator body 20C forming the second heat shrink part 26YT also has a lower porosity than the separator body 20A of the second body part 25YT, for example, the interposition part 22YU of the second separator intermediate part 20YU described above, etc. In addition, the retention of the electrolytic solution 50 is lower in the second heat contraction portion 26YT than in the portion of the second separator 20Y having the separator body 20A.

  As shown in FIG. 9, the first heat contraction portion 26XT of the first separator inner peripheral portion 20XT and the second heat contraction portion 26YT of the second separator inner peripheral portion 20YT are the inner periphery of the negative electrode inner peripheral portion 40T. They are joined to each other on the other side DX2 with respect to the part end face 40TP. Specifically, the shrink separator body 20C forming the first heat shrink portion 26XT and the shrink separator body 20C forming the second heat shrink portion 26YT are thermally contracted and welded to each other. Thereby, the inner peripheral end face 40TP is covered with the first heat shrinking part 26XT of the first separator inner peripheral part 20XT and the second heat shrinking part 26YT of the second separator inner peripheral part 20YT.

In the battery 1 of the present embodiment, not only the inner peripheral end face 40TP of the negative electrode inner peripheral portion 40T but also the end portion on the other side DX2 of the negative electrode inner peripheral portion 40T is not limited to the first heat contraction portion 26XT and the second heat. It is covered with the contraction portion 26YT (see FIG. 9).
However, as a form of the 1st heat contraction part 26XT and the 2nd heat contraction part 26YT, it is good also as a form which covers only the inner peripheral part end surface 40TP of the negative electrode inner peripheral part 40T. Further, in addition to the inner peripheral end face 40TP, the entire other side non-facing portion 44TH of the first inner peripheral active material layer 41TH may be covered with the first thermal contraction portion 26XT.

By the way, the battery 1 (n = 10) according to the present embodiment (referred to as Example 1) was subjected to the following tests in order to confirm the presence or absence of the occurrence of a micro short circuit under high temperature aging.
Specifically, self-discharge investigation was performed using the battery 1 which was subjected to initial charging and high-temperature aging immediately after production.
First, as the above-described initial charging, charging was performed at a constant current of 0.2 C under a temperature environment of 25 ° C. until the voltage between the terminals of the battery reached a predetermined charging end voltage value (= 4.4 V) ( Constant current charging). And as above-mentioned high temperature aging, the battery 1 was thrown into the thermostat which is not shown in figure, and left still for 2 days in a 80 degreeC temperature environment.
About the battery 1 after high temperature aging, the voltage between the terminals of the battery 1 was measured, and the battery having an inter-terminal voltage of 4.1 V or less was determined to be NG. Table 1 shows the number of NG (number of NG) out of n = 10.

Moreover, each battery of Examples 2-4 and Comparative Example 1 was prepared. Of these, the battery of Example 2 is the same as the battery of Example 3 in that only the outer peripheral end surface of the negative electrode outer peripheral portion of the other end surface of the negative electrode plate is covered with the thermal contraction portion of the separator. It differs from the battery 1 of Example 1 in that, of the side end surfaces, only the inner peripheral end surface of the negative electrode inner peripheral portion is covered with the thermal contraction portion of the separator. Further, the battery of Example 4 differs from Example 1 in that the other end face of the entire negative electrode plate is covered with the heat shrinkage part of the separator.
On the other hand, the battery of Comparative Example 1 differs from Example 1 in that the other side end face of the negative electrode plate was not covered with the heat shrink portion of the separator.
For each of the batteries of Examples 2 to 4 and Comparative Example 1, whether or not a short circuit occurred under high temperature aging was examined in the same manner as the battery 1 of Example 1 described above (n = 10). The results for each battery are also shown in Table 1.

  According to Table 1, while the number of NG in the battery of Comparative Example 1 was 6, the number of NG in each battery of Examples 1 to 4 was 0 to 3, and the number determined as NG was Few. Therefore, in the battery of Comparative Example 1 in which the other end surface of the negative electrode plate is not covered with the heat shrinkage portion of the separator, metal ions are extracted from the positive electrode active material particles at the positive electrode outermost periphery and the positive electrode innermost periphery during charging. It is considered that the metal ions are easily eluted and the metal ions are deposited on the negative electrode active material layer under high temperature aging, thereby causing a short circuit between the positive and negative electrodes. On the other hand, in the batteries of Examples 1 to 4 in which at least one of the outer peripheral end face and the inner peripheral end face is covered with the thermal contraction part of the separator among the other side end faces of the negative electrode plate, the battery of Comparative Example 1 is used. It can be seen that, in at least one of the positive electrode outermost peripheral portion and the positive electrode innermost peripheral portion, elution of metal ions can be prevented and occurrence of a short circuit can be suppressed.

Furthermore, in each battery of Examples 2 and 3, the number of NGs was 2 and 3, whereas in each battery of Examples 1 and 4, the number of NGs was 0. In the battery (Examples 2 and 3) in which only one of the outer peripheral end face and the inner peripheral end face is covered with the thermal contraction part of the separator among the other end faces, the thermal contraction part among the outer peripheral end face and the inner peripheral end face. On the end surface not covered with, a liquid junction occurs between the negative electrode active material layers during charging. Then, it is considered that lithium ions diffused and moved to the negative electrode active material layer on the side not facing the positive electrode active material layer due to this liquid junction, and elution of metal ions from the positive electrode active material particles occurred.
On the other hand, in the batteries (Examples 1 and 4) in which both the outer peripheral end face and the inner peripheral end face are covered with the heat shrinkage part, the liquid junction between the negative electrode active material layers is formed on the outer peripheral end face and the inner peripheral end face. The amount of the electrolyte solution that contributes to the negative electrode active material layer can be reduced, lithium ion diffusion movement to the negative electrode active material layer on the side not facing the positive electrode active material layer can be suppressed, and the occurrence of short circuits has been suppressed. I understand.

  In addition, in each battery of Examples 1-4, since the other side end surface of a negative electrode plate is covered with the heat contraction part of a separator, from the other side DX2 of the electrode body compared with the battery of the comparative example 1 which does not provide a heat contraction part. It becomes difficult to impregnate the negative electrode active material layer with the electrolytic solution 50. In particular, among the batteries of Examples 1 to 4, in the case of the battery of Example 4 in which the thermal contraction portion covers the other side end face of the entire negative electrode plate, the negative electrode active material layer is electrolyzed through the other side end face. The liquid 50 cannot be impregnated. For this reason, the battery of Example 4 is not covered with the heat shrinkage part of the other side end surface, and compared with the battery exposed to the other side DX2 of the electrode body (Examples 1 to 3), It takes a long time to impregnate the entire negative electrode active material layer with the electrolytic solution 50. In addition, in the negative electrode active material layer, it is considered that unevenness easily occurs in the impregnated state of the electrolytic solution 50 in the axial direction DX.

In each battery (battery 1) of Examples 1 to 4 according to the present embodiment, at least one of the outer peripheral end surface 40SP and the inner peripheral end surface 40TP is the separators 20X and 20Y among the other end surface 40P of the negative electrode plate 40. Are covered with heat shrinkage portions 26XS, 26XT, 26YS, and 26YT. The heat-shrinkable portions 26XS, 26XT, 26YS, and 26YT are covered with the heat-shrinkable portions 26XS, 26XT, 26YS, and 26YT, as compared with the conventional other end face that is not covered with the electrolyte solution 50 because the electrolyte solution 50 has low retainability. In the outer peripheral end face 40SP or the inner peripheral end face 40TP, the two negative electrode active material layers (the first outer peripheral active material layer 41SH and the second outer peripheral active material layer 41SJ, the first inner peripheral active material layer 41TH, and the second inner active material layer 41TH) The amount of the electrolytic solution 50 that contributes to the liquid junction between the circumferential active material layers 41TJ) can be reduced. As a result, lithium ions diffuse and move to the negative electrode active material layer (second outer peripheral active material layer 41SJ and second inner peripheral active material layer 41TJ) on the side not facing the positive electrode active material layer 31 due to the liquid junction. Can be suppressed.
Thus, at least in any one of the positive electrode outermost peripheral portion 30S and the positive electrode innermost peripheral portion 30T, the elution of metal ions from the positive electrode active material particles of the positive electrode active material layer 31 can be suppressed, and the negative electrode active at a high temperature can be suppressed. It can be set as the battery 1 which suppressed generation | occurrence | production of the short circuit by deposition of the metal on the material layer 41. FIG.

  Moreover, in each battery (battery 1) of Examples 1 and 4 in the present embodiment, the outer peripheral end face 40SP and the inner peripheral end face 40TP belonging to the negative electrode outer peripheral portion 40S and the negative electrode inner peripheral portion 40T, respectively, are heat-shrinkable portions 26XS. , 26XT, 26YS, and 26YT. For this reason, the negative electrode active material layer on the side of the two negative electrode active material layers 41 that is not opposed to the positive electrode active material layer 31 via the separator in both the negative electrode outer peripheral portion 40S and the negative electrode inner peripheral portion 40T due to liquid junction. Lithium ions can be reliably prevented from diffusing and moving to (second outer peripheral active material layer 41SJ and second inner peripheral active material layer 41TJ). Therefore, the elution of metal ions from the positive electrode active material particles of the positive electrode active material layer 31 can be reliably suppressed in the positive electrode outermost peripheral portion 30S and the positive electrode innermost peripheral portion 30T.

  Further, in the battery 1 of Example 1, the outer peripheral end surface 40SP and the inner peripheral end surface 40TP of the other side end surface 40P are covered with the heat shrink portions 26XS, 26XT, 26YS, and 26YT, but the negative electrode intermediate portion 40U. The intermediate end face 40UP to which it belongs is exposed on the other side DX2 of the electrode body 10. For this reason, while elution of metal ions can be reliably suppressed at the positive electrode outermost peripheral portion 30S and the positive electrode innermost peripheral portion 30T, in the negative electrode intermediate portion 40U of the negative electrode plate 40, the electrode body 10 is also electrolyzed from the other side DX2. Liquid 50 can be impregnated. Therefore, unevenness of the impregnation state of the electrolytic solution 50 in the axial direction DX in the negative electrode active material layer 41 can be suppressed.

Moreover, in each battery (battery 1) of Examples 1 to 4 according to this embodiment, since the separators 20X and 20Y have the separator body 20A and the heat-resistant layer 20B, the temperature in the battery 1 rises and the separator Even if the main body 20A is melted, the contact between the positive electrode plate 30 and the negative electrode plate 40 can be prevented by the heat-resistant layer 20B.
The separators 20X and 20Y are arranged in the electrode body 10 so that the separator body 20A is on the negative electrode active material layer 41 side. Therefore, when the separator body 20A is thermally contracted by heating, the separators 20X and 20Y are entirely Since it bends to the separator body 20A side, the heat-shrinkable portions 26XS, 26XT, 26YS, and 26YT that cover the other end surface 40P of the negative electrode plate 40 can be easily and reliably formed. Thus, the other side of the negative electrode plate 40 at the heat-shrinkable portion 26XS, 26XT, 26YS, 26YT having the shrinkable separator body 20C in which the porosity of the separator body 20A is lower than the interposition portion 22 (22XU, 22XT, 22YS, 22YU). It can be set as the battery 1 which covered the end surface 40P reliably.

Next, a method for manufacturing the battery 1 of this embodiment (Example 1) will be described.
First, the positive electrode plate 30 and the negative electrode plate 40 constituting the electrode body 10 were respectively produced by known methods (see FIGS. 5 and 6).
On the other hand, the first pre-formation separator 20XB and the second pre-formation separator 20YB before forming the heat shrink portions 26XS, 26XT, 26YS, and 26YT in the first separator 20X and the second separator 20Y that form the electrode body 10 are respectively produced. To do. Specifically, inorganic particles made of alumina and a binder are mixed in a solvent using a known coating device on one main surface 20AF of the separator main body 20A of a strip-like sheet made of porous resin. The paste (not shown) was applied and dried on the separator body 20A to obtain the heat-resistant layer 20B. Thus, strip-shaped first pre-formation separator 20XB and second pre-formation separator 20YB were produced (see FIG. 10).

Next, the electrode body manufacturing process will be described. The positive electrode plate 30 and the negative electrode plate 40 were wound in a cylindrical shape together with the two pre-formation separators 20XB and 20YB prepared as described above. At this time, the second pre-formation separator 20YB, the negative electrode plate 40, the first pre-formation separator 20XB, and the positive electrode plate 30 were stacked in order and wound. Therefore, the first pre-formation separator 20XB is arranged inside the positive electrode plate 30, the negative electrode plate 40 is arranged inside the first pre-formation separator 20XB, and the second pre-formation separator 20YB is arranged inside the negative electrode plate 40 (FIG. 11). On the other hand, the second pre-formation separator 20YB is disposed outside the positive electrode plate 30, the negative electrode plate 40 is disposed outside the second pre-formation separator 20YB, and the first pre-formation separator 20XB is disposed outside the negative electrode plate 40.
Further, the positive electrode lead portion 39 is positioned on one side DX1 (downward in FIG. 11) in the axial direction DX parallel to the axis line AX, and the negative electrode lead portion 49 is positioned on the other side DX2 in the axial direction DX (in FIG. 11). The positive electrode plate 30 and the negative electrode plate 40 are arranged so as to be located on the upper side. Furthermore, the separator main body 20A of the first pre-formation separator 20XB and the separator main body 20A of the second pre-formation separator 20YB are arranged in a form that is on the negative electrode active material layer 41 side of the negative electrode plate 40.
After winding, the cylindrical surface was crushed from both sides, and a flat wound electrode body 10 having an oblong shape with a flat cross section was produced.

Next, a description will be given of a lowered portion forming step for forming the heat shrinkage portions 26XS, 26XT, 26YS, and 26YT on the pre-formation separators 20XB and 20YB wound around the electrode body 10.
In this lowered portion forming step, two flat metal plates MB, MB are used (see FIG. 12). These two metal plates MB, MB are both heated and in a high temperature state (about 200 ° C.). For this reason, when these metal plates MB and MB come into contact with the separators 20XB and 20YB before the electrode body 10 is formed, the separator main body 20A at the contact portion and the vicinity thereof is thermally contracted.

In the lowered portion forming step, the protruding portions 26XB and 26YB protruding from the other side end face 40P of the negative electrode plate 40 to the other side DX2 of the negative electrode plate 40 among the pre-formation separators 20XB and 20YB using the metal plate MB described above. Heat.
In the first embodiment, one of the two metal plates MB, MB is placed on the protruding portion 26XB of the portion of the first pre-formation separator 20XB located on the radially outer side DR1 of the negative electrode outer peripheral portion 40S described above. The protrusion 26XB is heated from the radially outer side DR1 (see FIGS. 12 and 13). As a result, the protrusion 26XB and the separator body 20A in the vicinity are thermally contracted. Of the separator main body 20A and the heat-resistant layer 20B forming the first pre-formation separator 20XB, the separator main body 20A is more thermally contracted, and therefore the protrusion 26XB and the vicinity thereof are on the separator main body 20A side, that is, the negative electrode outer peripheral portion. Turn to the 40S side.
At the same time, the other metal plate MB is brought into contact with the protruding portion 26YB located at the radially inner side DR2 of the negative electrode outer peripheral portion 40S in the second pre-formation separator 20YB from the radially inner side DR2, The protrusion 26YB is heated (see FIGS. 12 and 13). As a result, the protrusion 26YB and the separator body 20A in the vicinity are thermally contracted. In the second pre-formation separator 20XB, the separator body 20A is largely thermally contracted, so that the protruding portion 26YB and the vicinity thereof are also bent toward the negative electrode outer peripheral portion 40S.

Further, the two metal plates MB, MB are brought close to each other in the radial direction DR, and the protrusion 26XB of the first pre-formation separator 20XB and the protrusion 26YB of the second pre-formation separator 20YB are sandwiched (see FIG. 13). Thereby, the separator main body 20A of the protrusion 26XB of the first pre-formation separator 20XB and the separator main body 20A of the protrusion 26YB of the second pre-formation separator 20YB are thermally contracted and welded. Thus, the first heat shrinkage part 26XS described above is formed in the first pre-formation separator 20XB, and the second heat shrinkage part 26YS described above is formed in the second pre-formation separator 20YB (see FIG. 8).
Similarly, for the pre-formation separators 20XB and 20YB in the negative electrode inner peripheral portion 40T described above, the first heat-shrink part 26XT described above is applied to the first pre-formation separator 20XB and the second pre-formation separator 20YB is described above. The second heat contraction part 26YT thus formed is formed.

  Thereafter, the positive electrode current collecting member 91 is welded to the positive electrode lead portion 39 of the positive electrode plate 30 constituting the electrode body 10, and the negative electrode current collecting member 92 is welded to the negative electrode lead portion 49 of the negative electrode plate 40. And after accommodating the electrode body 10 in the battery case main body 81 and injecting the electrolyte solution 50, the battery case main body 81 was sealed with the sealing lid 82, and the battery 1 was completed (refer FIG. 4).

  The manufacturing method of the battery 1 according to the present embodiment includes the above-described electrode body manufacturing step and the lowered portion forming step. Therefore, the battery 1 in which at least one of the outer peripheral end surface 40SP and the inner peripheral end surface 40TP among the other end surface 40P of the negative electrode plate 40 is covered with the heat shrink portions 26XS, 26XT, 26YS, and 26YT of the separators 20X and 20Y. Can be manufactured. Accordingly, it is possible to suppress the elution of metal ions from the positive electrode active material particles of the positive electrode active material layer 31 at least in any one of the positive electrode outermost peripheral portion 30S and the positive electrode innermost peripheral portion 30T. The battery 1 in which the occurrence of a short circuit due to metal deposition on the material layer 41 is suppressed can be manufactured.

  Further, in the lowered portion forming step, among the pre-formation separators 20XB and 20YB wound around the electrode body 10, the protruding portions 26XB and 26YB protruding from the other side end face 40P to the other side DX2 are heated. The separator main body 20A is thermally contracted to form the thermal contraction portions 26XS, 26XT, 26YS, and 26YT. When the pre-formation separators 20XB and 20YB having the separator main body 20A and the heat-resistant layer 20B are heated, the separator main body 20A is largely heat-shrinked. 26XS, 26XT, 26YS, and 26YT can be easily formed.

In the above, the present invention has been described with reference to the embodiments (Examples 1 to 4). However, the present invention is not limited to the above-described embodiments, and can be appropriately modified and applied without departing from the gist thereof. Needless to say, you can.
For example, in the above-described embodiment, the liquid retention lowering portion of the separator is exemplified by a portion where the corresponding portion of the separator made of porous resin is thermally contracted by heating to lower the porosity than the interposition portion. However, as the liquid retention lowering part of the separator, in addition to this, the resin is applied to the corresponding part to lower the porosity than the intervening part, and the characteristic part repels without getting wet with the electrolyte solution Those provided with can also be used.
Furthermore, although the battery provided with the separator which has the separator main body which consists of porous resin, and a heat-resistant layer was shown in embodiment, the battery provided with the separator which consists only of a separator main body may be sufficient.

  Further, in the embodiment, as the lowered portion forming step, the protrusions 26XB and 26YB of the pre-formation separators 20XB and 20YB are heated and thermally contracted by using the two metal plates MB and MB, and the heat contracted portions 26XS and 26XT are formed. , 26YS, 26YT are exemplified. However, as the lowered portion forming step, for example, a heating device such as a heater is brought into contact with the end portion of the positive electrode lead portion (positive electrode foil) from the other side DX2 of the electrode body, and the positive electrode lead portion is heated from this end portion. And the method of forming the liquid-retention reduced portion by indirectly heating the protrusions of the separator located between the positive electrode lead portions by the positive electrode lead portion gradually heated from the other side DX2 and causing thermal contraction. It is done. In addition, a method of heating the positive electrode lead portion with the positive electrode lead portion sandwiched therebetween by a heating device such as a heater to indirectly heat the projecting portion and causing thermal contraction to form a liquid retention lowering portion is also mentioned. Further, in the case of forming a liquid retention reduced portion that covers the outer peripheral end face of the negative electrode outer peripheral portion, a heating device is brought into contact with the protruding portion of the separator from the radially outer side of the electrode body, and the protruding portion is heated and heated. A method of forming the liquid retention lowering portion by contraction is exemplified.

1 Battery (Lithium ion secondary battery)
10 Electrode body 20A Separator body 20AF Main body main surface (main surface of separator body)
20B Heat-resistant layer 20X First separator (separator)
20XB first pre-formation separator (separator not having a liquid retention reduction part)
20Y Second separator (separator)
20YB Second pre-formation separator (separator not having a liquid retention lowering portion)
22XT, 22XU, 22YS, 22YU Interposition part 26XB, 26YB Protrusion part 26XS, 26XT First heat contraction part (liquid retention lowering part)
26YS, 26YT second heat shrinkage part (liquid retention lowering part)
30 positive electrode plate 30S positive electrode outermost peripheral part 30T positive electrode innermost peripheral part 31 positive electrode active material layer 38 positive electrode foil 38F main surface 40 (negative electrode foil) main surface 40 negative electrode plate 40P other side end face 40S negative electrode outer peripheral part 40SP outer peripheral part end face 40T negative electrode inner peripheral part 40TP inner peripheral end face 40U negative electrode intermediate part 40UP intermediate end face 41 negative electrode active material layer 42, 42SH, 42TH facing part 44, 44SH, 44TH other side non-facing part 48 negative foil 48F (negative electrode foil) main surface 50 electrolyte AX Winding axis DR radial direction DR1 (radial) outer DR2 (radial) inner DX axial direction DX1 (axial) one side DX2 (axial) other side

Claims (4)

An electrode body formed by winding a belt-like positive electrode plate and a belt-like negative electrode plate through a belt-like separator, and an electrolyte impregnated in the separator,
The negative electrode plate is
Of the wound positive electrode plate, the positive electrode outermost peripheral portion positioned on the outermost periphery of the positive electrode, the negative electrode outer peripheral portion facing from the radially outer side through the separator, and the positive electrode outermost portion positioned on the innermost periphery of the positive electrode plate A lithium ion secondary battery having a negative electrode inner peripheral portion facing from the radially inner side through the separator on an inner peripheral portion,
The positive plate is
On both main surfaces of the strip-like positive electrode foil and the positive electrode foil, a positive electrode active material layer located on one side in the axial direction along the winding axis,
The negative electrode plate is
It has a negative electrode active material layer located on the other side in the axial direction on both main surfaces of the strip-shaped negative electrode foil and the negative electrode foil,
A negative electrode intermediate portion located between the negative electrode outer peripheral portion and the negative electrode inner peripheral portion;
The negative electrode foil and the two negative electrode active material layers form a common other side end face at the other side edge,
The negative electrode active material layer is
Including a facing portion that faces the positive electrode active material layer via the separator, and a non-facing portion on the other side that is adjacent to the other side of the facing portion and does not face the positive electrode active material layer,
The separator is
An interposition part interposed between the positive electrode active material layer and the facing part of the negative electrode active material layer opposite to the positive electrode active material layer, and a liquid retainability lowering part that lowers the electrolyte retention than the interposition part. And
Among the other end surface of the negative electrode plate, the inner peripheral end surface belonging to the outer peripheral end surface and the negative in-electrode peripheral portion belonging to the negative electrode outer peripheral portion,
Ri Na covered with the liquid-retaining property deterioration of the separator,
Of the other side end surfaces, the intermediate end surface belonging to the negative electrode intermediate portion is:
A lithium ion secondary battery exposed on the other side of the electrode body . The lithium ion secondary battery according to claim 1 ,
The separator is
A separator body made of porous resin;
Formed on one main surface of the separator body, and having a heat-resistant layer containing inorganic particles,
In the electrode body, the separator body is disposed in a form that is on the negative electrode active material layer side,
The liquid retention lowering part is
<br/> lithium ion secondary battery above Symbol separator body is a portion which is heat-shrinkable. An electrode body formed by winding a belt-like positive electrode plate and a belt-like negative electrode plate through a belt-like separator, and an electrolyte impregnated in the separator,
The negative electrode plate is
Of the wound positive electrode plate, the positive electrode outermost peripheral portion positioned on the outermost periphery of the positive electrode, the negative electrode outer peripheral portion facing from the radially outer side through the separator, and the positive electrode outermost portion positioned on the innermost periphery of the positive electrode plate An inner peripheral portion having a negative electrode inner peripheral portion facing from the radially inner side via the separator,
The positive plate is
On both main surfaces of the strip-like positive electrode foil and the positive electrode foil, a positive electrode active material layer located on one side in the axial direction along the winding axis,
The negative electrode plate is
It has a negative electrode active material layer located on the other side in the axial direction on both main surfaces of the strip-shaped negative electrode foil and the negative electrode foil,
A negative electrode intermediate portion located between the negative electrode outer peripheral portion and the negative electrode inner peripheral portion;
The negative electrode foil and the two negative electrode active material layers form a common other side end face at the other side edge,
The negative electrode active material layer is
Including a facing portion that faces the positive electrode active material layer via the separator, and a non-facing portion on the other side that is adjacent to the other side of the facing portion and does not face the positive electrode active material layer,
The separator is
An interposition part interposed between the positive electrode active material layer and the facing part of the negative electrode active material layer opposite to the positive electrode active material layer, and a liquid retainability lowering part that lowers the electrolyte retention than the interposition part. And
Among the other end surface of the negative electrode plate, the inner peripheral end surface belonging to the outer peripheral end surface and the negative in-electrode peripheral portion belonging to the negative electrode outer peripheral portion,
Ri Na covered with the liquid-retaining property deterioration of the separator,
Of the other side end surfaces, the intermediate end surface belonging to the negative electrode intermediate portion is:
A method of manufacturing a lithium ion secondary battery, which is exposed on the other side of the electrode body ,
An electrode body production step of producing an electrode body by winding the belt-like positive electrode plate and the belt-like negative electrode plate through a belt-like separator having no liquid retention lowering portion;
The manufacturing method of a lithium ion secondary battery provided with the reduced part formation process which forms the said liquid retention reduced part in the said separator wound by making the said electrode body. It is a manufacturing method of the lithium ion secondary battery according to claim 3 ,
The separator is
A separator body made of porous resin;
Formed on one main surface of the separator body, and having a heat-resistant layer containing inorganic particles,
In the electrode body, the separator body is disposed in a form that is on the negative electrode active material layer side,
The liquid retention lowering portion is formed by thermally shrinking the separator body by heating,
The lowered portion forming step includes
Of the separator that does not have the liquid retainability lowered portion wound around the electrode body, the protruding portion protruding to the other side of the other side end surface is heated, and the separator main body is thermally contracted. The manufacturing method of the lithium ion secondary battery which forms the said liquid retainability fall part.

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