Secondary battery and separator for secondary battery

Abstract

This secondary battery comprises a separator. The separator comprises a sheet-form base material and a spacer that is disposed on the main surface of the base material. The base material is of elongate shape having a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction. The base material has a first region, a 2A-th region, and a 2B-th region that extend in the second direction. The 2A-th region and the 2B-th region are disposed on both sides in the first direction and overlap with both first-direction ends of a positive electrode mixture layer. The first region is disposed between the 2A-th region and the 2B-th region. The spacer has a plurality of linear parts, and the plurality of linear parts are arranged in a striped manner inclined with respect to the second direction. The spacer is disposed in the first region, whereas no spacer is disposed in the 2A-th region or the 2B-th region.

Description

Secondary batteries and separators for secondary batteries Cross-reference of related applications

[0001] This disclosure claims priority with respect to Japanese Patent Application No. 2024-170816, filed with the Japan Patent Office on 30 September 2024, and the entirety of the said patent application is incorporated herein by reference.

[0002] This disclosure relates to secondary batteries and separators for secondary batteries.

[0003] A secondary battery comprises an electrode group and a non-aqueous electrolyte. The electrode group includes a positive electrode, a negative electrode, and a separator placed between the positive and negative electrodes. Examples of secondary batteries include lithium-ion batteries and lithium secondary batteries (lithium metal secondary batteries). In the negative electrode of a lithium secondary battery, lithium metal is deposited during charging, and the lithium metal dissolves into the non-aqueous electrolyte during discharge.

[0004] To suppress volume changes in the electrode group during charging and discharging, it is conceivable to place a spacer between the separator substrate and the positive or negative electrode. In lithium secondary batteries, the spacer creates a space for accommodating the lithium metal deposited on the negative electrode during charging.

[0005] Patent Document 1 proposes a lithium secondary battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte having lithium ion conductivity, wherein lithium metal is deposited on the negative electrode during charging, and the lithium metal dissolves from the negative electrode during discharge, and a spacer is provided between at least one of the positive electrode and the negative electrode and the separator, the first length of the separator in a first direction D1 is smaller than the second length in a second direction D2 intersecting the first direction D1, and at least one of the angle on the spacer side formed by the separator and the spacer, and the angle on the spacer side formed by the electrode in contact with the spacer and the spacer, is greater than 90° in the cross section of the spacer cut along the thickness direction of the separator and the first direction D1.

[0006] International Publication No. 2021 / 192645

[0007] In recent years, there has been a growing demand for improved reliability in rechargeable batteries equipped with spacers.

[0008] One aspect of the present disclosure comprises a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode current collector and a positive electrode composite layer supported on the positive electrode current collector, the separator includes a sheet-like substrate and a spacer disposed on the main surface of the substrate, the substrate has an elongated shape having a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction, and the substrate has a first region, a second A region and a second A region extending in the second direction The present invention relates to a secondary battery having a second A region and a second B region, wherein the second A region and the second B region are arranged on both sides in the first direction and overlap with both ends of the positive electrode composite layer in the first direction, the first region is arranged between the second A region and the second B region, the spacer has a plurality of linear portions, the plurality of linear portions are arranged in a stripe shape inclined with respect to the second direction, the spacer is arranged in the first region, and the spacer is not arranged in the second A region and the second B region.

[0009] Another aspect of the present disclosure relates to a separator for a secondary battery, comprising a sheet-like substrate and a spacer disposed on the main surface of the substrate, wherein the substrate has an elongated shape having a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction, the substrate has a first region, a second A region and a second B region extending in the second direction, the second A region and the second B region being located on both sides of the first direction, the first region being located between the second A region and the second B region, the spacer having a plurality of linear portions, the plurality of linear portions being arranged in a stripe pattern inclined with respect to the second direction, the spacer being located in the first region, and the spacer not being located in the second A region and the second B region.

[0010] According to this disclosure, the reliability of secondary batteries can be improved.

[0011] Novel features of the present invention are described in the appended claims, but the present invention, both in terms of structure and content, and in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in conjunction with the drawings.

[0012] This is a schematic top view showing an example of a separator according to the embodiment of this disclosure. This is a schematic top view showing another example of a separator according to the embodiment of this disclosure. This is a schematic top view showing yet another example of a separator according to the embodiment of this disclosure. This is a schematic top view showing yet another example of a separator according to the embodiment of this disclosure. This is a schematic top view showing yet another example of a separator according to the embodiment of this disclosure. This is a schematic longitudinal cross-sectional view showing an example of a secondary battery according to the embodiment of this disclosure. This is a schematic cross-sectional view showing the main part of the electrode group. This is a schematic top view showing a separator provided in comparative example battery B1.

[0013] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits are given as examples for numerical values ​​of specific physical properties or conditions, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit does not exceed the upper limit.

[0014] A separator for a secondary battery according to the embodiment of this disclosure includes a sheet-like substrate and a spacer disposed on the main surface of the substrate. The substrate has an elongated shape with a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction. The first direction is also referred to as the width direction. The second direction is also referred to as the length direction. The substrate has a first region, a second A region, and a second B region extending in the second direction. The second A region and the second B region are located on both sides of the first direction and overlap with both ends of the positive electrode composite layer in the first direction. The first region is located between the second A region and the second B region, and the spacer has a plurality of linear portions, which are arranged in a stripe pattern inclined with respect to the second direction. The spacer is located in the first region, but not in the second A region and the second B region.

[0015] Furthermore, the secondary battery according to the embodiment of this disclosure comprises a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. The separator is the above-described separator for secondary batteries. The positive electrode includes a positive electrode current collector and a positive electrode composite material layer supported on the positive electrode current collector. The second A region and the second B region, located on both sides in the first direction, overlap with both ends of the positive electrode composite material layer in the first direction. As a result, the spacer is positioned so as not to overlap with both ends of the positive electrode composite material layer in the first direction.

[0016] The arrangement pattern in which multiple linear sections are inclined with respect to a second direction and arranged in a stripe-like pattern improves the reliability of the electrode group and thus the reliability of the battery. Specifically, a separator can be stably placed between the positive and negative electrodes, and the distance between the positive and negative electrodes can be stably maintained. The electrode group can be stably constructed. For example, a columnar wound electrode group with a predetermined diameter can be stably obtained. The space formed between the positive and negative electrodes can be stably maintained by the spacer.

[0017] On the other hand, in the case of the above-described arrangement pattern, many portions where a plurality of linear portions and both end portions of the positive electrode composite material layer in the first direction intersect and overlap are formed. In the vicinity of the above overlapping portions, the stress applied to the base material is locally concentrated, whereby the base material may be damaged and an internal short circuit may occur. In particular, in the vicinity of the side of the above overlapping portion that forms an acute angle with respect to the second direction of the linear portion (for example, the portion P of the base material 50 in FIG. 8), the stress is likely to concentrate.

[0018] The end portion of the positive electrode in the first direction faces the end portion of the Li deposition region (Li ion occlusion region) of the negative electrode. For example, during charging, Li ions released from the positive electrode move to the negative electrode so as to go around the spacer (protrusion), and the negative electrode expands due to the deposition of Li (occlusion of Li ions). As a result, in the vicinity of the overlapping portion between the end portion of the positive electrode in the first direction and the spacer, the stress applied to the base material may locally increase due to the expansion of the negative electrode. In particular, in a lithium secondary battery, an edge portion of the deposited Li is likely to be thickly formed in the vicinity of the overlapping portion between the end portion of the positive electrode in the first direction and the spacer, and the stress applied to the base material is likely to locally increase as Li is deposited. Further, the positive electrode composite material layer is slightly smaller in length in the width direction than the negative electrode composite material layer, and the positive electrode is thicker than the negative electrode. In the vicinity of the above overlapping portion, since the influence of the thickness change (step) generated at the boundary between the portion of the base material facing the positive electrode and the portion not facing the positive electrode is large, the stress applied to the base material may locally increase.

[0019] On the other hand, in the present disclosure, by forming the above-described second A region and second B region, the spacer can be arranged so that the spacer and both end portions of the positive electrode composite material layer in the first direction do not overlap, thereby suppressing the above stress concentration. As a result, damage to the base material and the accompanying internal short circuit can be suppressed.

[0020] When a plurality of linear portions are arranged in a stripe shape inclined with respect to the second direction, in the vicinity of the side of the above overlapping portion that forms an acute angle with respect to the second direction of the linear portion (for example, the portion P of the base material 50 in FIG. 8), the stress applied to the base material is likely to locally increase. Therefore, the effect of suppressing the above stress concentration by the separator of the present disclosure can be remarkably obtained.

[0021] In this disclosure, a plurality of linear portions constituting the spacer are arranged in a stripe pattern, inclined with respect to a second direction. That is, each of the plurality of linear portions is straight, spaced apart from each other and arranged parallel to each other. The angle θ (acute angle) of each of the plurality of linear portions with respect to the second direction may be 5° or more, 10° or more, 30° or more, 45° or more, or 60° or more. Furthermore, the above angle θ may be 85° or less, 80° or less, or 75° or less.

[0022] The ratio of the length L2 of the substrate in the second direction to the length L1 of the substrate in the first direction, L2 / L1, is greater than 1, for example, it may be 1.4 or greater, or 5.0 or greater. Also, L2 / L1 may be 100.0 or less, or 50.0 or less.

[0023] Region 2A is formed on one end side of the substrate in the first direction, and the length W2A of region 2A in the first direction can also be said to be the distance from one of the two sides of the rectangular substrate in a plan view that extend in the second direction. Region 2B is formed on the other end side of the substrate in the first direction, and the length W2B of region 2B in the first direction can also be said to be the distance from the other side of the two sides of the rectangular substrate in a plan view that extend in the second direction.

[0024] The lengths of the second A region and the second B region in the first direction (widths of the second A region and the second B region) W2A and W2B are not particularly limited and can be appropriately determined within a range where the second A region, the second B region and both ends of the positive electrode composite layer in the first direction overlap appropriately. W2A and W2B can be appropriately determined within a range where the stability of space formation by the spacer is ensured and the concentration of the above-mentioned stress is suppressed. W2A and W2B may be 1.5 mm or more, 2.0 mm or more, or 2.5 mm or more, respectively. Also, W2A and W2B may be 20 mm or less, or 15 mm or less, respectively. If the length L1 of the base material in the first direction is 60 mm or less, W2A and W2B may be 2.5 mm or more and L1 × 0.25 mm or less, respectively. If the length L1 of the base material in the first direction is greater than 60 mm, W2A and W2B may be 2.5 mm or more and 15 mm or less, respectively.

[0025] Areas where the second A region and the second B region face both ends of the positive electrode composite layer in the first direction are regions each having a certain width extending in the second direction. For example, in the case of FIG. 1, the region where the second A region P2A faces the end E1 of the positive electrode composite layer 11b in the first direction (D1 direction) is a region having a width WE1 extending in the second direction (D2 direction). The region where the second B region P2B faces the end E2 of the positive electrode composite layer 11b in the first direction (D1 direction) is a region having a width WE2 extending in the second direction (D2 direction). WE1 and WE2 may each be 1.5 mm or more, or may each be 2.0 mm or more. Also, WE1 and WE2 may each be 15 mm or more, or may each be 10 mm or less. WE1 and WE2 may, for example, each be 2.0 mm or more and 15.0 mm or less (or 12.0 mm or less). The second A region P2A and the second B region P2B in FIGS. 2 to 5 may also have the same width as described above.

[0026] The length of the first region in the first direction (width of the first region) W1 may, for example, be 10.0 mm or more, or may be 20.0 mm or more. Also, W1 may, for example, be 100.0 mm or less, or may be 60.0 mm or less. W2A / W1 may be 0.01 or more and 0.5 or less, or may be 0.05 or more and 0.3 or less. W2B / W1 may also be within the range exemplified by the above W2A / W1.

[0027] W2A / W2B may be 0.5 or more and 2.0 or less, or may be 0.8 or more and 1.25 or less. It is preferable that W2A and W2B are substantially equal to each other.

[0028] The base material further has a fourth A region and a fourth B region that are disposed on both sides of the first region in the second direction and overlap both ends of the positive electrode composite layer in the second direction, and spacers may not be disposed in the fourth A region and the fourth B region. In this case, the first region is disposed between the fourth A region and the fourth B region in the second direction. Local concentration of stress applied to the base material in the vicinity of the overlapping portions of both ends of the positive electrode composite layer in the second direction and the spacers is suppressed, and damage to the base material is suppressed. The base material may have either one of the above fourth A region and fourth B region.

[0029] Region 4A is formed on one end side of the substrate in the second direction, and the length W4A of region 4A in the second direction can also be said to be the distance from one of the two sides of the rectangular substrate in a plan view that extend in the first direction. Region 4B is formed on one end side of the substrate in the second direction, and the length W4B of region 4B in the second direction can also be said to be the distance from one of the two sides of the rectangular substrate in a plan view that extend in the first direction.

[0030] The lengths in the second direction of the 4A and 4B regions (widths of the 4A and 4B regions) W4A and W4B are not particularly limited. If the length L1 of the substrate in the second direction is 1500 mm or less, W4A and W4B may be 2.0 mm or more (or 2.5 mm or more) and L2 × 0.01 mm or less, respectively. If the length L2 of the substrate in the second direction is greater than 1500 mm, W4A and W4B may be 2.0 mm or more (or 2.5 mm or more) and 15 mm or less, respectively.

[0031] The regions of the 4A region and the 4B region facing both ends of the positive electrode composite layer in the second direction are regions having a certain width extending in the first direction. For example, in Figure 5, the region of the 4A region P4A facing the end E3 of the positive electrode composite layer 11b in the second direction (D2 direction) is a region having a width WE3 extending in the first direction (D1 direction). The region of the 4B region P4B facing the end E4 of the positive electrode composite layer 11b in the second direction (D2 direction) is a region having a width WE4 extending in the first direction (D1 direction). WE3 and WE4 may be, for example, 2.0 mm or more and 15.0 mm or less (or 12.0 mm or less).

[0032] Any of the multiple linear sections may be arranged continuously. At least some of the multiple linear sections may be arranged intermittently and may have one or more defects. In this case, the ratio of the total length of the defects contained in one linear section to the length of one linear section may be 5% or more and 30% or less, or 10% or more and 25% or less.

[0033] The ratio of the length of one defect contained in one linear portion to the length of one linear portion may be 5% or more and 30% or less, or 10% or more and 25% or less. The length of one defect may be, for example, 0.1 mm or more and 1.0 mm or less, or 0.2 mm or more and 0.8 mm or less.

[0034] From the viewpoint of ensuring the stability of space formation by the spacer, in a plan view of the positive electrode, the ratio of the area of ​​the region where the positive electrode composite material layer faces the first region to the area of ​​the positive electrode composite material layer may be 50% or more, or 60% or more. Also, from the viewpoint of improving liquid flowability, in a plan view of the positive electrode, the ratio of the area of ​​the region where the positive electrode composite material layer faces the first region to the area of ​​the positive electrode composite material layer may be 80% or less, or 70% or less. In a plan view of the positive electrode, the ratio of the area of ​​the region where the positive electrode composite material layer faces the first region to the area of ​​the positive electrode composite material layer may be, for example, 50% or more, or 80% or less.

[0035] Preferably, the first region includes a first A region and a first B region extending in a second direction, the spacer includes a first spacer and a second spacer, the plurality of linear portions include a plurality of first linear portions and a plurality of second linear portions, the first spacer has a plurality of first linear portions, the second spacer has a plurality of second linear portions, the first spacer is disposed in the first A region, the second spacer is disposed in the first B region, a third region extending in a second direction is formed between the first A region and the first B region, and neither the first spacer nor the second spacer is disposed in the second A region, the second B region, and the third region.

[0036] By providing a third region, the reduction in fluid flowability of the electrode group due to spacers is suppressed, and the reduction in cycle characteristics (capacity retention rate) due to the reduction in fluid flowability is suppressed. By arranging the first spacer and the second spacer in the first A region and the first B region on both sides of the third region, the stability of space formation by the spacers is sufficiently ensured.

[0037] The first A region, the first B region, and the third region each extend in the second direction, and the third region is formed between the first A region and the first B region in the first direction. As a result, the fluid flow is easily improved uniformly throughout the entire opposing region between the positive and negative electrodes (in the winding direction in the case of a wound electrode group), and a significant improvement in fluid flow is obtained. Multiple spaces formed between adjacent first linear portions (second linear portions) each connect to the spaces formed in the third region, which makes it easy to significantly improve fluid flow.

[0038] It is preferable that the multiple first linear portions and the multiple second linear portions are inclined in opposite angular directions with respect to the second direction, and more preferably arranged mirror-symmetrically with respect to the third region. In this case, meandering of the separator is suppressed when the separator is transported by a roll-to-roll method, the electrode group can be stably configured, and the reliability of the battery is improved. Alternatively, the multiple first linear portions and the multiple second linear portions may be inclined in the same angular direction with respect to the second direction.

[0039] From the viewpoint of uniformity of surface pressure of the electrode group, it is preferable that the first linear portion has approximately the same height as the second linear portion. The first linear portion may have a different width dimension from the second linear portion, but from the same viewpoint, it is preferable that it has approximately the same width.

[0040] Although no linear portion is placed in the third region, several small, dot-shaped spacers (protrusions) may be dispersed in the third region, provided that the fluid flow is not impaired. The ratio of the area of ​​the dot-shaped spacers placed in the third region to the total area of ​​the third region is, for example, 3% or less or 2% or less.

[0041] Secondary batteries include lithium secondary batteries (lithium metal secondary batteries) and lithium-ion batteries. For example, the negative electrode of a lithium secondary battery is an electrode in which lithium metal is deposited during charging and dissolves in a non-aqueous electrolyte during discharge. The negative electrode of a lithium-ion battery is an electrode in which lithium ions are absorbed into the negative electrode active material during charging and released from the negative electrode active material during discharge.

[0042] An electrode group is composed of a positive electrode, a negative electrode, and a separator. For example, an electrode group may be formed by laminating or winding a positive electrode, a negative electrode, and a separator (a base material on which a spacer is placed). An electrode group may also be formed by laminating a positive electrode, a negative electrode, and a separator in a zigzag pattern. The outer shape of a wound electrode group may be cylindrical or elliptical. Typically, a wound electrode group uses a long positive electrode, a negative electrode, and a separator, and the length direction of the positive electrode, negative electrode, and separator is the winding direction.

[0043] Here, Figures 1 to 5 are schematic top views showing examples of separators according to the embodiments of this disclosure. Each figure is a top view of the separator in plan view. Each figure is a schematic diagram, and the aspect ratios of the length and width of each component do not necessarily reflect the actual dimensions. The elongated positive electrode 11 (positive electrode composite layer 11b) facing the elongated base material 50 is represented by a dashed line. Note that the separators of this disclosure are not limited to this. In Figures 1 to 5, D1 is the width direction of the base material 50 and the positive electrode 11 (positive electrode composite layer 11b), and D2 is the length direction of the base material 50 and the positive electrode 11 (positive electrode composite layer 11b). A space 14s is formed between the positive and negative electrodes by the spacer 53.

[0044] In a plan view, the elongated positive electrode 11 (positive electrode composite layer 11b) has a rectangular shape. The ends E1 to E4 of the positive electrode composite layer are ends that extend along the four sides of the rectangle. The ends E1 and E2 of the positive electrode composite layer in the width direction (first direction) are ends that extend along two of the four sides of the rectangle in the length direction. The ends E1 and E2 of the positive electrode composite layer in the length direction (second direction) are ends that extend along two of the four sides of the rectangle in the width direction.

[0045] The separators in Figures 1-5 comprise a sheet-like base material 50 and a spacer 53 arranged on one main surface of the base material 50. The base material 50 has a long shape with a length L1 in a first direction (D1 direction) and a length L2 (L1 < L2) in a second direction (D2 direction) perpendicular to the first direction. The base material 50 has a first region P1, a second A region P2A, and a second B region P2A extending in the second direction. The second A region P2A and the second B region P2B are arranged on both sides in the first direction and overlap with the ends E1 and E2 of the positive electrode composite layer 11b in the first direction. The first region P1 is located between the second A region and the second B region. The spacer 53 has a plurality of linear portions 63. The plurality of linear portions 63 are arranged in a stripe pattern inclined with respect to the second direction. The spacer 53 is located in the first region P1. Spacers 53 are not placed in the second A region P2A and the second B region P2A. In other words, the spacers 53 are positioned so as not to overlap with the ends E1 and E2 of the positive electrode composite layer 11b in the second direction.

[0046] Near the overlapping points between the positive electrode composite layer and the spacer (linear portion) in the first direction (particularly at point P in Figure 8), stress on the substrate can be locally concentrated, potentially damaging the substrate and causing an internal short circuit. By using the separators shown in Figures 1-5, the above-mentioned stress concentration can be suppressed, thereby preventing damage to the substrate.

[0047] In Figure 1, the multiple linear portions 63 are arranged in a stripe pattern, inclined with respect to the second direction. The multiple linear portions 63 are arranged parallel to each other at a predetermined interval N, where N is the shortest distance between adjacent linear portions 63.

[0048] The inclination angle θ (acute angle) of the linear portion 63 with respect to the second direction may be 5° or more and 75° or less, or 10° or more and 60° or less. The width LW of the linear portion 63 may be 0.1 mm or more, 0.2 mm or more, 0.3 mm or more, or 0.5 mm or more. Also, the width LW of the linear portion 63 may be 2 mm or less, or 1.5 mm or less. The spacing N of the linear portions 63 may be 1.0 mm or more and 5.0 mm or less, or 2.0 mm or more and 4.0 mm or less.

[0049] The width W1 of the first region in Figure 1 may be, for example, 10 mm or more and 100 mm or less, or 20 mm or more and 60 mm or less. The widths W2A of the second region P2A and W2B of the second region P2B are approximately equal to each other and may be 1.5 mm or more and 20 mm or less, or 2.0 mm or more and 15 mm or less, respectively. W2A / W1 and W2B / W1 may be 0.01 or more and 0.5 or less, or 0.05 or more and 0.3 or less, respectively.

[0050] In Figures 2-5, the first region P1 includes a first A region P1A and a first B region P1B, which extend in a second direction. The spacer 53 includes a first spacer 53a and a second spacer 53b. The plurality of linear portions 63 include a plurality of first linear portions 63a and a plurality of second linear portions 63b. The first spacer 53a has a plurality of first linear portions 63a, and the second spacer 53b has a plurality of second linear portions 63b. The first spacer 53a is located in the first A region P1A, and the second spacer 53b is located in the first B region P1B. A third region P3 extending in a second direction is formed between the first A region P1A and the first B region P1B.

[0051] In Figures 2-5, neither the first spacer 53a nor the second spacer 53b is placed in the second A region P2A, the second B region P2B, and the third region P3. In Figure 4, neither the first spacer 53a nor the second spacer 53b is placed in the fourth A region P4A. In Figure 5, neither the first spacer 53a nor the second spacer 53b is placed in the fourth A region P4A and the fourth B region P4B.

[0052] Multiple first linear portions 63a are arranged in a stripe pattern, inclined with respect to the second direction. Multiple first linear portions 63a are arranged parallel to each other at a predetermined interval N1. N1 is the shortest distance between adjacent first linear portions. Multiple second linear portions 63b are arranged in a stripe pattern, inclined with respect to the second direction. Multiple second linear portions 63b are arranged parallel to each other at a predetermined interval N2. N2 is the shortest distance between adjacent second linear portions.

[0053] In Figure 2, the multiple first linear portions 63a and the multiple second linear portions 63b are inclined toward each other in the same angular direction.

[0054] In Figures 3 to 5, the multiple first linear portions 63a and the multiple second linear portions 63b are inclined in opposite angular directions with respect to the second direction. In Figures 3 to 5, they are arranged mirror-symmetrically with respect to the third region P3. In Figures 3 to 5, the end of the first linear portion 63a on the third region P3 side and the end of the second linear portion 63b on the third region P3 side are positioned at approximately the same location in the first direction (direction D1), but they may be positioned at different locations in the first direction (direction D1).

[0055] Multiple first linear portions 63a are arranged at approximately constant intervals N1. Multiple second linear portions 63b are arranged at approximately constant intervals N2. Each of the multiple first linear portions 63a has approximately the same width LW1. Each of the multiple second linear portions 63b has approximately the same width LW2.

[0056] The inclination angle θ1 (acute angle) of the first linear portion 63a with respect to the second direction may be 5° or more and 75° or less, or 10° or more and 60° or less. The width LW1 of the first linear portion 63a may be 0.1 mm or more, 0.2 mm or more, 0.3 mm or more, or 0.5 mm or more. Also, the width LW1 of the first linear portion 63a may be 2 mm or less, or 1 mm or less. The spacing N1 of the first linear portions 63a may be 1.0 mm or more and 5.0 mm or less, or 2.0 mm or more and 4.0 mm or less. The inclination angle θ2, spacing N2, and width LW2 of the second linear portion 63b may be within the ranges exemplified above for the inclination angle θ1, spacing N1, and width LW1 of the first linear portion 63a, respectively.

[0057] In Figures 2-5, the inclination angle θ1 (acute angle) of the first linear portion 63a with respect to the second direction is approximately the same as the inclination angle θ2 (acute angle) of the second linear portion 63b with respect to the second direction. The spacing N1 (shortest distance between the first linear portions) of the first linear portions is approximately the same as the spacing N2 (shortest distance between the first linear portions) of the second linear portions. The width LW1 of the first linear portion is approximately the same as the width LW2 of the second linear portion.

[0058] In Figures 3 to 5, the inclination angle θ1, spacing N1, and width LW1 of the first linear portion 63a are approximately the same as the inclination angle θ2, spacing N2, and width LW2 of the second linear portion 63b, respectively. However, if the multiple first linear portions and the multiple second linear portions satisfy all of the following conditions (i) to (iii), they are considered to be mirror-symmetric.

[0059] (i) The difference between the inclination angle θ1 of the first linear section and the inclination angle θ2 of the second linear section is within the range of -15° or more and 15° or less. (ii) The spacing N1 of the first linear section and the spacing N2 of the second linear section satisfy the following relationship: (absolute value of N1 - N2) / (average value of N1 and N2) ≤ 0.3 (iii) The width LW1 of the first linear section and the width LW2 of the second linear section satisfy the following relationship: (absolute value of LW1 - LW2) / (average value of LW1 and LW2) ≤ 0.3

[0060] In the cases of Figures 2 to 5, for example, the width W1A of the first region A P1A and the width W1B of the first region B P1B may be approximately equal to each other, and may be 10 mm or more and 60 mm or less, respectively. W2A / W1A and W2B / W1B may be 0.01 or more and 0.7 or less, or 0.05 or more and 0.4 or less, respectively. In the cases of Figures 2 to 5, for example, the width W2A of the second region A P2A and the width W2B of the second region B P2B may be approximately equal to each other, and may be 1.5 mm or more and 20 mm or less, or 2.5 mm or more and 15 mm or less, respectively.

[0061] The width W3 of the third region P3 may be 1.0 mm or more, 2.0 mm or more, or 2.5 mm or more. The width W3 of the third region P3 may be, for example, 1.0 mm or more (or 2.0 mm or more) and 20.0 mm or less, or 1.0 mm or more (or 2.0 mm or more) and 10 mm or less. W3 / W1A and W3 / W1B may be 0.1 or more or 0.2 or more, or 0.7 or less or 0.5 or less, respectively. W3 / W1A and W3 / W1B may be 0.05 or more (or 0.1 or more) and 0.7 or less, or 0.1 or more and 0.5 or less, respectively. The width W3 of the third region P3 is sufficiently larger than the length N1 of the first defect 73a and the length N2 of the second defect 53b.

[0062] The ratio of the area of ​​the positive electrode composite layer 11b to the area of ​​the region facing the first region P1 (or the region formed by the first A region P1A and the first B region P1B) may be 50% or more, or 50% or more and 80% or less.

[0063] As shown in Figure 5, at least a portion of the plurality of first linear portions 63a may have one or more first defects 73a. The ratio of the total length of the first defects 73a included in one first linear portion 63a to the length of one first linear portion 63a may be 5% or more and 30% or less, or 10% or more and 25% or less.

[0064] The ratio of the length of one first defect portion 73a contained in one first linear portion 63a to the length of one first linear portion 63a may be 5% or more and 30% or less, or 10% or more and 25% or less. The length of one first defect portion may be, for example, 0.1 mm or more and 1.0 mm or less, or 0.2 mm or more and 0.8 mm or less.

[0065] As shown in Figure 5, each of the multiple second linear portions 63b may have one or more second defect portions 73b. The ratio of the total length of the second defect portions 73b included in one second linear portion 63b to the length of one second linear portion 63b may be 5% or more and 30% or less, or 10% or more and 25% or less.

[0066] The ratio of the length of one second defect portion 73b contained in one second linear portion 63b to the length of one second linear portion 63b may be 5% or more and 30% or less, or 10% or more and 25% or less. The length of one second defect portion 63b may be, for example, 0.1 mm or more and 1.0 mm or less, or 0.2 mm or more and 0.8 mm or less.

[0067] In Figure 4, the base material 50 is positioned on one side of the first region P1 in the second direction and has a fourth A region P4A that overlaps with the end E3 of the positive electrode composite layer 11b in the second direction (length direction). In the second direction (length direction) of the positive electrode composite layer 11b, the fourth A region P4A is positioned on one side of the first region P1 in the second direction. No spacer 53 is positioned in the fourth A region P4A. In Figure 4, the spacer 53 is positioned so as not to overlap with the end E3 of the positive electrode composite layer 11b in the second direction (length direction).

[0068] In Figure 5, the base material 50 is arranged on both sides of the first region P1 in the second direction and has a fourth A region P4A and a fourth B region P4B that overlap with both ends E3 and E4 in the second direction (length direction) of the positive electrode composite layer 11b. In the second direction (length direction) of the positive electrode composite layer 11b, the first region P1 is arranged between the fourth A region P4A and the fourth B region P4B. No spacers 53 are placed in the fourth A region P4A and the fourth B region P4B. In Figure 5, the spacers 53 are arranged so as not to overlap with both ends E3 and E4 in the second direction (length direction) of the positive electrode composite layer 11b.

[0069] In the case of a wound electrode group, one of the two ends E3 and E4 of the positive electrode 11 in the second direction is the winding start end, and the other of the two ends E3 and E4 of the positive electrode 11 in the second direction is the winding end.

[0070] Near the overlapping points between the positive electrode composite layer (both ends, or one end) and the spacer (linear portion) in the second direction, stress on the substrate can concentrate locally, potentially damaging the substrate and causing an internal short circuit. By using the separators shown in Figures 4-5, the damage to the substrate due to the above-mentioned stress concentration can be suppressed. Since stress is particularly likely to occur at the winding start end, it is preferable to position the spacer so that it does not overlap with the winding start end of the positive electrode.

[0071] The elongated positive electrode 11 may have a current collector exposed portion in a part near the center in the length direction where the positive electrode composite layer 11b is not supported along the width direction. A positive electrode lead, for example, is connected to the current collector exposed portion.

[0072] Secondary batteries include lithium secondary batteries (lithium metal secondary batteries) and lithium-ion batteries. For example, the negative electrode of a lithium secondary battery is an electrode in which lithium metal is deposited during charging and dissolves in a non-aqueous electrolyte during discharge. The negative electrode of a lithium-ion battery is an electrode in which lithium ions are absorbed into the negative electrode active material during charging and released from the negative electrode active material during discharge.

[0073] An electrode group is composed of a positive electrode, a negative electrode, and a separator. For example, an electrode group may be formed by laminating or winding a positive electrode, a negative electrode, and a separator (a base material on which a spacer is placed). An electrode group may also be formed by laminating a positive electrode, a negative electrode, and a separator in a zigzag pattern. The outer shape of a wound electrode group may be cylindrical or elliptical. Typically, a wound electrode group uses a long positive electrode, a negative electrode, and a separator, and the length direction of the positive electrode, negative electrode, and separator is the winding direction.

[0074] A positive electrode in which a positive electrode composite layer is supported on one main surface of the positive electrode current collector may be used, and the negative electrode and the separator according to the embodiment of this disclosure may be arranged on the side of the positive electrode where the positive electrode composite layer is supported. Alternatively, a positive electrode in which a positive electrode composite layer is supported on both main surfaces of the positive electrode current collector may be used, and the negative electrode and the separator according to the embodiment of this disclosure may be arranged on both sides of the positive electrode. For example, in a wound electrode group, the negative electrode and the separator according to the embodiment of this disclosure are arranged on both sides of the positive electrode (outer circumference side and inner circumference side).

[0075] (Separator) The separator comprises a sheet-like substrate and a spacer placed on the main surface of the substrate. In a plan view of the substrate, the ratio of the area of ​​the region where the substrate faces the spacer to the area of ​​the substrate may be 5% or more and 25% or less.

[0076] (Substrate) A porous sheet having ion permeability and insulating properties is used as the substrate. Examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the porous sheet is not particularly limited, but it may be a polymer material. Examples of polymer materials include olefin resins, polyamide resins, and cellulose. Examples of olefin resins include polyethylene, polypropylene, and copolymers of ethylene and propylene. The substrate may contain additives as needed. Examples of additives include inorganic fillers.

[0077] The thickness of the substrate is not particularly limited, but is, for example, 5 μm or more and 20 μm or less, and more preferably 10 μm or more and 20 μm or less.

[0078] The substrate may include a porous sheet and a composite material layer (heat-resistant layer). The composite material layer may be formed on one main surface of the porous sheet or on both main surfaces. The composite material layer is a layer that allows lithium ions to pass through. The composite material layer contains inorganic particles. The composite material layer may optionally contain a resin material. The thickness of the composite material layer may be 5% to 50% of the total thickness of the substrate.

[0079] The composite material layer may be positioned on the side of the porous sheet facing the positive electrode, or on the side of the porous sheet facing the negative electrode. When the composite material layer is positioned on the positive electrode side, degradation of the porous sheet due to oxidation can be suppressed. When the composite material layer is positioned on the negative electrode side, degradation of the porous sheet due to reduction can be suppressed. A spacer may be placed on the composite material layer. In this case, the effect of suppressing thermal shrinkage of the substrate is particularly enhanced.

[0080] The inorganic particles are preferably inorganic compound particles that have thermal stability and insulating properties, and are less likely to melt and decompose when abnormal heat is generated due to a short circuit in the battery, etc. Examples of inorganic particle materials include oxides, hydroxides, nitrides, carbides, and sulfides. Examples of oxides include aluminum oxide, boehmite, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide, yttrium oxide, and zinc oxide. Examples of nitrides include silicon nitride, aluminum nitride, boron nitride, and titanium nitride. Examples of carbides include silicon carbide and boron carbide. Examples of sulfides include barium sulfate. Examples of hydroxides include aluminum hydroxide. The median diameter in the volume-based particle size distribution of the inorganic particles may be 0.2 to 2.0 μm.

[0081] The median diameter in the volume-based particle size distribution of inorganic particles can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer (e.g., Microtrac manufactured by Nikkiso Co., Ltd.). Alternatively, the cross-section of the substrate can be observed with a transmission electron microscope (TEM), a TEM image can be taken, the area enclosed by the contours of 100 arbitrary inorganic particles can be calculated, the diameter of an equivalent circle (true circle) having the same area as the calculated area can be determined, and the median diameter can be calculated as the average of the diameters of the 100 equivalent circles.

[0082] Examples of resin materials included in the composite material layer include fluorine-containing resins such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene, fluorine-containing rubbers such as vinylidene fluoride-tetrafluoroethylene copolymer and ethylene-tetrafluoroethylene copolymer, styrene-butadiene copolymer or its hydride, acrylonitrile-butadiene copolymer or its hydride, methacrylic acid ester-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl alcohol, polyvinyl acetate, and other rubbers. Examples include cellulose derivatives such as ethylcellulose, methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose; acrylic resins such as acrylic acid-metharyl acid copolymers; polyamides such as polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyimide, and fully aromatic polyamides (aramids); polyamideimide; polyacrylonitrile; polyvinyl alcohol; polyether; polyacrylic acid; polymetharyl acid; polyester; polyolefin; silicone resin; urethane resin; melamine resin; urea resin; and epoxy resin.

[0083] It is desirable to use a polymer material with higher heat resistance than the material of the porous sheet for the resin material contained in the composite material layer (heat-resistant layer). Such a polymer material preferably includes at least one selected from the group consisting of aromatic polyamides, aromatic polyimides, and aromatic polyamide-imides. These are known as polymer materials with high heat resistance. From the viewpoint of heat resistance, aramid, specifically meta-aramid (meta-total aromatic polyamide) and para-aramid (para-total aromatic polyamide), is preferred.

[0084] The inorganic particle content in the composite material layer may be in the range of 50% to 99% by mass (for example, in the range of 85% to 99% by mass).

[0085] The composite material layer is formed, for example, by applying a coating solution containing inorganic particles, a resin material, and a liquid component (dispersion medium) to a porous sheet and drying the coating film. Examples of liquid components include N-methyl-2-pyrrolidone.

[0086] (Spacer) The spacer is formed on the main surface of the substrate. From the viewpoint of facilitating the fabrication of the electrode group, it is preferable that the spacer is integrated with the substrate. The spacer may be provided on the main surface of the substrate facing the positive electrode (the main surface of the substrate on the positive electrode side), on the main surface of the substrate facing the negative electrode (the main surface of the substrate on the negative electrode side), or on both main surfaces. When the spacer is provided on the main surface of the substrate facing the positive electrode, compared to when the spacer is provided on the main surface of the substrate facing the negative electrode, Li precipitates between the spacers in a way that stretches the substrate toward the positive electrode, so compressive stress is generated in the precipitated Li, and Li tends to precipitate densely. From the viewpoint of improving discharge efficiency and cycle characteristics, it is preferable that the spacer is provided on the main surface of the substrate facing the positive electrode. On the other hand, when the spacer is provided on the main surface of the substrate facing the negative electrode, a space is formed in advance between the substrate and the negative electrode, so the tensile load on the substrate that follows the deposition of Li is reduced. In other words, it is advantageous in that it is easier to maintain the insulating properties of the substrate or the short-circuit resistance of the substrate.

[0087] In lithium-ion batteries, the main role of spacers is to create a space for the deposition of lithium metal. The lithium metal is contained within the space provided by the spacers, thereby suppressing volume changes in the electrode group.

[0088] The spacer may contain a resin material (e.g., an insulating resin), or it may contain a resin material and particles. The proportion of resin material in the spacer may be 10% by volume or more, 30% by volume or more, or 50% by volume or more, or it may be 100% by volume or less, or 80% by volume or less.

[0089] Examples of resin materials included in the spacer include fluorine-containing resins such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene, fluorine-containing rubbers such as vinylidene fluoride-tetrafluoroethylene copolymer and ethylene-tetrafluoroethylene copolymer, styrene-butadiene copolymer or its hydride, acrylonitrile-butadiene copolymer or its hydride, methacrylic acid ester-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl alcohol, polyvinyl acetate, and other rubbers. Examples include cellulose derivatives such as ethylcellulose, methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose; acrylic resins such as acrylic acid-metharyl acid copolymers; polyamides such as polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyimide, and fully aromatic polyamides (aramids); polyamideimide; polyacrylonitrile; polyvinyl alcohol; polyether; polyacrylic acid; polymetharyl acid; polyester; polyolefin; silicone resin; urethane resin; melamine resin; urea resin; and epoxy resin.

[0090] From the viewpoint of suppressing the increase in the gas generation reaction rate during internal short circuits, it is preferable that the spacer has a non-porous structure that does not allow lithium ions to permeate. Among the above resin materials, polyimide, polyvinylidene fluoride, and acrylonitrile-acrylic acid ester copolymers are preferred as materials that do not allow lithium ions to permeate, and polyimide may also be used. A non-porous spacer of a certain height or more formed from these resin materials is a layer that does not allow lithium ions to permeate.

[0091] The particles may be inorganic or organic. Among these, inorganic particles such as insulating metal oxides, metal hydroxides, metal nitrides, metal carbides, and metal sulfides are particularly suitable. Preferred metal oxides include aluminum oxide (alumina and boehmite), magnesium oxide, titanium oxide (titania), zirconium oxide, and silicon oxide (silica). Examples of metal hydroxides include aluminum hydroxide. Examples of metal nitrides include silicon nitride, aluminum nitride, boron nitride, and titanium nitride. Examples of metal carbides include silicon carbide and boron carbide. Examples of metal sulfides include barium sulfate. Minerals such as aluminosilicates, layered silicates, barium titanate, and strontium titanate may also be used. Among these, alumina, silica, and titania are particularly preferred.

[0092] The average particle size is not particularly limited, but may be 0.1 μm or larger, 0.5 μm or larger, 10 μm or smaller, 5 μm or smaller, or 2 μm or smaller. The average particle size can be measured by the following method. First, a cross-section of the spacer in the thickness direction of the separator is photographed with an electron microscope to obtain an image of the cross-section. Next, image processing such as binarization is performed on the image to identify the parts of the particles. Next, the diameter of a circle having the same area as the cross-sectional area of ​​each particle (equivalent circle diameter) is determined, and the arithmetic mean of the obtained equivalent circle diameters can be taken as the average particle size. The arithmetic mean can be calculated from, for example, 100 or more particles. The average particle size of other particles contained in the electrode plate and separator can also be determined by the same method.

[0093] When the spacer contains resin material and particles, it is preferable that the particle content in the spacer be 50% by volume or less. This makes it easier to ensure sufficient strength of the spacer.

[0094] The spacer has multiple linear portions (linear protrusions). The height H of the spacer (linear portion) (for example, the height H1 of the first linear portion and the height H2 of the second linear portion) may be greater than the thickness T of the base material. The ratio of height H to thickness T, H / T, is greater than 1 and may be 1.5 or more, 2 or more, or 3 or more. H / T may be 10 or less, 8 or less, 5 or less, or 4 or less. When H / T is 1.5 or more, the expansion of the electrode group is easily suppressed.

[0095] The height H can be measured by the following method. First, a cross-section of the separator (substrate) in the thickness direction is photographed with an electron microscope to obtain an image of the cross-section. Next, 20 arbitrary locations among the spacers are selected from the image, and the height of the spacer at each location is measured. Then, the heights of the 20 measured locations are arithmetic mean, and the resulting average value is taken as the height H. The thickness T can be measured using the same procedure.

[0096] Spacers are formed, for example, by applying a coating solution containing spacer components and liquid components to a predetermined location on a substrate and drying the coating film. Examples of liquid components include N-methyl-2-pyrrolidone. Coating may be done using a dispenser or other known printing methods such as gravure printing, inkjet printing, and screen printing. Drying may be done by known methods such as heating or natural drying.

[0097] The following provides a detailed explanation of the positive electrode, negative electrode, and non-aqueous electrolyte of a secondary battery.

[0098] (Lithium secondary battery) (Negative electrode) The negative electrode is equipped with a negative electrode current collector. The negative electrode may consist only of the negative electrode current collector, or it may include a thin lithium metal foil that has been pre-pressed onto the negative electrode current collector. In a lithium secondary battery, lithium metal is deposited on the surface of the negative electrode by charging. More specifically, lithium ions contained in the non-aqueous electrolyte receive electrons on the negative electrode during charging and become lithium metal, which is deposited on the surface of the negative electrode. The lithium metal deposited on the surface of the negative electrode dissolves as lithium ions in the non-aqueous electrolyte during discharge. The lithium ions contained in the non-aqueous electrolyte may originate from lithium salts added to the non-aqueous electrolyte, or they may be supplied from the positive electrode active material during charging, or both.

[0099] The negative electrode may include a lithium ion storage layer (a layer that exhibits capacity through the absorption and release of lithium ions by the negative electrode active material) supported on the negative electrode current collector. In this case, the open-circuit potential of the negative electrode at full charge may be 70 mV or less relative to the lithium metal (lithium dissolution potential). When the open-circuit potential of the negative electrode at full charge is 70 mV or less relative to the lithium metal, lithium metal is present on the surface of the lithium ion storage layer at full charge. That is, the negative electrode exhibits capacity through the deposition and dissolution of lithium metal.

[0100] Here, "fully charged" refers to the state in which the battery has been charged to a charge level of, for example, 0.98 × C or higher, where C is the rated capacity of the battery. The open-circuit potential of the negative electrode at full charge can be measured by disassembling the fully charged battery under an argon atmosphere, removing the negative electrode, and assembling a cell with lithium metal as the counter electrode. The non-aqueous electrolyte of the cell may have the same composition as the non-aqueous electrolyte in the disassembled battery.

[0101] The lithium-ion storage layer is formed by creating layers of a negative electrode composite material containing a negative electrode active material. In addition to the negative electrode active material, the negative electrode composite material may also contain binders, conductive materials, thickeners, etc.

[0102] Examples of negative electrode active materials include carbonaceous materials, Si-containing materials, and Sn-containing materials. The negative electrode may contain one type of negative electrode active material, or a combination of two or more types. Examples of carbonaceous materials include graphite, easily graphitizable carbon (soft carbon), and difficult-to-graphitize carbon (hard carbon).

[0103] Conductive materials include, for example, carbon materials. Examples of carbon materials include carbon black, acetylene black, Ketjenblack, and carbon nanotubes.

[0104] Examples of binders include fluororesins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubbery polymers. Examples of fluororesins include polytetrafluoroethylene and polyvinylidene fluoride. Examples of thickeners include carboxymethylcellulose and its sodium salt.

[0105] The negative electrode current collector can be any conductive sheet. Examples of conductive sheets include foil and film.

[0106] The material of the negative electrode current collector (conductive sheet) may be any conductive material other than lithium metal and lithium alloys. The conductive material may be a metallic material such as a metal or alloy. Preferably, the conductive material is one that does not react with lithium. More specifically, it is preferable that the conductive material does not form any alloys or intermetallic compounds with lithium. Examples of such conductive materials include copper (Cu), nickel (Ni), iron (Fe), and alloys containing these metallic elements, or graphite in which the basal surface is preferentially exposed. Examples of alloys include copper alloys and stainless steel (SUS). Among these, copper and / or copper alloys with high conductivity are preferred.

[0107] The thickness of the negative electrode current collector is not particularly limited, but is, for example, 5 μm or more and 300 μm or less.

[0108] (Positive electrode) The positive electrode comprises a positive electrode current collector and a positive electrode composite layer supported on the positive electrode current collector. The positive electrode composite layer includes, for example, a positive electrode active material, a conductive material, and a binder. The positive electrode composite layer may be formed on only one side of the positive electrode current collector or on both sides. The positive electrode can be obtained, for example, by applying a positive electrode composite slurry containing the positive electrode active material, a conductive material, and a binder to both sides of the positive electrode current collector, drying the coating, and then rolling it.

[0109] The positive electrode active material is a material that intercepts and releases lithium ions. Examples of positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides. Among these, lithium-containing transition metal oxides are preferred because they have low manufacturing costs and a high average discharge voltage.

[0110] During charging, lithium contained in lithium-containing transition metal oxides is released from the positive electrode as lithium ions and deposited as lithium metal on the negative electrode or negative electrode current collector. During discharge, the lithium metal dissolves from the negative electrode, releasing lithium ions, which are then absorbed into the composite oxide of the positive electrode. In other words, the lithium ions involved in charging and discharging generally originate from the solute in the non-aqueous electrolyte and the positive electrode active material.

[0111] Examples of transition metal elements included in lithium-containing transition metal oxides include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, and W. Lithium-containing transition metal oxides may contain one transition metal element or two or more. The transition metal elements may be Ni, Co, and / or Mn. Lithium-containing transition metal oxides may optionally contain one or more main group elements. Examples of main group elements include Mg, Al, Ca, Zn, Ga, Ge, Sn, Sb, Pb, and Bi. The main group elements may also be Al, etc.

[0112] Among lithium-containing transition metal oxides, composite oxides containing Ni, Co, and / or Mn as transition metal elements, and possibly Al as an optional component, and having a layered rock salt-type crystalline structure, are preferred for obtaining high capacity. In this case, in a lithium secondary battery, the molar ratio of the total amount of lithium (mLi) in the positive and negative electrodes to the amount of metal M other than lithium (mM) in the positive electrode (mLi / mM) is set to, for example, 1.1 or less.

[0113] For example, the binder and conductive materials exemplified for the negative electrode can be used. For the positive electrode, graphite can be used as the conductive material. The shape and thickness of the positive electrode current collector can be selected from the shape and range of the positive electrode current collector.

[0114] Examples of materials for the positive electrode current collector (conductive sheet) include metallic materials containing Al, Ti, Fe, etc. The metallic material may be Al, Al alloy, Ti, Ti alloy, Fe alloy, etc. The Fe alloy may be stainless steel (SUS).

[0115] The thickness of the positive electrode current collector is not particularly limited, but is, for example, 5 μm or more and 300 μm or less.

[0116] (Non-aqueous electrolyte) The non-aqueous electrolyte having lithium ion conductivity may be a liquid electrolyte (electrolyte), a gel electrolyte, or a solid electrolyte. The liquid electrolyte is, for example, an electrolyte containing a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. The concentration of the lithium salt in the electrolyte is, for example, 0.5 mol / L or more and 2 mol / L or less. The electrolyte may contain known additives.

[0117] The gel-like electrolyte comprises a lithium salt and a matrix polymer, or a lithium salt, a non-aqueous solvent, and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, and polyethylene oxide.

[0118] As the solid electrolyte, for example, materials known in all-solid-state lithium ion secondary batteries and the like (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0119] The liquid non-aqueous electrolyte is prepared by dissolving a lithium salt in a non-aqueous solvent. When the lithium salt dissolves in the non-aqueous solvent, lithium ions and anions are generated.

[0120] As the anion, BF － , ４ , ｙ , － , ２ , ２ － , ClO ４ － , PF ６ － , CF ３ SO ３ － , CF ３ CO ２ － , anions of imides, anions of oxalate complexes, etc. are exemplified. As the anion of imides, N(SO ２ CF ３ ), N(C ２ － F ｍ SO ２ｍ＋１ ), N(C ２ F ｘ (C ｎ F ２ｎ＋１ SO ２ (m and n are each independently 0 or an integer of 1 or more, x and y are each independently 0, 1 or 2, and x + y = 2 is satisfied.) etc. are exemplified. The anion of the oxalate complex may contain boron and / or phosphorus. As the anion of the oxalate complex, bisoxalate borate anion, difluorooxalate borate anion (BF ｙ － (C ２ O ２ ), PF ４ (C － O ４ ), PF ２ (C ４ O － ), PF ２ (C ２ O ４ (C ２ －Examples include these. Non-aqueous electrolytes may contain these anions individually or in combination of two or more.

[0121] From the viewpoint of suppressing the dendritic deposition of lithium metal, the non-aqueous electrolyte preferably contains at least an oxalate complex anion, and more preferably an oxalate complex anion containing fluorine. The interaction between the fluorine-containing oxalate complex anion and lithium makes it easier for lithium metal to precipitate uniformly in fine particulate form. Therefore, it is easier to suppress localized deposition of lithium metal. The fluorine-containing oxalate complex anion may be combined with other anions. Other anions include PF ６ － And / or imide anions.

[0122] Examples of non-aqueous solvents include esters, ethers, nitriles, amides, or halogen-substituted compounds thereof. The non-aqueous electrolyte may contain one of these non-aqueous solvents or two or more of them. Examples of halogen-substituted compounds include fluorides.

[0123] Examples of esters include carbonate esters and carboxylic acid esters. Examples of cyclic carbonate esters include ethylene carbonate, propylene carbonate, and fluoroethylene carbonate (FEC). Examples of linear carbonate esters include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate. Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone. Examples of linear carboxylic acid esters include ethyl acetate, methyl propionate, and methyl fluoropropionate.

[0124] Examples of ethers include cyclic ethers and linear ethers. Examples of cyclic ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of linear ethers include 1,2-dimethoxyethane, diethyl ether, ethyl vinyl ether, methylphenyl ether, benzyl ethyl ether, diphenyl ether, dibenzyl ether, 1,2-diethoxyethane, and diethylene glycol dimethyl ether.

[0125] The concentration of lithium salt in the non-aqueous electrolyte is, for example, 0.5 mol / L or more and 3.5 mol / L or less. The concentration of anion in the non-aqueous electrolyte may be 0.5 mol / L or more and 3.5 mol / L or less. Alternatively, the concentration of anion of the oxalate complex in the non-aqueous electrolyte may be 0.05 mol / L or more and 1 mol / L or less.

[0126] The non-aqueous electrolyte may contain additives. The additives may form a film on the negative electrode. The formation of a film derived from the additive on the negative electrode makes it easier to suppress dendrite formation. Examples of such additives include vinylene carbonate, FEC, vinyl ethyl carbonate (VEC), and the like.

[0127] (Lithium-ion battery) The negative electrode of a lithium-ion battery contains a negative electrode active material capable of intercalating and releasing lithium ions. The positive electrode and non-aqueous electrolyte of a lithium-ion battery can be those exemplified in lithium secondary batteries. The positive electrode composite material and positive electrode current collector can be appropriately selected from those exemplified above. The non-aqueous solvent and lithium salt (anion) contained in the non-aqueous electrolyte can be appropriately selected from those exemplified above.

[0128] The negative electrode comprises, for example, a negative electrode current collector and a negative electrode composite material layer (the lithium ion storage layer described above) supported on the negative electrode current collector. The negative electrode composite material layer may be supported on one main surface of the negative electrode current collector, or on both main surfaces of the negative electrode current collector. The negative electrode composite material and the negative electrode current collector can be appropriately selected from those exemplified above.

[0129] In the following, an example of a secondary battery according to this embodiment will be specifically described with reference to the drawings. The components of the secondary battery example described below can be the components described above. Furthermore, the components of the example described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiment. Furthermore, in the secondary battery described below, components that are not essential to the secondary battery according to this disclosure may be omitted. Note that the scale of the components in the following figures has been changed to facilitate understanding.

[0130] Here, Figure 6 is a schematic longitudinal cross-sectional view showing an example of a secondary battery according to the embodiment of this disclosure. In Figure 6, a cylindrical lithium secondary battery is shown as an example of a secondary battery. Note that in Figure 6, the spacers and the spaces formed by the spacers are not shown.

[0131] The cylindrical lithium secondary battery 10 includes a cylindrical battery case and a wound electrode group 14 and a non-aqueous electrolyte (not shown) housed within the battery case. The battery case includes a case body 15, which is a bottomed cylindrical metal container, and a sealing body 16 that seals the opening of the case body 15. A gasket 27 is placed between the case body 15 and the sealing body 16. The gasket 27 ensures that the battery case is airtight. Inside the case body 15, insulating plates 17 and 18 are placed at both ends of the electrode group 14 in the direction of the winding axis, respectively.

[0132] The case body 15 has a stepped portion 21 formed, for example, by partially pressing the side wall of the case body 15 from the outside. The stepped portion 21 may be formed in an annular shape on the side wall of the case body 15 along the circumferential direction of the case body 15. In this case, the sealing body 16 is supported on the opening side surface of the stepped portion 21.

[0133] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26. In the sealing body 16, these members are stacked in this order. The sealing body 16 is fitted into the opening of the case body 15 such that the cap 26 is located on the outside of the case body 15 and the filter 22 is located on the inside of the case body 15. Each of the above-mentioned members constituting the sealing body 16 is, for example, disc-shaped or ring-shaped. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, with the insulating member 24 interposed between their respective peripheries. The filter 22 and the lower valve body 23 are connected to each other at their respective centers. The upper valve body 25 and the cap 26 are connected to each other at their respective centers. In other words, each member except the insulating member 24 is electrically connected to each other.

[0134] The lower valve body 23 has a ventilation hole (not shown) formed therein. Therefore, if the internal pressure of the battery case rises due to abnormal heat generation or the like, the upper valve body 25 bulges towards the cap 26 and separates from the lower valve body 23. This disconnects the electrical connection between the lower valve body 23 and the upper valve body 25. If the internal pressure rises further, the upper valve body 25 ruptures, and gas is discharged through an opening (not shown) formed in the cap 26.

[0135] Figure 7 is an enlarged view of a part of the electrode group 14. Figure 7 includes the portion near the positive electrode enclosed by region II in Figure 6 and the portion near the negative electrode enclosed by region III in Figure 6.

[0136] The electrode group 14 includes a positive electrode 11, a negative electrode 12, and a separator (a base material 50 and a spacer 53). The base material 50 of the positive electrode 11, the negative electrode 12, and the separator are all in the shape of a strip. The electrode group 14 is formed by winding the positive electrode 11, the negative electrode 12, and the separator so that the separator is positioned between the positive electrode 11 and the negative electrode 12. The separator is a separator according to the embodiment of this disclosure (for example, the separator shown in Figures 1 to 5).

[0137] The positive electrode 11 includes a positive electrode current collector 11a and a positive electrode composite layer 11b. The positive electrode current collector 11a is electrically connected to a cap 26, which functions as a positive electrode terminal, via a positive electrode lead 19. In Figure 7, the negative electrode 12 is shown as a negative electrode (negative electrode current collector) in a state where lithium metal has not been deposited. The negative electrode 12 is electrically connected to a case body 15, which functions as a negative electrode terminal, via a negative electrode lead 20.

[0138] The base material 50 has a main surface 50a facing the positive electrode 11 and a main surface 50b facing the negative electrode 12. The base material 50 of Embodiment 1 comprises a porous sheet 51 and a composite material layer 52 (heat-resistant layer). The composite material layer 52 is formed on the main surface of the porous sheet 51 that faces the positive electrode 11. In Embodiment 1, the spacer 53 is formed on the main surface 50a facing the positive electrode 11. The spacer 53 is formed on the composite material layer 52 and is in contact with the positive electrode 11. The spacer 53 creates a space 14s between the positive electrode 11 and the negative electrode 12 (between the negative electrode 12 and the base material 50). Figure 7 shows the height h of the spacer 53.

[0139] In Figure 7, the spacer 53 is positioned on the main surface 50a of the base material 50 on the positive electrode 11 side, but it may also be positioned on the main surface 50b of the base material 50 on the negative electrode 12 side. The spacer 53 is formed on the composite material layer 52, but it may also be formed on the porous sheet 51. The composite material layer 52 of the base material 50 is positioned on the positive electrode 11 side, but it may also be positioned on the negative electrode 12 side.

[0140] In the lithium secondary battery 10, lithium metal is deposited on the negative electrode 12 during charging. Since a space 14s exists between the positive electrode 11 and the negative electrode 12, the volume change of the electrode group 14 due to the deposition of lithium metal is reduced, and the cycle characteristics are improved.

[0141] The secondary battery according to the embodiments of this disclosure is not limited to a cylindrical secondary battery equipped with a wound electrode group. The shape of the secondary battery can be appropriately selected from various shapes such as cylindrical, coin-shaped, prismatic, sheet-shaped, and flattened, depending on its application. The form of the electrode group is also not particularly limited and may be stacked.

[0142] (Note) The above description of embodiments discloses the following technologies. (Technical 1) The device comprises a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode composite layer supported on the positive electrode current collector, the separator includes a sheet-like substrate and a spacer disposed on the main surface of the substrate, the substrate has a long shape with a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction, the substrate has a first region, a second A region and a second B region extending in the second direction, the second A region and the second B region are arranged on both sides in the first direction and overlap with both ends of the positive electrode composite layer in the first direction, the first region is disposed between the second A region and the second B region, the spacer has a plurality of linear portions, the plurality of linear portions are arranged in a stripe shape inclined with respect to the second direction. A secondary battery wherein the spacer is disposed in the first region, and the spacer is not disposed in the second A region and the second B region. (Technical 2) The secondary battery according to Technical 1, wherein the first region includes a first A region and a first B region extending in the second direction, the spacer includes a first spacer and a second spacer, the plurality of linear portions include a plurality of first linear portions and a plurality of second linear portions, the first spacer has the plurality of first linear portions, the second spacer has the plurality of second linear portions, the first spacer is disposed in the first A region, the second spacer is disposed in the first B region, a third region extending in the second direction is formed between the first A region and the first B region, and neither the first spacer nor the second spacer is disposed in the second A region, the second B region and the third region. (Technical 3) The secondary battery according to Technical 2, wherein the plurality of first linear portions and the plurality of second linear portions are inclined in opposite angular directions with respect to the second direction.(Technology 4) The secondary battery according to any one of Techniques 1 to 3, wherein the substrate is arranged on both sides of the first region in the second direction and has a fourth A region and a fourth B region that overlap with both ends of the positive electrode composite layer in the second direction, and the spacer is not arranged in the fourth A region and the fourth B region. (Technology 5) The secondary battery according to any one of Techniques 1 to 4, wherein at least a portion of the plurality of linear portions has one or more defects, and the ratio of the total length of the defects included in one linear portion to the length of one linear portion is 5% or more and 30% or less. (Technology 6) In a plan view of the positive electrode, the ratio of the area of ​​the region in which the positive electrode composite layer faces the first region to the area of ​​the positive electrode composite layer is 50% or more. (Technology 7) The secondary battery according to any one of Techniques 1 to 6, wherein the spacer includes a resin material. (Technology 8) The secondary battery according to any one of Technology 1 to 7, wherein the spacer has a non-porous structure that does not allow lithium ions to pass through. (Technology 9) The secondary battery according to any one of Technology 1 to 8, wherein the negative electrode is an electrode in which lithium metal is deposited during charging and the lithium metal dissolves in the non-aqueous electrolyte during discharge. (Technical 10) A separator for a secondary battery comprising a sheet-like substrate and a spacer disposed on the main surface of the substrate, wherein the substrate has a long shape having a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction, the substrate has a first region, a second A region and a second B region extending in the second direction, the second A region and the second B region are disposed on both sides of the first direction, the first region is disposed between the second A region and the second B region, the spacer has a plurality of linear portions, the plurality of linear portions are arranged in a stripe pattern inclined with respect to the second direction, the spacer is disposed in the first region, and the spacer is not disposed in the second A region and the second B region.(Technical 11) A separator for a secondary battery according to Technical 10, wherein the first region includes a first A region and a first B region extending in the second direction, the spacer includes a first spacer and a second spacer, the plurality of linear portions include a plurality of first linear portions and a plurality of second linear portions, the first spacer has the plurality of first linear portions, the second spacer has the plurality of second linear portions, the first spacer is disposed in the first A region, the second spacer is disposed in the first B region, a third region extending in the second direction is formed between the first A region and the first B region, and neither the first spacer nor the second spacer is disposed in the second A region, the second B region and the third region. (Technical 12) A separator for a secondary battery according to Technical 11, wherein the plurality of first linear portions and the plurality of second linear portions are inclined in opposite angular directions with respect to the second direction. (Technical 13) The substrate has a fourth A region and a fourth B region arranged on both sides in the second direction, the first region is arranged between the fourth A region and the fourth B region, and the spacer is not arranged in the fourth A region and the fourth B region, the separator for a secondary battery according to any one of Technical 10 to 12. (Technical 14) At least a portion of the plurality of linear portions has one or more defects, and the ratio of the total length of the defects included in one linear portion to the length of one linear portion is 5% or more and 30% or less, the separator for a secondary battery according to any one of Technical 10 to 13. (Technical 15) The spacer is made of a resin material, the separator for a secondary battery according to any one of Technical 10 to 14. (Technical 16) The spacer is made of a non-porous structure that does not allow lithium ions to pass through, the separator for a secondary battery according to any one of Technical 10 to 15. (Technical 17) A separator for a secondary battery according to any one of Technical 10 to 16, wherein, in a plan view of the substrate, the ratio of the area of ​​the region in which the substrate faces the spacer to the area of ​​the substrate is 5% or more and 25% or less.

[0143] [Examples] The secondary battery relating to this disclosure will be described in more detail below based on examples and comparative examples. However, this disclosure is not limited to the following examples.

[0144] 《Batteries A1, A2》 (Preparation of positive electrode) A positive electrode slurry was prepared by mixing a positive electrode active material, acetylene black (AB; conductive material), polyvinylidene fluoride (PVdF; binder), and an appropriate amount of N-methyl-2-pyrrolidone (NMP). The positive electrode active material used was a rock salt type lithium-containing transition metal oxide (NCA: positive electrode active material) having a layered structure and containing Li, Ni, Co, and Al (the molar ratio of Li to the total of Ni, Co, and Al is 1.0). In the positive electrode slurry, the mass ratio of NCA:AB:PVdF was set to 95:2.5:2.5. The positive electrode slurry was applied to both sides of a strip-shaped Al foil (positive electrode current collector), the coating was dried, and the material was rolled to form a positive electrode layer. A positive electrode current collector, with positive electrode composite material layers formed on both sides, was cut to a predetermined size to obtain a long positive electrode. A portion of the current collector was exposed near the center in the length direction of the positive electrode, where the positive electrode composite material layer was not supported along the width direction. A positive electrode lead was attached to the exposed current collector portion.

[0145] (Preparation of the negative electrode current collector) A long piece of electrolytic copper foil (12 μm thick) was prepared as the negative electrode current collector. A negative electrode lead was attached to the negative electrode current collector.

[0146] (Preparation of Substrate) A 10 μm thick microporous thin film made of polyethylene was prepared. A coating solution containing paraphenylene terephthalamide, an aromatic polyamide, as a resin material, and alumina as inorganic particles, was applied to one main surface of the microporous thin film. The coating solution was an N-methyl-2-pyrrolidone solution containing 5.8% by mass of calcium chloride, adjusted to a concentration of 2 wt% aromatic polyamide and 4 wt% alumina. The microporous thin film with the coating was left for 1 hour at a temperature of 25°C and a relative humidity of 70% to precipitate the aromatic polyamide. Next, NMP and calcium chloride in the coating were removed by washing with water. A 5 μm thick composite material layer (heat-resistant layer) was formed by drying the coating at 60°C for 5 minutes. In this way, a substrate (15 μm thick) having a microporous thin film and a composite material layer was obtained.

[0147] (Formation of spacers on the main surface of the substrate) A coating solution containing polyvinylidene fluoride and alumina particles (inorganic filler) was applied to the microporous thin film of the substrate described above, and the coating film was dried to form spacers. In this way, a separator shown in Figure 3 or Figure 4 was obtained. A first spacer 53a (first linear portion 63a) and a second spacer 53b (second linear portion 63b) were placed in the first region P1 and the second region P2 of the substrate 50 in Figure 3 or Figure 4, respectively. In battery A1, the separator shown in Figure 3 was used. In battery A2, the separator shown in Figure 4 was used.

[0148] In the separator shown in Figure 3, a first A region P1A, a first B region P1B, a second A region P2A, a second B region P2B, and a third region P3 were formed on the base material 50. A first spacer 53a (a plurality of first linear portions 63a) was placed in the first A region P1A, and a second spacer 53b (a plurality of second linear portions 63b) was placed in the first B region P1B. Neither the first spacer 53a nor the second spacer 53b was placed in the second A region P2A, the second B region P2B, and the third region P3.

[0149] In the separator shown in Figure 4, the base material 50 was formed with a first A region P1A, a first B region P1B, a second A region P2A, a second B region P2B, a third region P3, and a fourth A region P4A. A first spacer 53a (multiple first linear portions 63a) was placed in the first A region P1A, and a second spacer 53b (multiple second linear portions 63b) was placed in the first B region. Neither the first spacer 53a nor the second spacer 53b was placed in the second A region P2A, the second B region P2B, the third region P3, and the fourth A region P4A.

[0150] The width W1A of the first region A P1A and the width W1B of the first region B P1BA were both 8.4 mm. The width W2A of the second region A P2A and the width W2B of the second region B P2B were both 8.1 mm. The width W3 of the third region P3 was 3.0 mm. WE1 and WE2 were within the range of 2 mm or more and 8 mm or less, respectively.

[0151] The first linear section 63a had a width LW1: 0.5 mm, a height H1: 30 μm, a spacing N1: 3.75 mm, and an inclination angle θ1: 30° with respect to the second direction. The width LW2, height H2, spacing N2, and inclination angle θ2 with respect to the second direction of the second linear section 63b were the same as those of the first linear section 63a: width LW1, height H1, spacing N1, and inclination angle θ1 with respect to the second direction. Multiple first linear sections 63a were arranged continuously. Multiple second linear sections 63b were also arranged continuously.

[0152] In battery A1 (separator in Figure 3), the ratio of the area of ​​the substrate facing the spacer to the total area of ​​the substrate in a plan view was within the range of 45% to 50%. In battery A2 (separator in Figure 4), the ratio of the area of ​​the substrate facing the spacer to the total area of ​​the substrate in a plan view was within the range of 40% to 45%.

[0153] (Preparation of non-aqueous electrolyte) 1,2-dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (CHF ２ CF ２ OCH ２ CF ３ A mixed ether solvent containing ) and in a volume ratio of 1:2 was prepared. Lithium bissulfonylimide (LiFSI) was added to the mixed solvent at a concentration of 1 mol / L, and LiBF ２ (C ２ O ４ A liquid non-aqueous electrolyte (ether-based electrolyte) was prepared by dissolving the substance to a concentration of 0.1 mol / L.

[0154] (Battery Assembly) In an inert gas atmosphere, the positive electrode with the positive electrode lead attached and the negative electrode current collector with the negative electrode lead attached were wound in a spiral shape via a separator to create an electrode group. In this way, a wound electrode group with the structure shown in Figure 7 was obtained. At this time, the electrode group was configured such that separators having spacers in the arrangement pattern shown in Figure 3 or Figure 4 were arranged on the inner and outer sides of the positive electrode, respectively. The positional relationship between the linear protrusions (first linear portion and second linear portion) arranged on the inner and outer sides of the positive electrode, respectively, and the positive electrode was as shown in Figure 3 or Figure 4. The separator was positioned so that the main surface on the side of the base material where the spacer was formed faced the positive electrode.

[0155] An electrode group was housed in a bottomed cylindrical case body, and a non-aqueous electrolyte was injected. A sealing body was placed at the opening of the case body via a gasket, sealing the electrode group and non-aqueous electrolyte inside the battery case. In this way, lithium secondary batteries (batteries A1 and A2) with the structure shown in Figure 6 were completed.

[0156] In batteries A1 and A2, in a plan view of the positive electrode, the ratio of the area of ​​the positive electrode composite layer facing the first region P1 to the area of ​​the positive electrode composite layer was within the range of 50% to 70%.

[0157] Battery B1 was manufactured in the same manner as Battery A1, except that the spacers in the arrangement pattern shown in Figure 8 were formed instead of the spacers in the arrangement pattern shown in Figure 3. In the separator of Figure 8, spacers 53 having multiple linear portions 63 were placed in all areas of the base material 50. The second A region P2A, the second B region P2B, and the third region P3 of Figure 3 were not formed. The multiple linear portions 63 were arranged in a stripe pattern with an inclination in the second direction. The width LW, height, spacing N, and inclination angle θ with respect to the second direction of the linear portions 63 were the same as the width LW1, height H1, spacing N1, and inclination angle θ1 with respect to the second direction of the first linear portion 63a of Battery A1.

[0158] [Evaluation] (Charge-discharge cycle test) A charge-discharge cycle test was performed on each of the obtained batteries. In the charge-discharge cycle test, the batteries were charged in a constant temperature chamber at 25°C under the following conditions, then left to rest for 20 minutes, and then discharged under the following conditions.

[0159] (Charging) Constant current charging was performed at a current of 10 mA per unit area (square centimeter) of the electrodes until the battery voltage reached 4.1 V. After that, constant voltage charging was performed at a voltage of 4.1 V until the current value per unit area of ​​the electrodes reached 1 mA.

[0160] (Discharge) A constant current discharge was performed at a current of 10 mA per unit area (square centimeter) of the electrode until the battery voltage reached 3.0 V.

[0161] The above charging and discharging process was repeated as one cycle. When the charging capacity in the m-th cycle was 1% or more greater than the charging capacity in the previous (m-1)-th cycle, it was determined that abnormal charging had occurred due to a minute internal short circuit, and the charge-discharge test was terminated. The number of cycles m at this point was determined as the number of cycles in which the abnormality occurred.

[0162] Furthermore, the ratio of the discharge capacity at cycle 50 to the discharge capacity at cycle 1 was calculated as the capacity retention rate at cycle 50.

[0163] The evaluation results are shown in Table 1. In Table 1, A1 and A2 are examples, and B1 is a comparative example.

[0164]

[0165] Batteries A1 and A2 used separators having a second A region and a second B region, resulting in a delayed abnormality cycle, suppressed internal short circuits, and improved reliability compared to battery B1.

[0166] Batteries A1 and A2 used separators with a third region, resulting in improved fluid circulation of the electrode group and increased capacity retention compared to battery B1.

[0167] Furthermore, in batteries A1 and A2, a separator was used in which the first spacer and the second spacer were arranged mirror-symmetrically to each other via a third region extending in the second direction, thereby suppressing meandering during the transport of the separator.

[0168] The secondary battery of this disclosure can be used in electronic devices such as mobile phones, smartphones, and tablet devices, electric vehicles including hybrid and plug-in hybrid vehicles, and home battery storage systems combined with solar cells.

[0169] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0170] 10: Lithium secondary battery, 11: Positive electrode, 12: Negative electrode, 14: Electrode group, 14s: Space, 15: Case body, 16: Sealing body, 23: Lower valve body, 25: Upper valve body, 50: Substrate, 51: Porous sheet, 52: Composite material layer, 53: Spacer, 53a: First spacer, 53b: Second spacer, 63: Linear part, 63a: First linear part, 63b: Second linear part, 73a: First defect part, 73b: Second defect part

Claims

1. The device comprises a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode current collector and a positive electrode composite layer supported on the positive electrode current collector, the separator includes a sheet-like substrate and a spacer disposed on the main surface of the substrate, the substrate has a long shape with a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction, the substrate has a first region, a second A region and a second B region extending in the second direction, the second A region and the second B region are arranged on both sides in the first direction and overlap with both ends of the positive electrode composite layer in the first direction, the first region is disposed between the second A region and the second B region, the spacer has a plurality of linear portions, the plurality of linear portions are arranged in a stripe pattern inclined with respect to the second direction. A secondary battery in which the spacer is placed in the first region, and the spacer is not placed in the second A region and the second B region.

2. The secondary battery according to claim 1, wherein the first region includes a first A region and a first B region extending in the second direction, the spacer includes a first spacer and a second spacer, the plurality of linear portions include a plurality of first linear portions and a plurality of second linear portions, the first spacer has the plurality of first linear portions, the second spacer has the plurality of second linear portions, the first spacer is disposed in the first A region, the second spacer is disposed in the first B region, a third region extending in the second direction is formed between the first A region and the first B region, and neither the first spacer nor the second spacer is disposed in the second A region, the second B region, and the third region.

3. The secondary battery according to claim 2, wherein the plurality of first linear portions and the plurality of second linear portions are inclined in opposite angular directions with respect to the second direction.

4. The secondary battery according to any one of claims 1 to 3, wherein the substrate is arranged on both sides of the first region in the second direction and has a fourth A region and a fourth B region that overlap with both ends of the positive electrode composite layer in the second direction, and the spacer is not arranged in the fourth A region and the fourth B region.

5. The secondary battery according to any one of claims 1 to 3, wherein at least a portion of the plurality of linear portions has one or more defects, and the ratio of the total length of the defects included in one linear portion to the length of one linear portion is 5% or more and 30% or less.

6. In a plan view of the positive electrode, the ratio of the area of ​​the region where the positive electrode composite material layer faces the first region to the area of ​​the positive electrode composite material layer is 50% or more, as described in claim 2 or 3.

7. The secondary battery according to any one of claims 1 to 3, wherein the spacer comprises a resin material.

8. The secondary battery according to any one of claims 1 to 3, wherein the spacer has a non-porous structure that does not allow lithium ions to pass through.

9. The secondary battery according to any one of claims 1 to 3, wherein the negative electrode is an electrode in which lithium metal is deposited during charging and the lithium metal dissolves in the non-aqueous electrolyte during discharge.

10. A separator for a secondary battery comprising a sheet-like substrate and a spacer disposed on the main surface of the substrate, wherein the substrate has a long shape having a length L1 in a first direction and a length L2 (L1 < L2) in a second direction perpendicular to the first direction, the substrate has a first region, a second A region and a second B region extending in the second direction, the second A region and the second B region are disposed on both sides of the first direction, the first region is disposed between the second A region and the second B region, the spacer has a plurality of linear portions, the plurality of linear portions are arranged in a stripe pattern inclined with respect to the second direction, the spacer is disposed in the first region, and the spacer is not disposed in the second A region and the second B region.

11. The separator for a secondary battery according to claim 10, wherein the first region includes a first A region and a first B region extending in the second direction, the spacer includes a first spacer and a second spacer, the plurality of linear portions include a plurality of first linear portions and a plurality of second linear portions, the first spacer has the plurality of first linear portions, the second spacer has the plurality of second linear portions, the first spacer is disposed in the first A region, the second spacer is disposed in the first B region, a third region extending in the second direction is formed between the first A region and the first B region, and neither the first spacer nor the second spacer is disposed in the second A region, the second B region, and the third region.

12. The separator for a secondary battery according to claim 11, wherein the plurality of first linear portions and the plurality of second linear portions are inclined in opposite angular directions with respect to the second direction.

13. The separator for a secondary battery according to any one of claims 10 to 12, wherein the substrate has a fourth A region and a fourth B region arranged on both sides in the second direction, the first region is arranged between the fourth A region and the fourth B region, and the spacer is not arranged in the fourth A region and the fourth B region.

14. A separator for a secondary battery according to any one of claims 10 to 12, wherein at least a portion of the plurality of linear portions has one or more defective portions, and the ratio of the total length of the defective portions included in one linear portion to the length of one linear portion is 5% or more and 30% or less.

15. The separator for a secondary battery according to any one of claims 10 to 12, wherein the spacer comprises a resin material.

16. The separator for a secondary battery according to any one of claims 10 to 12, wherein the spacer has a non-porous structure that does not allow lithium ions to pass through.

17. In a plan view of the substrate, the ratio of the area of ​​the region in which the substrate faces the spacer to the area of ​​the substrate is 5% or more and 25% or less, according to any one of claims 10 to 12, for a secondary battery separator.

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