Secondary battery and separator for secondary battery

Abstract

This separator for a secondary battery comprises a sheet-like base material, and a spacer disposed on a principal surface of the base material. The base material 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 base material has a first region, a second region, and a third region extending in the second direction, the third region being formed between the first region and the second region in the first direction. The spacer includes a first spacer and a second spacer. The first spacer includes a plurality of first linear parts arranged in a first pattern. The second spacer includes a plurality of second linear parts arranged in a second pattern. The first spacer is disposed in the first region. The second spacer is disposed in the second region. Neither the first spacer nor the second spacer is disposed in the third 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. 2024-170815, 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. The separator is positioned 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] However, the placement of spacers can sometimes reduce the fluid flow between the electrode group.

[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 region and a third region extending in the second direction, the third region The region is formed between the first region and the second region in the first direction, the spacer includes a first spacer and a second spacer, the first spacer has a plurality of first linear portions arranged in a first pattern, the second spacer has a plurality of second linear portions arranged in a second pattern, the first spacer is located in the first region, the second spacer is located in the second region, and neither the first nor the second spacer is located in the third region, relating to a secondary battery.

[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 region and a third region extending in the second direction, the third region being formed between the first region and the second region in the first direction, the spacer comprising a first spacer and a second spacer, the first spacer having a plurality of first linear portions arranged in a first pattern, the second spacer having a plurality of second linear portions arranged in a second pattern, the first spacer being disposed in the first region, the second spacer being disposed in the second region, and neither the first nor the second spacer being disposed in the third region.

[0010] According to this disclosure, it is possible to suppress the decrease in liquid flowability of the electrode group due to the arrangement of spacers.

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

[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 substrate has a first region, a second region, and a third region extending in the second direction. The third region is formed between the first region and the second region in the first direction. The spacer includes a first spacer and a second spacer, the first spacer having a plurality of first linear portions arranged in a first pattern, and the second spacer having a plurality of second linear portions arranged in a second pattern. The first spacer is disposed in the first region, the second spacer is disposed in the second region, and neither the first nor the second spacer is disposed in the third 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 layer supported on the positive electrode current collector.

[0016] 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.

[0017] The first direction is also called the width direction. The second direction is also called the length direction. Matters common to the first spacer and the second spacer may be simply referred to as spacers. Matters common to the first linear part and the second linear part may be simply referred to as linear parts.

[0018] An electrode group is composed of a positive electrode, a negative electrode, and a separator. For example, the electrode group may be formed by laminating or winding a positive electrode, a negative electrode, and a separator (a base material with spacers disposed thereon). The electrode group may be formed by laminating the positive electrode, the negative electrode, and the separator in a zigzag shape. The outer shape of the wound-type electrode group may be cylindrical or elliptical. For the wound-type electrode group, generally, a long positive electrode, a negative electrode, and a separator are used, and the length directions of the positive electrode, the negative electrode, and the separator become the winding direction.

[0019] By providing the third region, the decrease in the liquid circulation property of the electrode group due to the spacer is suppressed, and the decrease in the cycle characteristics (capacity retention rate) due to the decrease in the liquid circulation property is suppressed. By disposing the first spacer and the second spacer in the first region and the second region on both sides of the third region, respectively, the stability of the space formation by the spacer is sufficiently ensured.

[0020] The first region, the second region, and the third region each extend in the second direction, and the third region is formed between the first region and the second region in the first direction, so that the liquid circulation property is likely to be uniformly improved in the entire facing region of the positive electrode and the negative electrode (in the case of a wound-type electrode group, the winding direction), and the effect of improving the liquid circulation property is significantly obtained.

[0021] One first region, second region, or third region may be formed, or two or more may be formed. Two or more third regions may be formed, and the first region and the second region may be alternately formed via the third region. For example, in the first direction, they may be formed in the order of (first region / third region / second region), (first region / third region / second region / third region / first region), etc.

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

[0023] Let the length in the first direction (width of the first region) of one first region be \(W1\), the length in the first direction (width of the second region) of one second region be \(W2\), and the length in the first direction (width of the third region) of one third region be \(W3\). At this time, \(W3 / W1\) may be 0.1 or more and 0.8 or less (or 0.5 or less), may be 0.2 or more and 0.8 or less, or may be 0.2 or more and 0.5 or less. Also, \(W3 / W2\) may be 0.1 or more and 0.8 or less (or 0.5 or less), may be 0.2 or more and 0.8 or less, or may be 0.2 or more and 0.5 or less.

[0024] \(W1 / W2\) 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 \(W1\) and \(W2\) are substantially equal to each other.

[0025] When forming in the order of (the first region / the third region / the second region) in the first direction, the width \(W3\) of the third region may be, for example, 1.0 mm or more, or may be 2.0 mm or more. Also, in this case, \(W3\) may be, for example, 10.0 mm or less, or may be 7.0 mm or less.

[0026] It is preferable that the first spacer (a plurality of first linear portions) and the second spacer (a plurality of second linear portions) are arranged symmetrically with respect to each other via the third region. By arranging the two spacers symmetrically with respect to each other via the third region, the meandering of the separator during the conveyance of the separator by the roll-to-roll method is suppressed, the electrode group can be stably configured, and the reliability of the battery is improved.

[0027] Preferably, the multiple first linear portions are arranged in a stripe pattern inclined with respect to the second direction as a first pattern, and preferably, the multiple second linear portions are arranged in a stripe pattern inclined with respect to the second direction as a second pattern. In this case, the reliability of the electrode group is improved, and the reliability of the battery is improved. Specifically, a separator can be stably placed between the positive electrode and the negative electrode, 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 having a predetermined diameter can be stably obtained. The space formed between the positive and negative electrodes can be stably maintained by the spacer. Multiple spaces formed between adjacent first linear portions (second linear portions) are connected to spaces formed in the third region, which significantly improves liquid flow. In this case, from the viewpoint that meandering during separator transport is significantly suppressed, it is more preferable that the multiple first linear portions and the multiple second linear portions are inclined in opposite angles with respect to the second direction. In this case, the multiple first linear portions and the multiple second linear portions may be inclined at the same angle with respect to the second direction.

[0028] From the viewpoint of ensuring the stability of space formation by spacers, 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 and second regions 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 flow, 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 and second regions 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 and second regions to the area of ​​the positive electrode composite material layer may be, for example, 50% or more, or 80% or less.

[0029] The first spacer has a plurality of first linear sections arranged in a first pattern. A single first linear section may be straight, curved, or have both a straight and a curved portion. Each of the plurality of first linear sections may be straight or curved. The plurality of first linear sections may include one or more straight linear sections and one or more curved linear sections. In the case of stripe-shaped or honeycomb-shaped patterns, each of the plurality of first linear sections is straight. A single first linear section may be arranged continuously or intermittently. Each of the plurality of first linear sections may be arranged continuously or intermittently. The first linear section may include one or more continuously arranged linear sections and one or more intermittently arranged linear sections. Depending on the arrangement pattern, such as a honeycomb shape, some of the plurality of first linear sections may be arranged at an inclination with respect to the second direction. For example, more than half or more or more than two-thirds of the multiple first linear sections may be inclined with respect to the second direction. Alternatively, all of the multiple first linear sections may be arranged inclined with respect to the second direction using a stripe-like arrangement pattern. In this case, the angle θ (acute angle) at which the first linear section is inclined with respect to the second direction is greater than 0° and less than 90°, and may be between 5° and 85°, or between 10° and 70°.

[0030] The first pattern may be, for example, a striped pattern or a mesh pattern. The mesh pattern may be a collection of polygons. An example of a mesh pattern is a shape in which polygons are combined so that they share sides. Polygons include triangles, quadrilaterals, hexagons, etc. Different types of polygons may be combined. The part that forms one side of the polygon is defined as one first linear part. The mesh pattern may also be honeycomb-shaped.

[0031] The second spacer has a plurality of second linear portions arranged in the second pattern. The same applies to the second spacer and the second linear portions as to the first spacer and the first linear portion. The second pattern can be the pattern exemplified in the first pattern. The plurality of second linear portions can be arranged in the same way as the plurality of first linear portions. The first pattern may be of a different type from the second pattern, but it is preferable that the patterns be of the same type. From the viewpoint of uniformity of the surface pressure of the electrode group, it is preferable that the first linear portions have approximately the same height as the second linear portions. The first linear portions may have a different width dimension from the second linear portions, but from a similar viewpoint, it is preferable that they have approximately the same width.

[0032] It is preferable not to place spacers in the third region, but to the extent that liquid flow is not impaired, several small, dot-shaped spacers (protrusions) may be dispersed in the third region. The ratio of the area of ​​the dot-shaped spacers placed in the third region to the area of ​​the third region is, for example, 3% or less or 2% or less.

[0033] 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. 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). Note that the separators of this disclosure are not limited to these. A space 14s is formed between the positive and negative electrodes by the spacer 53.

[0034] The separator comprises a sheet-like base material 50 and a spacer 53 disposed on one main surface of the base material 50. The spacer 53 has a plurality of linear portions 63. 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 region P2, and a third region P3 extending in the second direction. The third region P3 is formed between the first region P1 and the second region P2 in the first 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 arranged in a first pattern. The second spacer 53b has a plurality of second linear portions 63b arranged in a second pattern. In the first region P1, the first spacer 53a is arranged; in the second region P2, the second spacer 53b is arranged; and in the third region P3, neither the first spacer 53a nor the second spacer 53b is arranged.

[0035] In Figures 1 to 5, the width W1 of the first region P1 and the width W2 of the second region P2 are approximately equal to each other, and may be 5 mm or more and 20 mm or less, respectively. 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. Also, the width W3 of the third region P3 may be 10 mm or less, or 7 mm or less. For example, the width W3 of the third region P3 may be 1 mm or more and 10 mm or less (or 5 mm or less), 2 mm or more and 10 mm or less, or 2 mm or more and 7 mm or less. W3 / W1 and W3 / W2 may be 0.1 or more and 0.8 or less (or 0.5 or less), or 0.2 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.

[0036] The first and second patterns are stripe-shaped patterns inclined with respect to the second direction. That is, the multiple first linear portions 63a are arranged in a stripe shape inclined with respect to the second direction. The 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. The multiple second linear portions 63b are arranged in a stripe shape inclined with respect to the second direction. The 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.

[0037] In Figure 1, the multiple first linear portions 63a and the multiple second linear portions 63b are inclined toward each other in the same angular direction.

[0038] In Figures 2 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 and are arranged mirror-symmetrically with respect to the third region P3. In Figures 2 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 located at approximately the same position in the first direction (D1 direction), but they may be located at different positions in the first direction (D1 direction).

[0039] 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.

[0040] 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.

[0041] In Figures 1 to 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 W1 of the first linear portion is approximately the same as the width W2 of the second linear portion.

[0042] In Figures 2 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.

[0043] (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

[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] In the case of Figures 1-2, the 4A and 4B regions described later are not present. The spacer 53 is positioned to overlap with both ends E1 and E2 of the positive electrode 11 (positive electrode composite layer 11b) in the first direction. Specifically, the first spacer 53a is positioned to overlap with one end E1 of the positive electrode 11 (positive electrode composite layer 11b) in the first direction. The first spacer 53a extends to the end of the base material 50 on the end E1 side of the positive electrode 11. The second spacer 53b is positioned to overlap with the other end E2 of the positive electrode 11 (positive electrode composite layer 11b) in the first direction. The second spacer 53b extends to the end of the base material 50 on the end E2 side of the positive electrode 11.

[0046] In Figures 3 to 5, the spacers 53 are positioned so as not to overlap with the ends E3 and E4 of the positive electrode 11 (positive electrode composite layer 11b) in the first direction. Specifically, in Figures 3 to 5, the first spacer 53a is positioned so as not to overlap with one end E2 of the positive electrode 11 (positive electrode composite layer 11b) in the first direction. The second spacer 53b is positioned so as not to overlap with the other end E2 of the positive electrode 11 (positive electrode composite layer 11b) in the first direction.

[0047] In Figures 3 to 5, the base material 50 has a fourth A region P4A located on one end side in the first direction of the base material 50, which overlaps with one end E1 of the positive electrode composite layer 11b in the first direction. The base material 50 has a fourth B region P4B located on the other end side in the first direction of the base material 50, which overlaps with the other end E2 of the positive electrode composite layer 11b in the first direction. The fourth A region P4A is located on the opposite side of the first region P1 from the third region P3 in the first direction. The fourth B region P4B is located on the opposite side of the second region P2 from the third region P3 in the first direction. Neither the first spacer 53a nor the second spacer 53b is located in the fourth A region P4A or the fourth B region P4B.

[0048] In the case of a pattern in which multiple linear sections are arranged in a stripe shape at an angle to the second direction, many overlapping points are formed where the multiple linear sections intersect with the ends of the positive electrode composite layer in the first direction. Near these overlapping points, stress on the substrate can concentrate locally, which can damage the substrate and cause internal short circuits. Stress is particularly likely to concentrate near the side of the overlapping point that forms an acute angle with respect to the second direction of the linear section (for example, part P of the substrate 50 in Figure 8).

[0049] The first end of the positive electrode faces the end of the Li deposition region (Li ion storage region) of the negative electrode. For example, during charging, Li ions released from the positive electrode move to the negative electrode by wrapping around the spacer (protrusion), and the negative electrode expands due to Li deposition (Li ion storage). As a result, the stress on the substrate may locally increase near the overlapping portion between the first end of the positive electrode and the spacer due to the expansion of the negative electrode. In particular, in lithium secondary batteries, the edge portion of deposited Li tends to form thickly near the overlapping portion between the first end of the positive electrode and the spacer, and the stress on the substrate tends to locally increase due to Li deposition. Also, the positive electrode composite layer is slightly shorter in width than the negative electrode composite layer, and the positive electrode is thicker than the negative electrode. In the vicinity of the overlapping areas mentioned above, the influence of the thickness change (step) that occurs at the boundary between the part of the substrate facing the positive electrode and the part that does not face the positive electrode is significant, which can lead to locally increased stress on the substrate.

[0050] To address this, by forming the 4A and 4B regions as described above, the spacer can be positioned so that it does not overlap with the ends of the positive electrode composite layer in the first direction, thereby suppressing the concentration of stress described above. As a result, damage to the substrate and the resulting internal short circuit can be suppressed. In particular, near the side that forms an acute angle with respect to the second direction of the linear portion (for example, part P of the substrate 50 in Figure 8), the stress applied to the substrate tends to become locally large, so the effect of suppressing the concentration of stress described above is particularly noticeable.

[0051] The 4A region P4A is formed on one end side of the base material 50 in the first direction (the end E1 side of the positive electrode 11), and the length of the 4A region P4A in the first direction (the width of the 4A region P4A) W4A can also be said to be the distance from one of the two sides of the rectangular base material 50 extending in the second direction in a plan view. The 4B region P4B is formed on the other end side of the base material 50 in the first direction (the end E2 side of the positive electrode 11), and the length of the 4B region P4B in the first direction (the width of the 4B region P4B) W4B can also be said to be the distance from the other side of the two sides of the rectangular base material 50 extending in the second direction in a plan view.

[0052] In Figures 3 to 5, the lengths of the 4A and 4B regions in the first direction (widths of the 4A and 4B regions) W4A and W4B are not particularly limited and can be appropriately determined within a range where the 4A and 4B regions and both ends E1 and E2 of the positive electrode composite layer 11b 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 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 50 in the first direction is 60 mm or less, W4A and W4B may be 2.5 mm or more, L1 × 0.25 mm or less, or L1 × 0.25 mm, respectively. If the length L1 of the base material 50 in the first direction is greater than 60 mm, W4A and W4B may be 2.5 mm or more and 15 mm or less, respectively.

[0053] The regions of the 4A region P4A and the 4B region P4B that overlap with the ends E1 and E2 of the positive electrode composite layer 11b in the first direction are regions with a certain width extending in the second direction. For example, in Figure 3, the region of the 4A region P4A facing the end E1 of the positive electrode composite layer 11b in the first direction (D1 direction) is a region with a width WE1 extending in the second direction (D2 direction). The region of the 4B region P4B facing the end E2 of the positive electrode composite layer 11b in the first direction (D1 direction) is a region with a width WE2 extending in the second direction (D2 direction). WE1 and WE2 may be, for example, 2 mm or more and 15 mm or less (or 12 mm or less), respectively. The 4A region P4A and the 4B region P4B in Figures 4 and 5 may also have similar widths.

[0054] Furthermore, in Figure 4, the first spacer 53a and the second spacer 53b are arranged so as not to overlap with one end E3 in the second direction of the positive electrode 11 (positive electrode composite layer 11b). The base material 50 has a fifth A region P5A located on one end side in the second direction of the base material 50, which overlaps with one end E3 in the second direction of the positive electrode composite layer 11b. Neither the first spacer 53a nor the second spacer 53b are arranged in the fifth A region P5A.

[0055] In Figure 5, the first spacer 53a and the second spacer 53b are arranged so as not to overlap with the ends E3 and E4 of the positive electrode 11 (positive electrode composite layer 11b) in the second direction. The base material 50 has a fifth A region P5A located on one end side in the second direction of the base material 50 that overlaps with one end E3 of the positive electrode composite layer 11b in the second direction, and a fifth A region P5A located on the other end side in the second direction of the base material 50 that overlaps with the other end E4 of the positive electrode composite layer 11b in the second direction. Neither the first spacer 53a nor the second spacer 53b are placed in the fifth A region P5A or the fifth B region P5B.

[0056] 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.

[0057] Near the point where the end of the positive electrode (positive electrode composite layer) in the second direction overlaps with the spacer (linear portion), stress on the base material can concentrate locally, similar to the above, potentially damaging the base material and causing an internal short circuit. Damage to the base material can be suppressed by arranging the spacer (linear portion) so as not to overlap with the end E3 (or ends E3, E4) of the positive electrode (positive electrode composite layer) in the second direction, as shown in the separators of Figures 4-5. Since stress concentration is particularly likely to occur at the winding start end, it is even more preferable to arrange the spacer so as not to overlap with the winding start end of the positive electrode.

[0058] The 5A region P5A is formed on one end side of the base material 50 in the second direction, and the length W5A of the 5A region P5A in the second direction can also be said to be the distance from one of the two sides of the rectangular base material 50 extending in the first direction in a plan view. The 5B region P5B is formed on the other end side of the base material 50 in the second direction, and the length W5B of the 4B region in the second direction can also be said to be the distance from the other side of the two sides of the rectangular base material extending in the first direction in a plan view.

[0059] The lengths W5A and W5B in the second direction of region 5A and region 5B are not particularly limited. If the length L2 of the base material 50 in the second direction is 1500 mm or less, W5A and W5B 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 base material 50 in the second direction is greater than 1500 mm, W5A and W5B may be 2.0 mm or more (or 2.5 mm or more) and 15 mm or less, respectively.

[0060] The regions where the 5A region and the 5B region overlap with both ends of the positive electrode composite layer in the second direction are regions with a certain width extending in the first direction. For example, in Figure 5, the region of the 5A region P5A facing the end E3 of the positive electrode composite layer 11b in the second direction (D2 direction) is a region with a width WE3 extending in the first direction (D1 direction). The region of the 5B region P5B facing the end E4 of the positive electrode composite layer 11b in the second direction (D2 direction) is a region with a width WE4 extending in the first direction (D1 direction). WE3 and WE4 may be, for example, 2 mm or more and 15 mm or less (or 12 mm or less).

[0061] The ratio of the area of ​​the region where the positive electrode composite layer 11b faces the first region P1 and the second region P2 to the total area of ​​the positive electrode composite layer 11b may be 50% or more, or 50% or more and 80% or less.

[0062] 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. The length of one first 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.

[0063] 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. 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.

[0064] 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.

[0065] A positive electrode in which a positive electrode mixture layer is supported on one main surface of a 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 mixture layer is supported. Alternatively, a positive electrode in which a positive electrode mixture layer is supported on both main surfaces of a 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).

[0066] (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.

[0067] (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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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).

[0076] 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.

[0077] (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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] The spacer includes at least linear protrusions (linear portions), and may also include a small amount of dot-shaped protrusions, to the extent that it does not impair the effect of suppressing the reduction in liquid flowability by the third region. The linear protrusions (linear portions) are the first linear portion and the second linear portion that constitute the first spacer and the second spacer.

[0086] The linear protrusions (linear parts) may be arranged in a stripe pattern or in a mesh pattern. The mesh pattern may be a collection of polygons. An example of a mesh pattern is a shape in which polygons are combined so that they share sides. Polygons include triangles, quadrilaterals, hexagons, etc. Different types of polygons may be combined. The mesh pattern may be honeycomb-shaped. In addition, the dot-shaped protrusions may be arranged in a predetermined repeating pattern.

[0087] 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, may be greater than 1 and be 1.5 or greater, 2 or greater, or 3 or greater. H / T may be 10 or less, 8 or less, 5 or less, or 4 or less. When H / T is 1.5 or greater, the expansion of the electrode group is easily suppressed.

[0088] 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.

[0089] 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.

[0090] The following provides a detailed explanation of the positive electrode, negative electrode, and non-aqueous electrolyte of a secondary battery.

[0091] (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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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).

[0096] Conductive materials include, for example, carbon materials. Examples of carbon materials include carbon black, acetylene black, Ketjenblack, and carbon nanotubes.

[0097] 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.

[0098] The negative electrode current collector can be any conductive sheet. Examples of conductive sheets include foil and film.

[0099] 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.

[0100] 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.

[0101] (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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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).

[0108] 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.

[0109] (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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] As the anion, BF ４ － , ClO ４ － , PF ６ － , CF ３ SO ３ － , CF ３ CO ２ － , anions of imides, anions of oxalate complexes, etc. are exemplified. As the anions 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 an integer of 0 or 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 [[ID=5)]] － 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.

[0114] 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.

[0115] Examples of non-aqueous solvents include esters, ethers, nitriles, amides, or halogen-substituted versions thereof. The non-aqueous electrolyte may contain one of these non-aqueous solvents or two or more of them. Examples of halogen-substituted versions include fluorides.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] (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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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).

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] (Note) The above description of embodiments discloses the following technologies. (Technical 1) 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 region and a third region extending in the second direction, the third region is formed between the first region and the second region in the first direction, the spacer includes a first spacer and a second spacer, the first spacer has a plurality of first linear portions arranged in a first pattern, the second spacer has a plurality of second linear portions arranged in a second pattern, the first spacer is disposed in the first region, (Technology 2) A secondary battery in which the second spacer is located in the second region, and neither the first spacer nor the second spacer is located in the third region. (Technology 3) A secondary battery according to Technology 1, wherein the first spacer and the second spacer are located mirror-symmetrically to each other across the third region. (Technology 4) A secondary battery according to any one of Technology 1 to 3, wherein the first spacer and the second spacer are located mirror-symmetrically to each other across the third region. (Technical 5) The secondary battery according to any one of Technical 1 to 4, wherein the first spacer and the second spacer are each arranged so as not to face both ends of the positive electrode composite layer in the second direction.(Technology 6) A secondary battery according to any one of Technologies 1 to 5, wherein at least a portion of the plurality of first linear portions has one or more first defects. (Technology 7) A secondary battery according to Technology 6, wherein the ratio of the total length of the first defects included in one first linear portion to the length of one first linear portion is 5% or more and 30% or less. (Technology 8) A secondary battery according to any one of Technologies 1 to 7, wherein at least a portion of the plurality of second linear portions has one or more second defects. (Technology 9) A secondary battery according to Technology 8, wherein the ratio of the total length of the second defects included in one second linear portion to the length of one second linear portion is 5% or more and 30% or less. (Technology 10) A secondary battery according to any one of Technologies 1 to 9, wherein the spacer includes a resin material. (Technology 11) A secondary battery according to any one of Technologies 1 to 10, wherein the spacer has a non-porous structure that does not allow lithium ions to permeate. (Technical 12) A secondary battery according to any one of Technical 1 to 11, wherein, in a plan view of the positive electrode, the ratio of the area of ​​the region in which the positive electrode composite material layer faces the first region and the second region to the area of ​​the positive electrode composite material layer is 50% or more. (Technical 13) A secondary battery according to any one of Technical 1 to 12, 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 14) 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 region and a third region extending in the second direction, the third region is formed between the first region and the second region in the first direction, the spacer comprises a first spacer and a second spacer, the first spacer has a plurality of first linear portions arranged in a first pattern, the second spacer has a plurality of second linear portions arranged in a second pattern, the first spacer is disposed in the first region, the second spacer is disposed in the second region, and neither the first spacer nor the second spacer is disposed in the third region. (Technical 15) A separator for a secondary battery according to Technical 14, wherein the first spacer and the second spacer are arranged mirror-symmetrically with respect to a third region. (Technical 16) A separator for a secondary battery according to Technical 14 or 15, wherein the plurality of first linear portions are arranged in a stripe pattern inclined with respect to the second direction as the first pattern, the plurality of second linear portions are arranged in a stripe pattern inclined with respect to the second direction as the second pattern, and 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 17) A separator for a secondary battery according to any one of Technical 14 to 16, wherein at least a portion of the plurality of first linear portions has one or more first defects. (Technical 18) A separator for a secondary battery according to Technical 17, wherein the ratio of the total length of the first defects included in one first linear portion to the length of one first linear portion is 5% or more and 30% or less. (Technical 19) A separator for a secondary battery according to any one of the technical 14 to 18, wherein at least a portion of the plurality of second linear portions has one or more second defective portions.(Technical 20) The separator for a secondary battery according to Technical 19, wherein the ratio of the total length of the second defect portion contained in one second linear portion to the length of one second linear portion is 5% or more and 30% or less. (Technical 21) The separator for a secondary battery according to any one of Technical 14 to 20, wherein the spacer includes a resin material. (Technical 22) The separator for a secondary battery according to any one of Technical 14 to 21, wherein the spacer has a non-porous structure that does not allow lithium ions to pass through. (Technical 23) The separator for a secondary battery according to any one of Technical 14 to 20, wherein, 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 is 5% or more and 25% or less.

[0136] [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.

[0137] 《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.

[0138] (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.

[0139] (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.

[0140] (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.

[0141] In the separator shown in Figure 3, a first region P1, a second region P2, a third region P3, a fourth A region P4A, and a fourth B region P4B were formed on the base material 50. A first spacer 53a (a plurality of first linear portions 63a) was placed in the first region P1, and a second spacer 53b (a plurality of second linear portions 63b) was placed in the second region P2. Neither the first spacer 53a nor the second spacer 53b was placed in the third region P3, the fourth A region P4A, and the fourth B region P4B.

[0142] In the separator shown in Figure 4, a first region P1, a second region P2, a third region P3, a fourth A region P4A, a fourth B region P4B, and a fifth A region P5A were formed on the base material 50. A first spacer 53a (multiple first linear portions 63a) was placed in the first region P1, and a second spacer 53b (multiple second linear portions 63b) was placed in the second region P2. Neither the first spacer 53a nor the second spacer 53b was placed in the third region P3, the fourth A region P4A, the fourth B region P4B, and the fifth A region P5A.

[0143] The widths W1 of the first region P1 and W2 of the second region P2 were 8.4 mm, respectively. The widths W4A of the fourth region A P4A and W4B of the fourth region B P4B were 8.1 mm, respectively. 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.

[0144] 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.

[0145] 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%.

[0146] (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 ３A 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.

[0147] (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.

[0148] 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.

[0149] 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 and the second region P2 to the total area of ​​the positive electrode composite layer was within the range of 50% to 70%.

[0150] 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 third area P3, the fourth A area P4A, and the fourth B area P4B 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 of the linear portions 63 with respect to the second direction were the same as the width LW1, height H1, spacing N1, and inclination angle θ1 of the first linear portion 63a of Battery A1.

[0151] [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.

[0152] (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.

[0153] (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.

[0154] 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.

[0155] 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.

[0156] The evaluation results are shown in Table 1. In Table 1, A1 and A2 are examples, and B1 is a comparative example.

[0157]

[0158] In batteries A1 and A2, a separator with a third region was used, resulting in improved fluid circulation of the electrode group and increased capacity retention compared to battery B1. Furthermore, in batteries A1 and A2, the overlap between the edges of the positive electrode composite layer and the spacer was reduced, resulting in a delayed abnormality cycle and suppression of minute internal short circuits compared to battery B1.

[0159] Furthermore, in batteries A1 and A2, a separator was used in which a first spacer and a second spacer, which are striped and inclined with respect to the second direction via a third region, are arranged mirror-symmetrically to each other. As a result, meandering during the transport of the separator was suppressed, and the reliability of the battery was improved.

[0160] 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.

[0161] 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.

[0162] 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 region and a third region extending in the second direction, the third region is formed between the first region and the second region in the first direction, the spacer includes a first spacer and a second spacer, the first spacer has a plurality of first linear portions arranged in a first pattern, the second spacer has a plurality of second linear portions arranged in a second pattern, and the first spacer is disposed in the first region. A secondary battery in which the second spacer is located in the second region, and neither the first spacer nor the second spacer is located in the third region.

2. The secondary battery according to claim 1, wherein the first spacer and the second spacer are arranged mirror-symmetrically with respect to each other via a third region.

3. The secondary battery according to claim 2, wherein the plurality of first linear portions are arranged in a stripe pattern inclined with respect to the second direction as the first pattern, the plurality of second linear portions are arranged in a stripe pattern inclined with respect to the second direction as the second pattern, and 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 first spacer and the second spacer are each arranged so as not to face both ends of the positive electrode composite layer in the first direction.

5. The secondary battery according to any one of claims 1 to 3, wherein the first spacer and the second spacer are each arranged so as not to face both ends of the positive electrode composite layer in the second direction.

6. The secondary battery according to any one of claims 1 to 3, wherein at least a portion of the plurality of first linear portions has one or more first defective portions.

7. The secondary battery according to claim 6, wherein the ratio of the total length of the first defect portion contained in one first linear portion to the length of one first linear portion is 5% or more and 30% or less.

8. The secondary battery according to any one of claims 1 to 3, wherein at least a portion of the plurality of second linear portions has one or more second defective portions.

9. The secondary battery according to claim 8, wherein the ratio of the total length of the second defect portion contained in one second linear portion to the length of one second linear portion is 5% or more and 30% or less.

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

11. 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.

12. 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 and the second region to the area of ​​the positive electrode composite material layer is 50% or more, as described in any one of claims 1 to 3.

13. 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.

14. 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 region and a third region extending in the second direction, the third region is formed between the first region and the second region in the first direction, the spacer comprises a first spacer and a second spacer, the first spacer has a plurality of first linear portions arranged in a first pattern, the second spacer has a plurality of second linear portions arranged in a second pattern, the first spacer is disposed in the first region, the second spacer is disposed in the second region, and neither the first spacer nor the second spacer is disposed in the third region.

15. The separator for a secondary battery according to claim 14, wherein the first spacer and the second spacer are arranged mirror-symmetrically with respect to each other via a third region.

16. The separator for a secondary battery according to claim 15, wherein the plurality of first linear portions are arranged in a stripe pattern inclined with respect to the second direction as the first pattern, the plurality of second linear portions are arranged in a stripe pattern inclined with respect to the second direction as the second pattern, and 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.

17. The separator for a secondary battery according to any one of claims 14 to 16, wherein at least a portion of the plurality of first linear portions has one or more first defective portions.

18. The separator for a secondary battery according to claim 17, wherein the ratio of the total length of the first defect portion contained in one first linear portion to the length of one first linear portion is 5% or more and 30% or less.

19. The separator for a secondary battery according to any one of claims 14 to 16, wherein at least a portion of the plurality of second linear portions has one or more second defective portions.

20. The separator for a secondary battery according to claim 19, wherein the ratio of the total length of the second defect portion contained in one second linear portion to the length of one second linear portion is 5% or more and 30% or less.

21. The separator for a secondary battery according to any one of claims 14 to 16, wherein the spacer comprises a resin material.

22. The separator for a secondary battery according to any one of claims 14 to 16, wherein the spacer has a non-porous structure that does not allow lithium ions to pass through.

23. 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 14 to 16, the separator for a secondary battery.

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