Battery

Abstract

To suppress high-rate deterioration and thermal shrinkage of a separator.SOLUTION: A battery has a wound body 30 obtained by winding a laminate having a long strip-shaped negative electrode sheet 40, a long strip-shaped positive electrode sheet 50, and long strip-shaped separators 60A, 60B located between the negative electrode sheet and the positive electrode sheet, around a virtual axis extending in a width direction G of the laminate, wherein an amount of change between a shape of the negative electrode sheet when expanded and a shape of the negative electrode sheet when contracted is greater than an amount of change between a shape of the positive electrode sheet when expanded and a shape of the positive electrode sheet when contracted, and the separator includes: a long strip-shaped base material layer 61; a plurality of first coating layers 63 provided on a surface of the base material layer facing the negative electrode sheet, extending along a longitudinal direction of the separator, spaced apart from each other in the width direction, and having a porosity different from that of the base material layer; and a plurality of second coating layers 66 provided on a surface of the base material layer facing the positive electrode sheet, extending along the width direction, spaced apart from each other in the longitudinal direction, and having a porosity different from that of the base material layer.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a battery. [Background technology]

[0002] The following Patent Document 1 discloses a battery including a wound-type electrode body. This electrode body includes a long strip-shaped positive electrode, a long strip-shaped negative electrode, and a long strip-shaped separator located between the positive electrode and the negative electrode. The separator includes a base layer and a particle layer provided on the surface of the base layer on the positive electrode side. Furthermore, 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 compared to a case where the separator does not have a diffusion path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-68504 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above Patent Document 1, the amount of electrolyte moving between the outside of the electrode body and the positive electrode through the separator when the battery is charged and discharged is smoother than when the separator is not provided with a diffusion path. However, usually, the amount of electrolyte moving between the outside of the electrode body and the negative electrode without the separator when the battery is charged and discharged is larger than the amount of electrolyte moving between the outside of the electrode body and the positive electrode without the separator. Therefore, it is difficult to reduce the difference between the amount of electrolyte moving between the outside of the electrode body and the positive electrode and the amount of electrolyte moving between the outside of the electrode body and the negative electrode when the battery is charged and discharged. Therefore, the battery of the above Patent Document 1 has room for improvement in terms of suppressing high-rate degradation.

[0005] Furthermore, the particle layer of the separator in Patent Document 1 is provided only on one surface of the substrate layer, making it difficult for the invention in Patent Document 1 to suppress thermal shrinkage of the separator.

[0006] In consideration of the above, an object of the present invention is to provide a battery capable of suppressing high-rate deterioration and thermal shrinkage of a separator. [Means for solving the problem]

[0007] A first aspect of the battery of the present invention includes a laminate having a long strip-shaped negative electrode sheet, a long strip-shaped positive electrode sheet, and a long strip-shaped separator located between the negative electrode sheet and the positive electrode sheet, the laminate being wound around a virtual axis extending in the width direction of the laminate, and the positive electrode sheet and the positive electrode sheet expand and contract due to charging and discharging, and an amount of change between the shape of the negative electrode sheet when expanded and the shape of the negative electrode sheet when contracted is larger than an amount of change between the shape of the positive electrode sheet when expanded and the shape of the positive electrode sheet when contracted, and the separator includes a long strip-shaped base layer, a plurality of first coating layers provided on a surface of the base layer facing the negative electrode sheet, extending along the longitudinal direction of the separator and spaced apart from each other in the width direction, the first coating layers having a porosity different from that of the base layer, and a plurality of second coating layers provided on the surface of the base layer facing the positive electrode sheet, extending along the width direction, spaced apart from each other in the longitudinal direction, the second coating layers having a porosity different from that of the base layer.

[0008] In the battery according to the second aspect of the present invention, the second coating layer has a larger porosity than the base layer, and the second coating layer is provided over the entire base layer in the width direction. Effect of the Invention

[0009] In the battery according to the first aspect of the present invention, the positive electrode sheet and the negative electrode sheet expand and contract due to charge and discharge, and the amount of change between the shape of the negative electrode sheet during expansion and the shape during contraction is larger than the amount of change between the shape of the positive electrode sheet during expansion and the shape during contraction. In the battery of the first aspect, the separator includes a long strip-shaped base material layer, a plurality of first coat layers provided on the surface of the base material layer facing the negative electrode sheet and having a porosity different from that of the base material layer, and a plurality of second coat layers provided on the surface of the base material layer facing the positive electrode sheet and having a porosity different from that of the base material layer. Further, the first coat layer extends along the longitudinal direction of the separator (laminate), while the second coat layer extends along the width direction of the separator. Therefore, when the battery is charged and discharged, the movement of the electrolyte through the separator between the outside of the electrode body and the negative electrode sheet occurs along a portion where the first coat layer is not formed in the first coat layer or the base material layer and the porosity is large. That is, the movement of the electrolyte along the longitudinal direction of the separator is promoted. Thereby, the movement of the electrolyte in the width direction of the separator is suppressed, and the amount of movement of the electrolyte between the outside of the electrode body and the negative electrode sheet is suppressed. On the other hand, when the battery is charged and discharged, the movement of the electrolyte through the separator between the outside of the electrode body and the positive electrode sheet occurs along a portion where the second coat layer is not formed in the second coat layer or the base material layer and the porosity is large. That is, the movement of the electrolyte along the width direction of the separator is promoted. Thereby, the movement of the electrolyte in the longitudinal direction of the separator is suppressed, and the amount of movement of the electrolyte between the outside of the electrode body and the positive electrode sheet is promoted. Therefore, the amount of movement of the electrolyte through the separator between the outside of the electrode body and the positive electrode sheet when the battery is charged and discharged can be made larger than the amount of movement of the electrolyte through the separator between the outside of the electrode body and the negative electrode sheet. Therefore, the battery of the first aspect can reduce the difference between the amount of movement of the electrolyte between the outside of the electrode body and the positive electrode sheet and the amount of movement of the electrolyte between the outside of the electrode body and the negative electrode sheet when charging and discharging. Therefore, the battery of the first aspect can suppress high-rate deterioration.

[0010] Furthermore, the extension directions of the first coat layer and the second coat layer of the separator of the battery according to the first embodiment of the present invention are perpendicular to each other, so that the battery according to the first embodiment of the present invention is easier to suppress thermal shrinkage of the separator than when the separator has only one of the first coat layer and the second coat layer.

[0011] According to the battery of the second aspect of the present invention, the movement of the electrolyte via the separator between the outside of the electrode assembly and the positive electrode sheet when the battery is charged and discharged can be more easily promoted. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a front view showing a lithium-ion secondary battery according to an embodiment. [Diagram 2] FIG. 1 is an exploded perspective view of a lithium-ion secondary battery according to an embodiment. [Diagram 3] FIG. 2 is an exploded perspective view of a positive electrode sheet, a separator, and a negative electrode sheet. [Figure 4] 2 is a cross-sectional view taken along a plane perpendicular to the longitudinal direction of a laminate of a positive electrode sheet, a separator, and a negative electrode sheet. FIG. [Diagram 5] 5 is a perspective view showing the wound body cut along the arrow line 5-5 in FIG. 2. [Figure 6] FIG. 2 is a perspective view of a wound body showing a positive electrode sheet, a separator, and a part of a negative electrode sheet in an unwound state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a battery according to an embodiment will be described with reference to the drawings. The battery according to the embodiment is, for example, a lithium-ion secondary battery serving as a cell battery constituting a battery module used as an on-board power source for electric vehicles, hybrid vehicles, etc. In each drawing, arrow D indicates the longitudinal direction of the lithium-ion secondary battery (battery) 10, arrow E indicates the depth direction of the lithium-ion secondary battery 10, and arrow F indicates the up-down direction of the lithium-ion secondary battery 10.

[0014] [Configuration of lithium-ion secondary battery 10] As shown in FIGS. 1 and 2, the lithium ion secondary battery 10 includes a lid assembly 20, a wound body (electrode body) 30, and a battery case 70.

[0015] (battery case 70) The battery case 70 is made of, for example, aluminum, and has a rectangular parallelepiped shape with an open top.

[0016] (Lid Assembly 20) The lid assembly 20 includes a lid member 21, a negative electrode current collector terminal 22 as a current collector terminal, a positive electrode current collector terminal 23 as a current collector terminal, a negative electrode external terminal 24 as an external terminal, and a positive electrode external terminal 25 as an external terminal.

[0017] <Cover member 21> The lid member 21 is made of, for example, aluminum, and is a plate-like member extending in the longitudinal direction D. The lid member 21 is provided with a safety valve 21A and a cap 26 that closes the injection port 21B.

[0018] The safety valve 21A opens when the internal pressure of the battery case 70 reaches a predetermined pressure, and discharges gas generated inside the battery case 70.

[0019] The injection port 21B is a through-hole that passes through the lid member 21 in the vertical direction. The injection port 21B is used when injecting a nonaqueous electrolyte (not shown) into the battery case 70. A cap 26 is attached to the injection port 21B in an airtight and liquid-tight manner, for example, by laser welding.

[0020] <Negative electrode current collector terminal 22 and negative electrode external terminal 24> The negative electrode current collector terminal 22 and the negative electrode 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 electrode current collector terminal 22 is a rectangular plate-like member whose plate thickness direction is the depth direction E. The negative electrode external terminal 24 is electrically connected to the negative electrode current collector terminal 22 and exposed to the outside of the cover member 21.

[0021] <Positive electrode current collector terminal 23 and positive electrode external terminal 25> The positive electrode current collector terminal 23 and the positive electrode external terminal 25 are made of, for example, aluminum, and are provided at one end of the cover member 21 in the longitudinal direction D. The positive electrode current collector terminal 23 is a rectangular plate-like member whose plate thickness direction is the depth direction E. The positive electrode external terminal 25 is electrically connected to the positive electrode current collector terminal 23, and is exposed to the outside of the cover member 21.

[0022] (Wound body 30) As shown in FIGS. 2 and 5, the wound body 30 has a power generating body 31, a negative electrode current collecting portion 46, and a positive electrode current collecting portion .

[0023] As shown in Figs. 3, 5 and 6, the wound body 30 is composed of a laminate 68 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, and two long strip-shaped separators 60A and 60B. The negative electrode sheet 40, the positive electrode sheet 50, and the separators 60A and 60B are flexible. As shown in Figs. 5 and 6, the wound body 30 is composed by winding the laminate 68 around an imaginary axis IAX extending in the width direction G of the negative electrode sheet 40, the positive electrode sheet 50, and the separators 60A and 60B. As shown in Figs. 2 and 5, the wound body 30 has a flat shape.

[0024] <Negative electrode sheet 40> As shown in FIG. 3, the negative electrode sheet 40 includes 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 side negative electrode active material which is a portion on the negative electrode body 41 side, and an outer circumferential side negative electrode active material which is a portion on the opposite side of the negative electrode body 41. As shown in FIG. 3, the first negative electrode active material 42 and the second negative electrode active material 43 are coated only on the regions of both sides of the negative electrode body 41 except for the other side portions in the width direction G. Therefore, a negative electrode current collecting portion 46 on the other side in the width direction G of the negative electrode body 41 is formed, on which the first negative electrode active material 42 and the second negative electrode active material 43 are not applied.

[0025] <Positive electrode sheet 50> As shown in FIG. 3, the positive electrode sheet 50 includes 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 a large number of pores, and have an inner circumferential side positive electrode active material which is a portion on the positive electrode body 51 side, and an outer circumferential side positive electrode active material which is a portion on the opposite side of the positive electrode body 51. The positive electrode body 51 is made of, for example, aluminum foil. As shown in FIG. 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 except for one side portion in the width direction G. Therefore, a positive electrode current collecting portion 54 to which the first positive electrode active material 52 and the second positive electrode active material 53 are not coated is formed on one side portion in the width direction G of the positive electrode body 51.

[0026] <Separator 60A, 60B> The separators 60A and 60B are long strip-shaped members that electrically insulate the negative electrode sheet 40 and the positive electrode sheet 50 and have a large number of pores that allow the movement of charge carriers between the negative electrode sheet 40 and the positive electrode sheet 50. The separators 60A and 60B include a substrate layer 61 with a porous structure, a negative electrode side coating layer 62 provided on one surface of the substrate layer 61, and a positive electrode side coating layer 65 provided on the other surface of the substrate layer 61.

[0027] The base layer 61 is composed of a microporous sheet having many pores. The base layer 61 is produced by stretching a plasticizer-added film produced by a dry or wet process to form minute gaps (pores) through which the electrolyte can pass.

[0028] As shown in FIG. 3, the negative electrode side coat layer 62 includes a plurality of first coat layers 63 extending along the longitudinal direction LD of the separators 60A and 60B and spaced apart from each other in the width direction G (the first coat layer 63 of the separator 60B is not shown in FIG. 3). Each of the first coat layers 63 is provided over the entire longitudinal direction LD of the separators 60A and 60B. The number of the first coat layers 63 may be any number as long as there are more than one. On the other hand, the positive electrode side coat layer 65 includes a plurality of second coat layers 66 extending along the width direction G of the separators 60A and 60B and spaced apart from each other in the longitudinal direction LD (the second coat layer 66 of the separator 60A is not shown in FIG. 3). Each of the second coat layers 66 is provided over the entire width direction G of the separators 60A and 60B. The number of the second coat layers 66 may be any number as long as it is more than one, but it is preferable that two or more second coat layers 66 are provided on each half turn portion of the separators 60A and 60B when the wound body 30 described later is completed. Here, the half turn portion is half the size of the range of one turn of the separators 60A and 60B in the wound state. For example, when the separator 60A is wound only five times when the wound body 30 is completed, the separator 60A has ten half turn portions. When the separators 60A and 60B are viewed along the thickness direction of the separators 60A and 60B, the first coat layers 63 and the second coat layers 66 are perpendicular to each other.

[0029] The first coating layer 63 and the second coating layer 66 contain a filler. The first coating layer 63 and the second coating layer 66 are formed, for example, by binding the filler with a binder and bonding it in a layer on the base layer 61. There is no limit to the average particle size of the filler constituting the first coating layer 63 and the second coating layer 66. The average particle size of the filler constituting the first coating layer 63 and the second coating layer 66 is, for example, 50 nm to 300 nm. In this specification, the term "average particle size" refers to the cumulative 50% particle size (D50) in a volume-based particle size distribution obtained by a laser diffraction scattering method, unless otherwise specified.

[0030] The porosity of the first coating layer 63 and the second coating layer 66 is not strictly limited, but is larger than the porosity of the base material layer 61. For example, the porosity of the first coating layer 63 and the second coating layer 66 is 55 to 75%, and the porosity of the base material layer 61 is 40 to 50%. The porosity can be measured by, for example, the Archimedes method.

[0031] As shown in FIG. 3 and FIG. 4, the dimensions in the width direction G of the separators 60A and 60B are larger than those of the negative electrode sheet 40 and the positive electrode sheet 50. The negative electrode side coating layer 62 of the separator 60A faces the first negative electrode active material 42 of the negative electrode sheet 40, and the positive electrode side coating layer 65 of the separator 60A faces the first positive electrode active material 52 of the positive electrode sheet 50. Furthermore, the positive electrode side coating layer 65 of the separator 60B faces the second positive electrode active material 53 of the positive electrode sheet 50. That is, the negative electrode sheet 40, the separator 60A, the positive electrode sheet 50, and the separator 60B are laminated in this order, and the negative electrode sheet 40, the positive electrode sheet 50, and the separators 60A and 60B form a laminate 68. As shown in FIG. 4, one end of the positive electrode current collecting part 54 of the positive electrode body 51 in the width direction G is located on one side of the separators 60A and 60B. The other end of the negative electrode current collecting portion 46 of the negative electrode body 41 in the width direction G is located on the other side in the width direction G of the separators 60A, 60B.

[0032] The laminate 68 is wound around an imaginary axis IAX extending in the width direction G to form the wound body 30 shown in FIG. 2 and FIG. 5. In the wound body 30, the negative electrode side coating layer 62 of the separator 60B faces the second negative electrode active material 43 of the negative electrode sheet 40. 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 generating body 31. The power generating body 31 has a function of storing electric energy of the lithium ion secondary battery 10.

[0033] The lower end of the negative current collector terminal 22 is connected to the vertical center of the negative current collector 46 of the wound body 30 by ultrasonic welding, and the lower end of the positive current collector terminal 23 is connected to the vertical center of the positive current collector 54 by resistance welding. The negative current collector terminal 22, the positive current collector terminal 23, and the wound body 30 are housed together in the internal space of a battery case 70 filled with a nonaqueous electrolyte. The lid member 21 is then fixed to the upper end of the battery case 70 by laser welding, thereby completing the lithium-ion secondary battery 10 shown in FIG. 1. The upper opening of the battery case 70 is closed by the lid member 21 in an airtight and liquid-tight state.

[0034] When the lithium ion secondary battery 10 is completed in this manner, the nonaqueous electrolyte is impregnated into the numerous pores of the first negative electrode active material 42 and the second negative electrode active material 43 and the numerous pores of the first positive electrode active material 52 and the second positive electrode active material 53 in the battery case 70. Furthermore, the nonaqueous electrolyte is impregnated into the numerous pores of the base material layer 61, the numerous pores of the first coating layer 63, and the numerous pores of the second coating layer 66.

[0035] [Functions and Effects of Lithium-Ion Secondary Battery 10] When the lithium ion secondary battery 10 is charged and discharged, the negative electrode sheet 40 and the positive electrode sheet 50 repeatedly expand and contract. The negative electrode deformation amount, which is the amount of change between the shape of the negative electrode sheet 40 when expanded and the shape of the negative electrode sheet 40 when contracted, is greater than the positive electrode deformation amount, which is the amount of change between the shape of the positive electrode sheet 50 when expanded and the shape of the positive electrode sheet 50 when contracted. Furthermore, due to this expansion and contraction, the nonaqueous electrolyte (electrolyte) present in the voids (pores) of the negative electrode sheet 40 and the positive electrode sheet 50 during charging and discharging is discharged to the outside of the wound body 30 from both end faces in the width direction G of the negative electrode sheet 40 and the positive electrode sheet 50. Furthermore, due to the contraction of the negative electrode sheet 40 and the positive electrode sheet 50 during charging and discharging, the nonaqueous electrolyte (electrolyte) present on the outside of the wound 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, since the amount of deformation of the negative electrode is greater than the amount of deformation of the positive electrode, the amount of nonaqueous electrolyte discharged per unit time from both end faces in the width direction G of the negative electrode sheet 40 during charging and discharging, not passing through the separators 60A, 60B, is greater than the amount of nonaqueous electrolyte discharged per unit time from both end faces in the width direction G of the positive electrode sheet 50, not passing through the separators 60A, 60B. Furthermore, the amount of nonaqueous electrolyte returning per unit time from the outside of the wound body 30, not passing through the separators 60A, 60B, to the negative electrode sheet 40 during charging and discharging is greater than the amount of nonaqueous electrolyte returning per unit time from the outside of the wound body 30, not passing through the separators 60A, 60B, to the positive electrode sheet 50.

[0036] However, the separators 60A and 60B of this embodiment are provided with a negative electrode side coating layer 62 (multiple first coating layers 63) facing the negative electrode sheet 40 and a positive electrode side coating layer 65 (multiple second coating layers 66) facing the positive electrode sheet 50. As described above, the porosity of the first coating layer 63 and the second coating layer 66 is greater than the porosity of the substrate layer 61. Therefore, the nonaqueous electrolyte on the surface of the separators 60A and 60B facing the negative electrode sheet 40 tends to move in the longitudinal direction LD along the first coating layers 63, but does not move in the width direction G. Furthermore, the nonaqueous electrolyte on the surface of the separators 60A and 60B facing the positive electrode sheet 50 tends to move in the width direction G along the second coating layers 66, but does not move in the longitudinal direction LD. Therefore, the amount of nonaqueous electrolyte per unit time discharged from the negative electrode sheet 40 through the separators 60A, 60B to the outside of the wound body 30 from both end faces in the width direction G of the separators 60A, 60B during charging and discharging tends to be smaller than the amount of nonaqueous electrolyte per unit time discharged from the positive electrode sheet 50 through the separators 60A, 60B to the outside of the wound body 30 from both end faces in the width direction G of the separators 60A, 60B. Also, the amount of nonaqueous electrolyte per unit time returning from the outside of the wound body 30 through the separators 60A, 60B to the negative electrode sheet 40 during charging and discharging tends to be smaller than the amount of nonaqueous electrolyte per unit time returning from the outside of the wound body 30 to the positive electrode sheet 50 through the separators 60A, 60B.

[0037] In this way, when the wound body 30 is viewed as a whole, the difference between the amount of electrolyte movement between the outside of the wound body 30 and the negative electrode sheet 40 and the amount of electrolyte movement between the outside of the wound body 30 and the positive electrode sheet 50 when the lithium ion secondary battery 10 is charged and discharged is small. In other words, the difference between the amount of electrolyte movement between the outside of the wound body 30 and the negative electrode sheet 40 and the amount of electrolyte movement between the outside of the wound body 30 and the positive electrode sheet 50 is smaller than when the separators 60A and 60B do not include the negative electrode side coat layer 62 and the positive electrode side coat layer 65. Therefore, when the lithium ion secondary battery 10 is charged and discharged at a high rate, the lithium salt concentration of the nonaqueous electrolyte in the wound body 30 is less likely to become uneven, and therefore the high rate resistance is less likely to increase. Therefore, it is possible to suppress high rate deterioration of the lithium ion secondary battery 10.

[0038] Furthermore, the second coating layers 66 of the separators 60A, 60B are provided over the entire area of ​​the separators 60A, 60B in the width direction G. Therefore, the nonaqueous electrolyte is more likely to move between the separators 60A, 60B and the outside of the wound body 30 via the second coating layers 66 than when one end of each second coating layer 66 in the width direction G is located on the other side of one side edge of the separators 60A, 60B in the width direction G and the other end of each second coating layer 66 in the width direction G is located on one side of the other side edge of the separators 60A, 60B in the width direction G.

[0039] Furthermore, when the separators 60A, 60B are viewed along the thickness direction of the separators 60A, 60B, the first coat layers 63 and the second coat layers 66 of the separators 60A, 60B are perpendicular to each other. Therefore, compared to a case where the separators 60A, 60B are provided with only one of the first coat layer 63 and the second coat layer 66, for example, the thermal shrinkage of the separators 60A, 60B is more easily suppressed.

[0040] Although the battery according to the embodiment has been described above, the design of the battery can be appropriately modified without departing from the gist of the present invention.

[0041] For example, one end of each first coating layer 63 in the longitudinal direction LD may be located on the other side of one end of the separators 60A, 60B in the longitudinal direction LD, and the other end of each first coating layer 63 in the longitudinal direction LD may be located on one side of the other side edge of the separators 60A, 60B in the longitudinal direction LD.

[0042] In addition, the end portion on one side of the width direction G of each second coating layer 66 may be located on the other side of the end portion on one side of the width direction G of the separators 60A, 60B, and the end portion on the other side of the width direction G of each second coating layer 66 may be located on one side of the side edge portion on the other side of the width direction G of the separators 60A, 60B.

[0043] The porosity of the first coating layer 63 and the second coating layer 66 may be smaller than the porosity of the base layer 61. In this case, the nonaqueous electrolyte solution is more likely to move along a plurality of portions of the surface of the base layer 61 on the first coating layer 63 side that extend in the longitudinal direction LD where the first coating layer 63 is not formed. Furthermore, the nonaqueous electrolyte solution is more likely to move along a plurality of portions of the surface of the base layer 61 on the second coating layer 66 side that extend in the width direction G where the second coating layers 66 are not formed. [Explanation of symbols]

[0044] 10 Lithium-ion secondary battery (battery) 30 Wound body (electrode body) 40 Negative electrode sheet 50 Positive electrode sheet 60A Separator 60B Separator 61 Base material layer 63 First Coat Layer 66 Second Coat Layer

Claims

1. A battery comprising a wound body obtained by winding a laminate having a long strip-shaped negative electrode sheet, a long strip-shaped positive electrode sheet, and a long strip-shaped separator located between the negative electrode sheet and the positive electrode sheet, around a virtual axis extending in a width direction of the laminate, wherein the positive electrode sheet and the negative electrode sheet expand and contract due to charging and discharging, a change in shape between the expanded and contracted shapes of the negative electrode sheet is greater than a change in shape between the expanded and contracted shapes of the positive electrode sheet, The separator is A long strip-shaped base layer; a plurality of first coating layers provided on a surface of the base layer facing the negative electrode sheet, extending along the longitudinal direction of the separator and spaced apart from each other in the width direction, the first coating layers having a porosity different from that of the base layer; a plurality of second coating layers provided on a surface of the base layer facing the positive electrode sheet, extending along the width direction and spaced apart from each other in the longitudinal direction, the second coating layers having a porosity different from that of the base layer; A battery comprising:

2. The battery according to claim 1 , wherein the second coating layer has a larger porosity than the base material layer, and the second coating layer is provided over the entire base material layer in the width direction.

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