Battery

Abstract

High-rate degradation is suppressed by reducing the difference between the amount of electrolyte moved between the outer electrode body and the positive electrode sheet and the amount of electrolyte moved between the outer electrode body and the negative electrode sheet when the battery is charging and discharging. [Solution] A battery having a wound body formed by winding a laminate 65 having a long strip-shaped negative electrode sheet 40, a long strip-shaped positive electrode sheet 50, and a plurality of long strip-shaped separators 60A, 60B located between the negative electrode sheet and the positive electrode sheet and stretched in a predetermined stretching direction, around a virtual axis extending in the width direction of the laminate, wherein the wound body is impregnated with an electrolyte, and the separators include a positive electrode opposing separator 60A that faces the positive electrode sheet and whose stretching direction is parallel to the winding direction of the laminate, and a negative electrode opposing separator 60B that faces the negative electrode sheet and whose stretching direction is parallel to the width direction G.

Description

Technical Field

[0001] The present invention relates to a battery.

Background Art

[0002] Patent Document 1 below discloses a battery including a wound electrode body. This electrode body includes a long strip-shaped positive electrode, a long strip-shaped negative electrode, and a long strip-shaped separator positioned between the positive electrode and the negative electrode. The separator includes a base material layer and a particle layer provided on the positive electrode side surface of the base material layer. Further, the particle layer is provided with a diffusion path extending along the width direction of the separator (electrode body). Therefore, when the battery is charged and discharged, the electrolyte of the electrode body is easily discharged to the outside of the electrode body through the diffusion path, and the electrolyte outside the electrode body is easily returned to the electrode body through the diffusion path. Therefore, the battery of Patent Document 1 can suppress the occurrence of uneven salt concentration in the electrode body as compared with the case where the separator is not provided with a diffusion path.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1 above, the movement of the electrolyte through the separator between the outside of the electrode body and the positive electrode when the battery is charged and discharged becomes smoother as compared with the case where the separator is not provided with a diffusion path. However, usually, the amount of movement of the electrolyte that does not pass through the separator between the outside of the electrode body and the negative electrode when the battery is charged and discharged is larger than the amount of movement of the electrolyte that does not pass through the separator between the outside of the electrode body and the positive electrode. Therefore, it is difficult to reduce the difference between the amount of movement of the electrolyte between the outside of the electrode body and the positive electrode and the amount of movement of the electrolyte between the outside of the electrode body and the negative electrode when the battery is charged and discharged. Therefore, the battery of Patent Document 1 has room for improvement in suppressing high-rate deterioration.

[0005] Considering the above facts, the present invention aims to provide a battery capable of suppressing high-rate degradation by reducing the difference between the amount of electrolyte movement between the outside of the electrode body and the positive electrode sheet and the amount of electrolyte movement between the outside of the electrode body and the negative electrode sheet when the battery is charging and discharging. [Means for solving the problem]

[0006] A battery according to a first aspect of the present invention has a wound body formed by winding a laminate having a long strip-shaped negative electrode sheet, a long strip-shaped positive electrode sheet, and a plurality of long strip-shaped separators located between the negative electrode sheet and the positive electrode sheet and stretched in a predetermined stretching direction, around a virtual axis extending in the width direction of the laminate, wherein the wound body is impregnated with an electrolyte, and the separators include a positive electrode opposing separator facing the positive electrode sheet and having a stretching direction parallel to the winding direction of the laminate, and a negative electrode opposing separator facing the negative electrode sheet and having a stretching direction parallel to the width direction.

[0007] In the battery according to the second aspect of the present invention, the sum of the volumes of all holes formed in the positive electrode opposing separator is greater than the sum of the volumes of all holes formed in the negative electrode opposing separator.

[0008] In a third aspect of the present invention, the thickness of the positive electrode opposing separator is greater than the thickness of the negative electrode opposing separator.

[0009] In the battery according to the fourth aspect of the present invention, the porosity, which is the sum of the area of ​​the holes per unit cross-sectional area of ​​the separator, is greater for the positive electrode opposing separator than for the negative electrode opposing separator. [Effects of the Invention]

[0010] When the battery of the first embodiment of the present invention is charged and discharged, the positive electrode opposing separator, whose stretching direction is parallel to the winding direction of the laminate, discharges electrolyte to the outside of the electrode body more easily than the negative electrode opposing separator, whose stretching direction is parallel to the width direction of the laminate. Therefore, the amount of electrolyte that moves between the outside of the electrode body and the positive electrode sheet via the positive electrode opposing separator when the battery is charged and discharged can be made larger than the amount of electrolyte that moves between the outside of the electrode body and the negative electrode sheet via the negative electrode opposing separator. Consequently, although the amount of electrolyte that moves between the outside of the electrode body and the negative electrode sheet without the negative electrode opposing separator is greater than the amount of electrolyte that moves between the outside of the electrode body and the positive electrode sheet without the positive electrode opposing separator, when considering the battery as a whole, the difference between the amount of electrolyte that moves between the outside of the electrode body and the positive electrode sheet and the amount of electrolyte that moves between the outside of the electrode body and the negative electrode sheet when charging and discharge is reduced. Therefore, high-rate degradation of the battery of the first embodiment is suppressed.

[0011] According to the battery of the second aspect of the present invention, when the battery is charging or discharging, the positive electrode opposing separator makes it easier to discharge the electrolyte to the outside of the electrode body.

[0012] According to the battery of the third aspect of the present invention, it is possible to promote the discharge of electrolyte to the outside of the electrode body by the positive electrode opposing separator when the battery is charging or discharging, while suppressing a decrease in the mechanical strength of the positive electrode opposing separator.

[0013] According to the fourth aspect of the present invention, the discharge of electrolyte to the outside of the electrode body by the positive electrode opposing separator when the battery is charging or discharging can be promoted without increasing the thickness of the positive electrode opposing separator. Therefore, a decrease in the amount (thickness) of active material provided on the negative electrode sheet and the positive electrode sheet can be suppressed. [Brief explanation of the drawing]

[0014] [Figure 1] This is a front view showing a lithium-ion secondary battery according to an embodiment. [Figure 2] This is a disassembled perspective view of a lithium-ion secondary battery according to an embodiment. [Figure 3]Exploded perspective view of the positive electrode sheet, positive electrode facing separator, negative electrode facing separator, and negative electrode sheet. [Figure 4] Cross-sectional view taken along a plane perpendicular to the longitudinal direction of the laminate of the positive electrode sheet, positive electrode facing separator, negative electrode facing separator, and negative electrode sheet. [Figure 5] Perspective view showing the wound body cut along the arrow 5-5 in FIG. 2. [Figure 6] Graph showing the relationship between the stretching direction of the separator and the amount of non-aqueous electrolyte discharged per unit time from the separator. [Figure 7] Cross-sectional view taken along a plane perpendicular to the longitudinal direction of the laminate of the positive electrode facing separator and negative electrode facing separator of the modified example. [Embodiments for Carrying Out the Invention]

[0015] Hereinafter, the battery according to the embodiment will be described with reference to FIGS. 1 to 6. The battery according to the embodiment is, for example, a lithium-ion secondary battery as a cell battery that constitutes a battery module used as an in-vehicle power source for an electric vehicle (BEV: Battery Electric Vehicle), a hybrid vehicle (HEV: Hybrid Electric Vehicle), or a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle). In each figure, arrow D indicates the longitudinal direction of the lithium-ion secondary battery 10 (hereinafter referred to as the battery 10), arrow E indicates the depth direction of the battery 10, and arrow F indicates the vertical direction of the battery 10.

[0016] [Configuration of Battery 10] As shown in FIGS. 1 and 2, the battery 10 has a lid assembly 20, a wound body (electrode body) 30, and a battery case 70.

[0017] (Battery Case 70) The battery case 70 is made of, for example, aluminum and has a rectangular parallelepiped shape with an open top surface.

[0018] (Cover Assembly 20) The cover assembly 20 includes a cover member 21, a negative current collector terminal 22 as a current collector terminal, a positive current collector terminal 23 as a current collector terminal, a negative external terminal 24 as an external terminal, and a positive external terminal 25 as an external terminal.

[0019] <Cover Member 21> The cover member 21 is, for example, made of aluminum and is a plate-like member extending in the longitudinal direction D. The cover member 21 is provided with a safety valve 21A and a cap 26 for closing the injection port 21B.

[0020] The safety valve 21A opens when the value of the internal pressure of the battery case 70 reaches a predetermined pressure, and discharges the gas generated inside the battery case 70.

[0021] The injection port 21B is a through hole penetrating the cover member 21 in the vertical direction. The injection port 21B is used when injecting a non-aqueous electrolyte (electrolyte, not shown) into the battery case 70. A cap 26 is attached to the injection port 21B in an airtight and liquid-tight state, for example, by laser welding.

[0022] <Negative Current Collector Terminal 22 and Negative External Terminal 24> The negative current collector terminal 22 and the negative external terminal 24 are formed of, for example, copper and are provided at the other end of the cover member 21 in the longitudinal direction D. The negative current collector terminal 22 is a rectangular plate-like member with the depth direction E as the plate thickness direction. The negative external terminal 24 is electrically connected to the negative current collector terminal 22 and is exposed outside the cover member 21.

[0023] <Positive Current Collector Terminal 23 and Positive External Terminal 25> The positive current collector terminal 23 and the positive external terminal 25 are formed of, for example, aluminum and are provided at one end of the cover member 21 in the longitudinal direction D. The positive current collector terminal 23 is a rectangular plate-like member with the depth direction E as the plate thickness direction. The positive external terminal 25 is electrically connected to the positive current collector terminal 23 and is exposed outside the cover member 21.

[0024] (Wound Body 30) As shown in Figures 2 and 5, the winding body 30 includes a power generator 31, a negative electrode current collector 46, and a positive electrode current collector 54.

[0025] As shown in Figures 3 to 5, the wound body 30 is composed of a laminate 65 having a long strip-shaped negative electrode sheet 40 as an electrode sheet, a long strip-shaped positive electrode sheet 50 as an electrode sheet, a long strip-shaped positive electrode opposing separator (separator) 60A, and a long strip-shaped negative electrode opposing separator (separator) 60B. The laminate 65 comprises two positive electrode opposing separators 60A and two negative electrode opposing separators 60B. The negative electrode sheet 40, positive electrode sheet 50, positive electrode opposing separator 60A, and negative electrode opposing separator 60B are flexible. As shown in Figure 5, the wound body 30 is constructed by winding the laminate 65 around a virtual axis IAX that extends in the width direction G of the negative electrode sheet 40, positive electrode sheet 50, positive electrode opposing separator 60A, and negative electrode opposing separator 60B. As shown in Figures 2 and 5, the coiled body 30 has a flattened shape.

[0026] <Negative electrode sheet 40> As shown in Figure 3, the negative electrode sheet 40 comprises a long, strip-shaped negative electrode body 41, a first negative electrode active material 42 coated on one side of the negative electrode body 41, and a second negative electrode active material 43 coated on the other side of the negative electrode body 41. The negative electrode body 41 is made of, for example, copper foil. The first negative electrode active material 42 and the second negative electrode active material 43 contain graphite. The first negative electrode active material 42 and the second negative electrode active material 43 are porous members having a large number of pores, and have an inner circumferential negative electrode active material which is the part on the negative electrode body 41 side, and an outer circumferential negative electrode active material which is the part on the opposite side of the negative electrode body 41. As shown in Figure 3, the first negative electrode active material 42 and the second negative electrode active material 43 are coated only on the areas of both sides of the negative electrode body 41, excluding the other side in the width direction G. Therefore, a negative electrode current collector portion 46 is formed on the other side of the negative electrode body 41 in the width direction G, where the first negative electrode active material 42 and the second negative electrode active material 43 are not coated.

[0027] <Positive electrode sheet 50> As shown in Figure 3, the positive electrode sheet 50 comprises a long, strip-shaped positive electrode body 51, a first positive electrode active material 52 coated on one side of the positive electrode body 51, and a second positive electrode active material 53 coated on the other side of the positive electrode body 51. The first positive electrode active material 52 and the second positive electrode active material 53 are porous members having numerous pores, and have an inner circumferential positive electrode active material on the side facing the positive electrode body 51, and an outer circumferential positive electrode active material on the side opposite to the positive electrode body 51. The positive electrode body 51 is made of, for example, aluminum foil. As shown in Figure 3, the first positive electrode active material 52 and the second positive electrode active material 53 are coated only on the regions of both sides of the positive electrode body 51, excluding one side in the width direction G. Therefore, a positive electrode current collector portion 54 is formed on one side of the positive electrode body 51 in the width direction G where the first positive electrode active material 52 and the second positive electrode active material 53 are not coated.

[0028] <Positive electrode opposing separator 60A, negative electrode opposing separator 60B> The positive electrode opposing separator 60A and the negative electrode opposing separator 60B are long, strip-shaped members that electrically insulate the negative electrode sheet 40 and the positive electrode sheet 50, and allow the movement of charge carriers between the negative electrode sheet 40 and the positive electrode sheet 50. The positive electrode opposing separator 60A and the negative electrode opposing separator 60B are composed of microporous sheets having numerous pores. The positive electrode opposing separator 60A and the negative electrode opposing separator 60B are manufactured by stretching a plasticizer-added film, which has been made dry or wet, in a predetermined direction to form fine voids (pores) through which the electrolyte can pass.

[0029] The positive electrode opposing separator 60A is stretched along its longitudinal direction LD (see Figure 3) during manufacturing. On the other hand, the negative electrode opposing separator 60B is stretched along its width direction G (see Figure 3) during manufacturing. That is, the direction of stretching of the positive electrode opposing separator 60A and the direction of stretching of the negative electrode opposing separator 60B are orthogonal to each other.

[0030] Furthermore, as shown in Figure 4, the thickness TA of the positive electrode opposing separator 60A is greater than the thickness TB of the negative electrode opposing separator 60B. The dimensions are substantially the same. Therefore, the cross-sectional area AA of the positive electrode opposing separator 60A is greater than the cross-sectional area AB of the negative electrode opposing separator 60B. The positive electrode opposing separator 60A has numerous holes 62 formed in the width direction G of the positive electrode opposing separator 60A and the width direction G of the negative electrode opposing separator 60B, and the negative electrode opposing separator 60B has numerous holes 63 formed in it. As shown in Figure 4, the sum of the areas of all holes 62 per unit area (unit cross-sectional area) of the cross section perpendicular to the longitudinal direction LD of the positive electrode opposing separator 60A and the sum of the areas of all holes 63 per unit cross-sectional area of ​​the negative electrode opposing separator 60B are substantially the same. That is, the void ratio in the positive electrode opposing separator 60A and the void ratio in the negative electrode opposing separator 60B are substantially the same. The porosity can be measured, for example, by the Archimedes method. However, as mentioned above, since the cross-sectional area AA of the positive electrode opposing separator 60A is larger than the cross-sectional area AB of the negative electrode opposing separator 60B, the sum of the volumes of all the holes 62 formed in the positive electrode opposing separator 60A is greater than the sum of the volumes of all the holes 63 formed in the negative electrode opposing separator 60B.

[0031] As shown in Figures 3 and 4, the wound body 30 has two separator sets in which a positive electrode opposing separator 60A and a negative electrode opposing separator 60B are in contact with each other. One side of the negative electrode opposing separator 60B of one separator set faces the first negative electrode active material 42 of the negative electrode sheet 40. One side of the positive electrode opposing separator 60A of the other separator set faces the first positive electrode active material 52 of the positive electrode sheet 50. Furthermore, one side of the negative electrode opposing separator 60B of the other separator set faces the second negative electrode active material 43 of the negative electrode sheet 40. One side of the positive electrode opposing separator 60A of the other separator set faces the second positive electrode active material 53 of the positive electrode sheet 50. Furthermore, in each separator set, the other side of the positive electrode opposing separator 60A faces the other side of the negative electrode opposing separator 60B. That is, as shown in Figure 4, the positive electrode opposing separator 60A, the negative electrode opposing separator 60B, the negative electrode sheet 40, the negative electrode opposing separator 60B, the positive electrode opposing separator 60A, and the positive electrode sheet 50 are stacked in this order, and the laminate 65 is composed of one negative electrode sheet 40, two negative electrode opposing separators 60B, two positive electrode opposing separators 60A, and one positive electrode sheet 50. As shown in Figure 4, one end of the positive electrode current collector 54 of the positive electrode body 51 in the width direction G is located on one side of the positive electrode opposing separator 60A and the negative electrode opposing separator 60B. The other end of the negative electrode current collector portion 46 of the negative electrode body 41 in the width direction G is located on the other side of the width direction G from the positive electrode opposing separator 60A and the negative electrode opposing separator 60B.

[0032] The laminate 65 is wound around a virtual axis IAX extending in the width direction G to form the wound body 30 shown in Figures 2 and 5. The positive electrode current collector 54 is wound to form one end of the wound body 30 in the width direction G, and the negative electrode current collector 46 is wound to form the other end of the wound body 30 in the width direction G. Furthermore, the region between the negative electrode current collector 46 and the positive electrode current collector 54 of the wound body 30 is the power generator 31. The power generator 31 has the function of storing electrical energy from the battery 10.

[0033] The lower end of the negative electrode current collector terminal 22 is connected to the vertical center of the negative electrode current collector section 46 of the wound body 30 by ultrasonic welding, and the lower end of the positive electrode current collector terminal 23 is connected to the vertical center of the positive electrode current collector section 54 by resistance welding. Furthermore, the negative electrode current collector terminal 22, the positive electrode current collector terminal 23, and the wound body 30 are housed as a single unit in the internal space of the battery case 70, which is filled with a non-aqueous electrolyte. Finally, the lid member 21 is fixed to the upper end of the battery case 70 by laser welding, completing the battery 10 shown in Figure 1. The upper end opening of the battery case 70 is sealed in an airtight and liquid-tight state by the lid member 21.

[0034] Once the battery 10 is completed in this way, the non-aqueous electrolyte is impregnated into the numerous pores of the first negative electrode active material 42 and the second negative electrode active material 43, as well as the numerous pores of the first positive electrode active material 52 and the second positive electrode active material 53, within the battery case 70. Furthermore, the non-aqueous electrolyte is impregnated into the numerous holes 62 of the positive electrode opposing separator 60A and the numerous holes 63 of the negative electrode opposing separator 60B.

[0035] [Effects of Battery 10] When the battery 10 performs charging and discharging, the negative electrode sheet 40 and the positive electrode sheet 50 repeatedly expand and contract. The negative electrode deformation, which is the change in shape between the expanded and contracted shapes of the negative electrode sheet 40, is greater than the positive electrode deformation, which is the change in shape between the expanded and contracted shapes of the positive electrode sheet 50. Furthermore, due to this expansion and contraction, the non-aqueous electrolyte present in the pores of the negative electrode sheet 40 and the positive electrode sheet 50 during charging and discharging is discharged to the outside of the winding body 30 from both end faces in the width direction G of the negative electrode sheet 40 and the positive electrode sheet 50. Also, during charging and discharging, due to the contraction of the negative electrode sheet 40 and the positive electrode sheet 50, the non-aqueous electrolyte on the outside of the winding body 30 tries to return to the inside of the negative electrode sheet 40 and the positive electrode sheet 50 from both end faces in the width direction G of the negative electrode sheet 40 and the positive electrode sheet 50. Furthermore, because the amount of deformation of the negative electrode is greater than the amount of deformation of the positive electrode, the amount of non-aqueous electrolyte discharged per unit time from both end faces in the width direction G of the negative electrode sheet 40 without passing through the negative electrode opposing separator 60B during charging and discharging is greater than the amount of non-aqueous electrolyte discharged per unit time from both end faces in the width direction G of the positive electrode sheet 50 without passing through the positive electrode opposing separator 60A. Also, the amount of non-aqueous electrolyte returning per unit time from the outside of the wound body 30 to the negative electrode sheet 40 without passing through the negative electrode opposing separator 60B during charging and discharging is greater than the amount of non-aqueous electrolyte returning per unit time from the outside of the wound body 30 to the positive electrode sheet 50 without passing through the positive electrode opposing separator 60A.

[0036] However, in this embodiment, the extension direction of the positive electrode opposing separator 60A is parallel to its longitudinal direction LD, and the extension direction of the negative electrode opposing separator 60B is parallel to its width direction G. Figure 6 is a graph showing the relationship between the amount of non-aqueous electrolyte discharged per unit time from a predetermined separator to the outside and the extension direction of the separator. Here, MD is the extension direction, and TD is the direction perpendicular to the extension direction. As is clear from this graph, the amount of non-aqueous electrolyte discharged per unit time from both end faces in the width direction of the separator is greater in the perpendicular direction TD than in the extension direction MD. In other words, when the battery 10 is charging and discharging, the amount of non-aqueous electrolyte discharged per unit time from both end faces in the width direction G of the positive electrode opposing separator 60A, whose stretching direction is parallel to the longitudinal direction LD of the laminate 65 (winding direction of the laminate 65), to the outside of the wound body 30 tends to be greater than that of the negative electrode opposing separator 60B, whose stretching direction is parallel to the width direction G of the laminate 65. Furthermore, the amount of non-aqueous electrolyte returning per unit time from the outside of the laminate 65 to each separator also tends to be greater for the positive electrode opposing separator 60A than for the negative electrode opposing separator 60B.

[0037] Furthermore, as described above, the sum of the volumes of all the holes 62 formed in the positive electrode opposing separator 60A is greater than the sum of the volumes of all the holes 63 formed in the negative electrode opposing separator 60B. Therefore, compared to the case where the sum of the volumes of all the holes 62 formed in the positive electrode opposing separator 60A is less than or equal to the sum of the volumes of all the holes 63 formed in the negative electrode opposing separator 60B, the amount of non-aqueous electrolyte discharged per unit time from both end faces in the width direction G of the positive electrode opposing separator 60A to the outside of the wound body 30 tends to be greater than that of the negative electrode opposing separator 60B.

[0038] Therefore, the amount of non-aqueous electrolyte moving per unit time between the outside of the wound body 30 and the positive electrode sheet 50 via the positive electrode opposing separator 60A when the battery 10 is charging and discharging can be made larger than the amount of non-aqueous electrolyte moving per unit time between the outside of the wound body 30 and the negative electrode sheet 40 via the negative electrode opposing separator 60B. Consequently, although the amount of non-aqueous electrolyte moving per unit time between the outside of the wound body 30 and the negative electrode sheet 40 without the negative electrode opposing separator 60B is greater than the amount of non-aqueous electrolyte moving per unit time between the outside of the wound body 30 and the positive electrode sheet 50 without the positive electrode opposing separator 60A, when considering the battery 10 as a whole, the difference between the amount of non-aqueous electrolyte (electrolyte) moving between the outside of the wound body 30 and the positive electrode sheet 50 and the amount of non-aqueous electrolyte (electrolyte) moving between the outside of the wound body 30 and the negative electrode sheet 40 when charging and discharging is performed becomes smaller. Therefore, when the battery 10 is charged and discharged at a high rate, unevenness in the lithium salt concentration of the non-aqueous electrolyte in the wound body 30 is less likely to occur, and thus the high-rate resistance is less likely to increase. As a result, high-rate degradation of the battery 10 is suppressed.

[0039] Furthermore, although the total volume of all holes 62 formed in the positive electrode opposing separator 60A is greater than the total volume of all holes 63 formed in the negative electrode opposing separator 60B, the thickness TA of the positive electrode opposing separator 60A is greater than the thickness TB of the negative electrode opposing separator 60B. Therefore, a decrease in the mechanical strength of the positive electrode opposing separator 60A can be suppressed.

[0040] Although a battery according to an embodiment has been described above, the battery can be modified in design as appropriate without departing from the spirit of the present invention.

[0041] For example, the battery 10 may be implemented in the modified form shown in Figure 7. The thickness TA of the positive electrode opposing separator 60A of this battery 10 is substantially the same as the thickness TB of the negative electrode opposing separator 60B, and the widthwise dimension G of the positive electrode opposing separator 60A and the widthwise dimension G of the negative electrode opposing separator 60B are substantially the same. On the other hand, the porosity of the positive electrode opposing separator 60A is greater than that of the negative electrode opposing separator 60B. Therefore, compared to the case where the porosity of the positive electrode opposing separator 60A is less than or equal to that of the negative electrode opposing separator 60B, the amount of non-aqueous electrolyte per unit time that moves between the outside of the wound body 30 and the positive electrode sheet 50 via the positive electrode opposing separator 60A when the battery 10 is charging and discharging is likely to be greater than the amount of non-aqueous electrolyte per unit time that moves between the outside of the wound body 30 and the negative electrode sheet 40 via the negative electrode opposing separator 60B. Therefore, high-rate degradation is suppressed even in the modified battery 10.

[0042] Furthermore, in this modified battery 10, the thickness TA of the positive electrode opposing separator 60A of the battery 10 is not greater than the thickness TB of the negative electrode opposing separator 60B. In this way, without increasing the thickness of the positive electrode opposing separator 60A, the discharge of non-aqueous electrolyte to the outside of the wound body 30 by the positive electrode opposing separator 60A when the battery 10 is charging or discharging can be promoted. Therefore, a decrease in the amount (thickness) of the active materials 42, 43, 52, and 53 provided on the negative electrode sheet 40 and the positive electrode sheet 50 can be suppressed.

[0043] Furthermore, if the thickness TA of the positive electrode opposing separator 60A is greater than or less than the thickness TB of the negative electrode opposing separator 60B, the porosity of the positive electrode opposing separator 60A may be made greater than that of the negative electrode opposing separator 60B, so that the total volume of all holes 62 formed in the positive electrode opposing separator 60A is greater than the total volume of all holes 63 formed in the negative electrode opposing separator 60B. [Explanation of symbols]

[0044] 10. Lithium-ion rechargeable battery (battery) 30 Wound body (electrode body) 40 Negative Electrode Sheets 50 Positive Electrode Sheets 60A Positive Electrode Opposing Separator (Separator) 60B Negative Electrode Opposing Separator (Separator) 62 holes 63 holes 65 Laminate G Width direction TA thickness TB thickness IAX virtual axis MD stretching direction

Claims

1. A battery having a wound body formed by winding a laminate, which has a long strip-shaped negative electrode sheet, a long strip-shaped positive electrode sheet, and a plurality of long strip-shaped separators located between the negative electrode sheet and the positive electrode sheet and stretched in a predetermined stretching direction, around a virtual axis extending in the width direction of the laminate, The aforementioned wound body is impregnated with an electrolyte solution, The aforementioned separator, A positive electrode opposing separator facing the positive electrode sheet and having an extension direction parallel to the winding direction of the laminate, A negative electrode opposing separator facing the negative electrode sheet and having an extension direction parallel to the width direction, A battery equipped with these features.

2. The battery according to claim 1, wherein the total volume of all holes formed in the positive electrode opposing separator is greater than the total volume of all holes formed in the negative electrode opposing separator.

3. The battery according to claim 2, wherein the thickness of the positive electrode opposing separator is greater than the thickness of the negative electrode opposing separator.

4. The battery according to claim 2 or 3, wherein the porosity, which is the sum of the area of ​​the holes per unit cross-sectional area of ​​the separator, is greater for the positive electrode opposing separator than for the negative electrode opposing separator.

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