Non-aqueous electrolyte secondary battery

Abstract

The present invention relates to a nonaqueous electrolyte secondary battery. According to the present disclosure, a nonaqueous electrolyte secondary battery is provided in which the capacity ratio of the positive electrode to the negative electrode is good and the liquid injection property is improved. The nonaqueous electrolyte secondary battery disclosed herein has an electrode body including a positive electrode, a negative electrode, and a separator, the positive electrode including positive electrode active material layers formed on both faces of a positive electrode core, and the negative electrode including negative electrode active material layers formed on both faces of a negative electrode core. The negative electrode active material layer has a first region between an end edge and a position 5 mm from the end edge in the width direction, and the end portion of the positive electrode opposes at least a portion of the first region. In the thickness of the negative electrode active material layer, the thickness T1 of the central portion of the positive electrode and the thickness T2 of the end portion of the positive electrode satisfy 0.95 < T2 / T1 < 1.05, and in the negative electrode active material layer, the weight per unit area M1 of the central portion of the negative electrode and the weight per unit area M2 of the region of the first region that opposes the positive electrode active material layer satisfy 0.95 < M2 / M1 < 1.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a nonaqueous electrolyte secondary battery. BACKGROUND

[0002] A battery such as a lithium ion secondary battery generally has an electrode body in which a negative electrode and a positive electrode are layered with a separator. As an example of the structure of the electrode body, a structure in which positive electrode tabs and negative electrode tabs for collecting current are provided in the electrode body, and the tabs are electrically connected to a current collecting member is known. For example, Patent Literature 1 discloses a structure in which a positive electrode tab is provided at one end portion of the electrode body, and a negative electrode tab is provided at the other end portion.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2021-060010 SUMMARY

[0006] However, in the production of a battery, it is desirable to shorten the time for injecting an electrolyte into the electrode body. For example, if the density of an active material layer included in an electrode is increased for high capacity, the electrolyte is difficult to penetrate into the inside of the electrode body, and the injection property deteriorates.

[0007] In addition, when the capacities of the positive electrode and the negative electrode are compared, in the case where the capacity of the negative electrode is not enough, charge carriers (for example, lithium ions) are deposited, and it can lead to deterioration of the performance of the battery. Such deposition can also occur when the balance of the capacity ratio (relative capacity ratio) of the opposite positive electrode and negative electrode in a predetermined region is destroyed. Therefore, it is desirable to adjust the balance of the relative capacity ratio in such a manner that the capacity of the negative electrode is not lower than the capacity of the opposite positive electrode in any region.

[0008] Therefore, the present disclosure was completed in view of the above circumstances, and the main object is to provide a nonaqueous electrolyte secondary battery in which the balance of the capacity ratio of the opposite positive electrode and negative electrode is good, and the injection property is improved.

[0009] SOLUTION TO THE PROBLEM

[0010] According to the present disclosure, there is provided a nonaqueous electrolyte secondary battery including an electrode body including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. In the nonaqueous electrolyte secondary battery disclosed herein, the positive electrode includes a positive electrode core and positive electrode active material layers formed on both faces of the positive electrode core, and the negative electrode includes a negative electrode core and negative electrode active material layers formed on both faces of the negative electrode core. A negative electrode tab composed of a portion of the negative electrode core and protruding from one end edge in the width direction of the negative electrode is provided. The negative electrode active material layer has a first region between the end edge and a position 5 mm from the end edge in the width direction of the negative electrode. The end portion of the positive electrode opposes at least a portion of the first region via the separator. The thickness T1 of the positive electrode active material layer at the central portion of the positive electrode and the thickness T2 of the positive electrode active material layer at the end portion of the positive electrode satisfy the relationship 0.95 < T2 / T1 < 1.05. The weight per unit area of the negative electrode active material layer at the central portion of the negative electrode (the mass of the negative electrode active material layer per unit area) M1 and the weight per unit area of the negative electrode active material layer at the region of the first region that opposes the positive electrode active material layer (the mass of the negative electrode active material layer per unit area) M2 satisfy the following condition:

[0011] 0.95 < M2 / M1 < 1.

[0012] According to this structure, the weight per unit area M2 of the negative electrode active material layer at the region of the first region that opposes the positive electrode active material layer is smaller than the weight per unit area M1 of the negative electrode active material layer at the central portion of the negative electrode. Thus, the nonaqueous electrolyte solution easily penetrates from the first region side into the interior of the electrode body, and therefore the liquid injection property is improved. In addition, by causing the weight per unit area M2 of the negative electrode active material layer at the region of the first region that opposes the positive electrode active material layer to satisfy the above condition, even in this region, the charge carriers (for example, lithium ions) from the positive electrode active material layer that opposes the negative electrode active material layer can be sufficiently accommodated (that is, the capacity ratio is well balanced), and therefore the precipitation of the charge carriers can be suppressed.

[0013] In one technical solution of the nonaqueous electrolyte secondary battery disclosed herein, in the first region, the negative electrode active material layer is formed in such a manner that the thickness of the negative electrode active material layer gradually decreases toward the end edge. Thus, an inclined portion is formed in the first region, and therefore a gap is generated between the negative electrode active material layer and the separator, and the liquid injection property is further improved.

[0014] In one technical solution of the nonaqueous electrolyte secondary battery disclosed herein, the positive electrode can have a positive electrode tab composed of a portion of the positive electrode core, and the electrode body can have a plurality of negative electrode tabs at one end portion and a plurality of positive electrode tabs at the other end portion.

[0015] In one aspect of the nonaqueous electrolyte secondary battery disclosed herein, the electrode body can be a jelly-roll electrode body in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound with the strip-shaped separator interposed therebetween. In one aspect of the nonaqueous electrolyte secondary battery disclosed herein, the width of the negative active material layer in the winding axis direction of the jelly-roll electrode body can be 20 cm or more.

[0016] In one aspect of the nonaqueous electrolyte secondary battery disclosed herein, the electrode body can be a jelly-roll electrode body in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound with the strip-shaped separator interposed therebetween. In one aspect of the nonaqueous electrolyte secondary battery disclosed herein, the width of the negative active material layer in the winding axis direction of the jelly-roll electrode body can be 20 cm or more.

[0017] In one aspect of the nonaqueous electrolyte secondary battery disclosed herein, the separator can have an adhesive layer on both surfaces. If a separator having an adhesive layer is used, the shift of the electrode plate during the manufacture of the electrode body can be suppressed, but on the other hand, the liquid injection property is deteriorated. However, according to the structure of the nonaqueous electrolyte secondary battery disclosed herein, the weight per unit area of the end portion vicinity (first region) of the negative active material layer is small, and therefore the adhesion of the adhesive layer to the negative active material layer is weak in the end portion vicinity. In particular, when a slanted portion is formed at the end portion of the negative active material layer, the adhesive layer becomes more difficult to adhere to the slanted portion, and the adhesion becomes weaker or does not adhere to the slanted portion, so that the nonaqueous electrolyte solution easily enters the negative active material layer, and the liquid injection property is improved.

[0018] In one aspect of the nonaqueous electrolyte secondary battery disclosed herein, the negative active material layer can be formed on the negative tab so as to protrude from the end portion of the separator in the protruding direction of the negative tab.

[0019] In one aspect of the nonaqueous electrolyte secondary battery disclosed herein, the first region can have a region that is not opposed to the positive active material layer, and the width of the region in the negative electrode that is opposed to the positive electrode in the first region can be larger than the width of the region in the first region that is not opposed to the positive electrode. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 FIG. 1 is a perspective view schematically showing a nonaqueous electrolyte secondary battery according to an embodiment.

[0021] Figure 2 FIG. 2 is a schematic longitudinal sectional view along the II-II line of FIG. 1. Figure 1

[0022] Figure 3 Figure 1 ​​a schematic longitudinal sectional view of the III-III line of the electrode body.

[0023] Figure 4 is a schematic longitudinal sectional view of the III-III line of the electrode body. Figure 1 a schematic transverse sectional view of the IV-IV line of the electrode body.

[0024] Figure 5 is a perspective view schematically showing the electrode body group mounted to the sealing plate.

[0025] Figure 6 is a perspective view schematically showing the electrode body in which the positive second current collecting portion and the negative second current collecting portion are mounted.

[0026] Figure 7 is a schematic view showing the structure of the electrode body.

[0027] Figure 8 is a sectional view showing the configuration of the vicinity of the end edge having the negative tab of the negative electrode in the electrode body of one embodiment.

[0028] Figure 9 is a sectional view showing the configuration of the vicinity of the negative tab of the negative electrode in the electrode body of one embodiment.

[0029] Figure 10 is a sectional view showing the configuration of the vicinity of the end edge having the negative tab of the negative electrode in the electrode body of another embodiment.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] 10, battery case; 12, exterior body; 14, sealing plate; 20, electrode body group; 20a, 20b, 20c, electrode body; 22, positive electrode; 22a, positive electrode active material layer; 22c, positive electrode core; 22t, positive electrode tab; 24, negative electrode; 24a, negative electrode active material layer; 24c, negative electrode core; 24t, negative electrode tab; 24r, first region; 24s, inclined portion; 26, spacer; 30, positive electrode terminal; 40, negative electrode terminal; 50, positive electrode current collecting portion; 60, negative electrode current collecting portion; 100, nonaqueous electrolyte secondary battery; 120a, electrode body. DETAILED DESCRIPTION

[0032] Hereinafter, several preferred embodiments of the technology disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification, which are required for implementation of the technology (e.g., a general structure and a manufacturing process of a battery to which the technology is not imparted with features) can be understood as design matters of a person skilled in the art based on the existing technology in the art. The technology can be implemented based on the content disclosed in this specification and common technical knowledge in the art.

[0033] Note that in the present specification, the "nonaqueous electrolyte secondary battery" is a term for all power storage devices that use a nonaqueous electrolyte as a charge carrier and are capable of repeated charge and discharge accompanying movement of the charge carrier between the positive and negative electrodes, and is a concept that includes so-called secondary batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-hydrogen batteries, and capacitors (physical batteries) such as electric double-layer capacitors.

[0034] Figure 1 is a perspective view of the nonaqueous electrolyte secondary battery 100. Figure 2 is a schematic longitudinal sectional view along the II-II line of Figure 1 . Figure 3 is a schematic longitudinal sectional view along the III-III line of Figure 1 . Figure 4 is a schematic transverse sectional view along the IV-IV line of Figure 1 . Note that in the following description, the left, right, front, rear, upper, and lower in the drawings are denoted by the reference signs L, R, F, Rr, U, and D, respectively, and the short side direction, the long side direction orthogonal to the short side direction, and the up-down direction of the nonaqueous electrolyte secondary battery 100 are denoted by the reference signs X, Y, and Z, respectively. The long side direction Y is an example of the first direction disclosed herein, and the short side direction is an example of the second direction disclosed herein. However, these are merely directions for convenience of explanation, and the nonaqueous electrolyte secondary battery 100 is not limited in any way by the arrangement thereof.

[0035] As shown in Figure 2 , the nonaqueous electrolyte secondary battery 100 includes a battery case 10, an electrode body group 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, and a negative electrode current collector 60. Although not shown, the nonaqueous electrolyte secondary battery 100 also includes a nonaqueous electrolyte solution. The nonaqueous electrolyte secondary battery 100 is a lithium-ion secondary battery.

[0036] The battery case 10 is a frame that houses the electrode body group 20. Here, the battery case 10 has a flat and bottomed rectangular parallelepiped shape (square) outer shape. The material of the battery case 10 is not particularly limited as long as it is the same as that used in the past. The battery case 10 is preferably made of metal, and more preferably composed of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like. As shown in Figure 2 , the battery case 10 includes an outer body 12 having an opening 12h and a seal plate (cover) 14 that plugs the opening 12h.

[0037] As shown in Figure 1As shown, the outer casing 12 includes a bottom wall 12a, a pair of long sidewalls 12b extending from the bottom wall 12a and opposing each other, and a pair of short sidewalls 12c extending from the bottom wall 12a and opposing each other. The bottom wall 12a is generally rectangular. The bottom wall 12a is opposite to the opening 12h. The area of ​​the short sidewalls 12c is smaller than the area of ​​the long sidewalls 12b. The long sidewalls 12b and short sidewalls 12c are examples of the first and second sidewalls disclosed herein. A sealing plate 14 is installed on the outer casing 12 to block the opening 12h of the outer casing 12. The sealing plate 14 is opposite to the bottom wall 12a of the outer casing 12. The sealing plate 14 is generally rectangular in plan view. The battery housing 10 is integrated by joining (e.g., welding) the sealing plate 14 to the periphery of the opening 12h of the outer casing 12. The battery housing 10 is hermetically sealed (sealed).

[0038] like Figure 2 As shown, the sealing plate 14 is provided with an injection hole 15, a gas vent valve 17, and two terminal outlet holes 18 and 19. The injection hole 15 is used to inject electrolyte after the sealing plate 14 is assembled to the outer casing 12. The injection hole 15 is sealed by the sealing member 16. The gas vent valve 17 is configured to break when the pressure inside the battery casing 10 reaches a predetermined value, thereby venting the gas inside the battery casing 10 to the outside. The terminal outlet holes 18 and 19 are respectively formed at both ends in the long side direction Y of the sealing plate 14. The terminal outlet holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. The terminal outlet holes 18 and 19 each have an inner diameter that allows the positive terminal 30 and negative terminal 40 to pass through before installation on the sealing plate 14 (before riveting).

[0039] The positive terminal 30 and the negative terminal 40 are respectively fixed to the sealing plate 14. The positive terminal 30 is located on one side of the sealing plate 14 in the long side direction Y. Figure 1 , Figure 2 The negative terminal 40 is positioned on the other side of the sealing plate 14 in the Y direction along its long side. Figure 1 , Figure 2 (The right side). For example Figure 1 As shown, the positive terminal 30 and the negative terminal 40 are exposed on the outer surface of the sealing plate 14. Figure 2 As shown, the positive terminal 30 and the negative terminal 40 extend from the inside of the sealing plate 14 outward through the terminal lead-out holes 18 and 19. Here, the positive terminal 30 and the negative terminal 40 are riveted to the periphery of the sealing plate 14 surrounding the terminal lead-out holes 18 and 19 by riveting. Riveting portions are formed at the ends of the positive terminal 30 and the negative terminal 40 on the outer casing 12 side.

[0040] like Figure 2As shown, the positive terminal 30 is electrically connected to the positive electrode of the electrode group 20 via the positive current collecting portion 50 inside the exterior body 12. The negative terminal 40 is electrically connected to the negative electrode of the electrode group 20 via the negative current collecting portion 60 inside the exterior body 12. The positive terminal 30 and the negative terminal 40 are examples of the terminals disclosed herein.

[0041] The positive terminal 30 is preferably made of metal, and more preferably composed of, for example, aluminum or an aluminum alloy. The negative terminal 40 is preferably made of metal, and more preferably composed of, for example, copper or a copper alloy. The negative terminal 40 can also be composed of two conductive members joined and integrated. For example, the portion connected to the negative current collecting portion 60 can be composed of copper or a copper alloy, and the portion exposed on the surface outside the sealing plate 14 can be composed of aluminum or an aluminum alloy.

[0042] As shown, the positive terminal 30 is electrically connected to the positive electrode of the electrode group 20 via the positive current collecting portion 50 inside the exterior body 12. The negative terminal 40 is electrically connected to the negative electrode of the electrode group 20 via the negative current collecting portion 60 inside the exterior body 12. The positive terminal 30 and the negative terminal 40 are examples of the terminals disclosed herein. Figure 1 As shown, the positive terminal 30 is electrically connected to the positive electrode of the electrode group 20 via the positive current collecting portion 50 inside the exterior body 12. The negative terminal 40 is electrically connected to the negative electrode of the electrode group 20 via the negative current collecting portion 60 inside the exterior body 12. The positive terminal 30 and the negative terminal 40 are examples of the terminals disclosed herein.

[0043] Figure 5 is a perspective view schematically showing the electrode group 20 mounted to the sealing plate 14. Figure 6 is a perspective view schematically showing the electrode body 20a. In the nonaqueous electrolyte secondary battery 100 of the present embodiment, the electrode group 20 having a plurality of electrode bodies 20a, 20b, 20c is housed inside the battery case 10. However, the number of electrode bodies arranged inside one exterior body 12 is not particularly limited, and can be two or more (plural), or one. The detailed configuration will be described later, and the electrode bodies 20a, 20b, 20c each have a positive tab group 23 composed of a plurality of positive tabs 22t and a negative tab group 25 composed of a plurality of negative tabs 24t. The positive current collecting portion 50 constitutes a conduction path electrically connecting the positive tab group 23 and the positive terminal 30. In addition, the negative current collecting portion 60 constitutes a conduction path electrically connecting the negative tab group 25 and the negative terminal 40. Here, the electrode body 20a has the positive tab group 23 at one end portion, and the negative tab group 25 at the other end portion.

[0044] As shown, the positive terminal 30 is electrically connected to the positive electrode of the electrode group 20 via the positive current collecting portion 50 inside the exterior body 12. The negative terminal 40 is electrically connected to the negative electrode of the electrode group 20 via the negative current collecting portion 60 inside the exterior body 12. The positive terminal 30 and the negative terminal 40 are examples of the terminals disclosed herein. Figure 2 ,5 As shown in FIGS. 6, the positive electrode current collecting portion 50 includes a positive electrode first current collecting portion 51 and a positive electrode second current collecting portion 52. The positive electrode first current collecting portion 51 is a plate-shaped conductive member extending along the inner side surface of the sealing plate 14. The positive electrode second current collecting portion 52 is a plate-shaped conductive member extending in the up-down direction Z. The lower end portion of the positive electrode terminal 30 extends to the inside of the battery case 10 through the terminal lead-out hole 18 of the sealing plate 14, and is connected to the positive electrode first current collecting portion 51. On the other hand, as shown in FIGS. 6, the positive electrode second current collecting portion 52 is connected at one end to the positive electrode first current collecting portion 51, and is connected at the other end to the positive electrode tab group 23 of the electrode body group 20, forming a connection portion J. Here, the positive electrode tab group 23 of the electrode body group 20 is bent so that the positive electrode second current collecting portion 52 opposes the side of the electrode bodies 20a, 20b, 20c having the positive electrode tab group 23. As a result, the width of the positive electrode tab group 23 in the long direction Y can be reduced. As a result, the coating width of the positive electrode active material layer 22a and the negative electrode active material layer 24a of the electrode body group 20, which will be described later, in the long direction Y can be increased, and thus the capacity of the nonaqueous electrolyte secondary battery 100 can be increased. Note that the positive electrode first current collecting portion 51 and the positive electrode second current collecting portion 52 are preferably made of metal, and can be made of, for example, aluminum, an aluminum alloy, nickel, stainless steel, or the like. Figure 2 、 4 As shown in FIGS. 6, the positive electrode second current collecting portion 52 is connected at one end to the positive electrode first current collecting portion 51, and is connected at the other end to the positive electrode tab group 23 of the electrode body group 20, forming a connection portion J. Here, the positive electrode tab group 23 of the electrode body group 20 is bent so that the positive electrode second current collecting portion 52 opposes the side of the electrode bodies 20a, 20b, 20c having the positive electrode tab group 23. As a result, the width of the positive electrode tab group 23 in the long direction Y can be reduced. As a result, the coating width of the positive electrode active material layer 22a and the negative electrode active material layer 24a of the electrode body group 20, which will be described later, in the long direction Y can be increased, and thus the capacity of the nonaqueous electrolyte secondary battery 100 can be increased. Note that the positive electrode first current collecting portion 51 and the positive electrode second current collecting portion 52 are preferably made of metal, and can be made of, for example, aluminum, an aluminum alloy, nickel, stainless steel, or the like.

[0045] As shown in FIGS. 6, the positive electrode second current collecting portion 52 is connected at one end to the positive electrode first current collecting portion 51, and is connected at the other end to the positive electrode tab group 23 of the electrode body group 20, forming a connection portion J. Here, the positive electrode tab group 23 of the electrode body group 20 is bent so that the positive electrode second current collecting portion 52 opposes the side of the electrode bodies 20a, 20b, 20c having the positive electrode tab group 23. As a result, the width of the positive electrode tab group 23 in the long direction Y can be reduced. As a result, the coating width of the positive electrode active material layer 22a and the negative electrode active material layer 24a of the electrode body group 20, which will be described later, in the long direction Y can be increased, and thus the capacity of the nonaqueous electrolyte secondary battery 100 can be increased. Note that the positive electrode first current collecting portion 51 and the positive electrode second current collecting portion 52 are preferably made of metal, and can be made of, for example, aluminum, an aluminum alloy, nickel, stainless steel, or the like. Figure 2 、 5 As shown in FIGS. 6, the positive electrode second current collecting portion 52 is connected at one end to the positive electrode first current collecting portion 51, and is connected at the other end to the positive electrode tab group 23 of the electrode body group 20, forming a connection portion J. Here, the positive electrode tab group 23 of the electrode body group 20 is bent so that the positive electrode second current collecting portion 52 opposes the side of the electrode bodies 20a, 20b, 20c having the positive electrode tab group 23. As a result, the width of the positive electrode tab group 23 in the long direction Y can be reduced. As a result, the coating width of the positive electrode active material layer 22a and the negative electrode active material layer 24a of the electrode body group 20, which will be described later, in the long direction Y can be increased, and thus the capacity of the nonaqueous electrolyte secondary battery 100 can be increased. Note that the positive electrode first current collecting portion 51 and the positive electrode second current collecting portion 52 are preferably made of metal, and can be made of, for example, aluminum, an aluminum alloy, nickel, stainless steel, or the like. Figure 2 、 4 As shown in FIGS. 6, the positive electrode second current collecting portion 52 is connected at one end to the positive electrode first current collecting portion 51, and is connected at the other end to the positive electrode tab group 23 of the electrode body group 20, forming a connection portion J. Here, the positive electrode tab group 23 of the electrode body group 20 is bent so that the positive electrode second current collecting portion 52 opposes the side of the electrode bodies 20a, 20b, 20c having the positive electrode tab group 23. As a result, the width of the positive electrode tab group 23 in the long direction Y can be reduced. As a result, the coating width of the positive electrode active material layer 22a and the negative electrode active material layer 24a of the electrode body group 20, which will be described later, in the long direction Y can be increased, and thus the capacity of the nonaqueous electrolyte secondary battery 100 can be increased. Note that the positive electrode first current collecting portion 51 and the positive electrode second current collecting portion 52 are preferably made of metal, and can be made of, for example, aluminum, an aluminum alloy, nickel, stainless steel, or the like.

[0046] In the nonaqueous electrolyte secondary battery 100 of the present embodiment, various insulating members that prevent conduction between the battery case 10 and the electrode body group 20 are installed. Specifically, an external insulating member 92 is interposed between the positive electrode external conductive member 32 (or the negative electrode external conductive member 42) and the outer side surface of the sealing plate 14 (see FIG. 2). Thus, conduction between the positive electrode external conductive member 32, the negative electrode external conductive member 42, and the sealing plate 14 can be prevented. In addition, a gasket 90 is installed in each of the terminal lead-out holes 18, 19 of the sealing plate 14 (see FIG. 2). Thus, conduction between the positive electrode terminal 30 (or the negative electrode terminal 40) that penetrates the terminal lead-out holes 18, 19 and the sealing plate 14 can be prevented. In addition, an internal insulating member 94 is disposed between the positive electrode first current collecting portion 51 (or the negative electrode first current collecting portion 61) and the inner side surface of the sealing plate 14. The internal insulating member 94 has a plate-shaped base portion 94a interposed between the positive electrode first current collecting portion 51 (or the negative electrode first current collecting portion 61) and the inner side surface of the sealing plate 14. Thus, conduction between the positive electrode first current collecting portion 51, the negative electrode first current collecting portion 61, and the sealing plate 14 can be prevented. Further, the internal insulating member 94 has a protruding portion 94b that protrudes from the inner side surface of the sealing plate 14 toward the electrode body group 20 (see FIG. 2 and FIG. 3). Thus, movement of the electrode body group 20 in the up-down direction Z can be restricted, and direct contact between the electrode body group 20 and the sealing plate 14 can be prevented. Furthermore, the electrode body group 20 is housed inside the battery case 10 in a state covered by an electrode body holder 29 composed of an insulating resin sheet (see FIG. 2). Thus, direct contact between the electrode body group 20 and the outer case 12 can be prevented. Note that the material of each of the above-described insulating members is not particularly limited as long as it has a predetermined insulating property. As an example, a synthetic resin material such as a polyolefin-based resin (e.g., polypropylene (PP), polyethylene (PE)), a fluorine-based resin (e.g., perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE)), or the like can be used. Figure 1 ). Thus, conduction between the positive electrode external conductive member 32, the negative electrode external conductive member 42, and the sealing plate 14 can be prevented. In addition, a gasket 90 is installed in each of the terminal lead-out holes 18, 19 of the sealing plate 14 (see Figure 2 ). Thus, conduction between the positive electrode external conductive member 32, the negative electrode external conductive member 42, and the sealing plate 14 can be prevented. In addition, a gasket 90 is installed in each of the terminal lead-out holes 18, 19 of the sealing plate 14 (see Figure 2 and Figure 3 ). Thus, conduction between the positive electrode external conductive member 32, the negative electrode external conductive member 42, and the sealing plate 14 can be prevented. In addition, a gasket 90 is installed in each of the terminal lead-out holes 18, 19 of the sealing plate 14 (see Figure 3 ). Thus, conduction between the positive electrode external conductive member 32, the negative electrode external conductive member 42, and the sealing plate 14 can be prevented. In addition, a gasket 90 is installed in each of the terminal lead-out holes 18, 19 of the sealing plate 14 (see

[0047] The nonaqueous electrolyte solution can be the same as in the past and is not particularly limited. The nonaqueous electrolyte solution contains, for example, a nonaqueous solvent and a supporting salt. The nonaqueous solvent contains, for example, a carbonate such as ethylene carbonate, dimethyl carbonate, or methyl ethyl carbonate. The supporting salt is, for example, a lithium salt containing fluorine such as LiPF6. However, the nonaqueous electrolyte solution can be in a solid state (solid electrolyte) and integrated with the electrode body group 20.

[0048] Figure 7 is a schematic view showing the structure of the electrode body 20a. In addition, Figure 8This is a cross-sectional view showing the structure near the end edge 24e of the negative electrode 24 with the negative electrode tab 24t in an electrode body 20a according to one embodiment. It should be noted that the following detailed description uses electrode body 20a as an example, but the same structure can also be used for electrode bodies 20b and 20c. Figure 7 As shown, the electrode body 20a has a positive electrode 22 and a negative electrode 24. Here, the electrode body 20a is a flat, wound electrode body formed by stacking strip-shaped positive electrodes 22 and strip-shaped negative electrodes 24 with strip-shaped spacers 26 and winding them around a winding shaft WL. The positive electrode 22 and the negative electrode 24 are examples of the first electrode and the second electrode disclosed herein.

[0049] Electrode body 20a is disposed inside the outer casing 12 with its winding axis WL parallel to the long side direction Y. In other words, electrode body 20a is disposed inside the outer casing 12 with its winding axis WL parallel to the bottom wall 12a and orthogonal to the short side wall 12c. The end face of electrode body 20a (in other words, the laminated surface where the positive electrode 22, negative electrode 24, and spacer 26 are stacked) Figure 7 The end face on the long side direction Y) is opposite to the short sidewall 12c.

[0050] like Figure 3 As shown, the electrode body 20a has a pair of curved portions 20r opposite to the bottom wall 12a and the sealing plate 14 of the outer body 12, and a flat portion 20f connecting the pair of curved portions 20r and opposite to the long side wall 12b of the outer body 12. However, the electrode body 20a may also be a stacked electrode body formed by stacking multiple square (typically rectangular) positive electrodes and multiple square (typically rectangular) negative electrodes in an insulated state.

[0051] The spacer 26 is a component used to insulate the positive electrode active material layer 22a of the positive electrode 22 from the negative electrode active material layer 24a of the negative electrode 24. As the spacer 26, a porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is preferred. Alternatively, the spacer 26 may have a heat resistance layer (HRL) containing inorganic fillers on the surface of the resin sheet. Examples of inorganic fillers include alumina, boehmite, aluminum hydroxide, and titanium dioxide. Furthermore, an adhesive layer is preferably provided on one or both surfaces of the spacer 26. The adhesive layer improves adhesion to the contacting positive or negative electrode active material layer. The adhesive layer may contain, for example, polyvinylidene fluoride (PVdF) as an adhesive component. Alternatively, the adhesive layer may contain inorganic particles such as alumina or boehmite. The adhesive layer can be provided on the surface of the resin sheet or on the surface of the HRL.

[0052] like Figure 7As shown, the positive electrode 22 has a positive electrode core 22c and a positive electrode active material layer 22a and a positive electrode protective layer 22p formed on at least one surface (here, both surfaces) of the positive electrode core 22c. However, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments. The positive electrode core 22c is strip-shaped. The positive electrode core 22c is made of conductive metals such as aluminum, aluminum alloy, nickel, and stainless steel. The positive electrode core 22c is a metal foil, specifically an aluminum foil.

[0053] One end edge (in the width direction of the positive electrode core 22c, the long side direction Y in the figure, i.e., the direction orthogonal to the long side direction on the surface of the positive electrode core 22c) Figure 7 Multiple positive electrode tabs 22t are provided at the left end. The multiple positive electrode tabs 22t are respectively oriented towards one side in the width direction ( Figure 7 The positive electrode tabs 22t protrude from the spacer 26 in the long side direction Y. The positive electrode tabs 22t are spaced apart (intermittently) along the long side direction of the positive electrode 22. Each of the positive electrode tabs 22t is trapezoidal. The positive electrode tabs 22t are part of the positive electrode core 22c and are made of metal foil (in this case, aluminum foil). The positive electrode tabs 22t have portions of the positive electrode core 22c where the positive electrode active material layer 22a and the positive electrode protective layer 22p are not formed (core exposed portion). However, the positive electrode tabs 22t can also be components different from the positive electrode core 22c. Furthermore, the positive electrode tabs 22t can be located at the other end in the width direction (…). Figure 7 (The right end), or can be set at both ends in the width direction.

[0054] like Figure 4 As shown, one end of the plurality of positive electrode tabs 22t in the width direction (long side direction Y) Figure 4 The left end) is stacked to form multiple positive electrode tabs 22t of the positive electrode tab group 23. The dimensions of these tabs (length in the long side direction Y and width orthogonal to the long side direction Y) are as follows: Figure 7 The connection state with the positive current collector 50 can be considered, and appropriate adjustments can be made according to its formation position, for example. The plurality of positive electrode tabs 22t are of different sizes, with their outer ends aligned when bent. The positive electrode tab group 23 is an example of the electrode tab group disclosed herein.

[0055] like Figure 7As shown, the positive electrode active material layer 22a is provided in a strip shape along the long side direction of the strip-shaped positive electrode core 22c. The positive electrode active material layer 22a contains a positive electrode active material capable of reversibly occluding and releasing charge carriers. As the positive electrode active material, it is preferably at least one of Ni, Co, and Mn, and for example, a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide can be used. When the total solid content of the positive electrode active material layer 22a is set to 100% by mass, the positive electrode active material accounts for approximately 80% by mass or more, typically 90% by mass or more, and for example, it can also account for 95% by mass or more. The positive electrode active material layer 22a may also contain any components other than the positive electrode active material, such as a conductive material, an adhesive, and various additive components. As the conductive material, for example, a carbon material such as carbon black (e.g., acetylene black (AB)) can be used. As the adhesive, for example, PVdF can be used.

[0056] As Figure 7 shown, the positive electrode protective layer 22p is provided at the boundary between the positive electrode core 22c and the positive electrode active material layer 22a in the width direction (long side direction Y). The positive electrode protective layer 22p is provided at one end portion ( Figure 7 the left end portion) of the positive electrode core 22c in the width direction (long side direction Y). The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a.The positive electrode protective layer 22p contains an inorganic filler (e.g., alumina). When the total solid content of the positive electrode protective layer 22p is set to 100% by mass, the inorganic filler accounts for approximately 50% by mass or more, typically 70% by mass or more, and for example, it can also account for 80% by mass or more. The positive electrode protective layer 22p may also contain any components other than the inorganic filler, such as a conductive material, an adhesive, and various additive components. The conductive material and the adhesive may be the same as the conductive material and the adhesive exemplified as those that can be contained in the positive electrode active material layer 22a.

[0057] The positive electrode 22 is configured such that in the width direction (long side direction Y), the thickness of the positive electrode active material layer 22a at the central portion of the positive electrode 22 is set to T1, and the thickness of the positive electrode active material layer 22a at the end portion 22e ( Figure 7 , 8 the right end portion) opposite to the first region 24r of the negative electrode active material layer 24a described later is set to T2, the thickness ratio (T2 / T1) is 0.95 < T2 / T1 < 1.05, and it is preferably configured such that 0.97 < T2 / T1 < 1.03. In other words, the thickness of the positive electrode active material layer 22a is configured such that from the central portion to the end portion opposite to the first region 24r of the negative electrode active material layer 24a described later, the thickness does not substantially change. It should be noted that in Figure 8 , the thickness of the positive electrode active material layer 22a at the central portion of the positive electrode 22 is Figure 8The left end portion of the positive electrode active material layer 22a in the positive electrode 22 is formed in such a manner that the thicknesses of the left end portion and the right end portion of the positive electrode active material layer 22a are the same (i.e., the thickness T1).

[0058] Note that, in the present specification, as shown in FIG. 1, the central portion of the positive electrode 22 refers to a square region of 2 cm on a side centered on the intersection of a straight line CL1 extending in the long direction Y along the center of the width of the electrode body 20a in the width direction (long direction Y) and a straight line CL2 extending in the long direction Y along the center of the width of the tab 22t in the direction in which the tab 22t protrudes (long direction Y). Thus, the thickness T1 of the positive electrode active material layer 22a in the central portion of the positive electrode 22 refers to the average thickness of the positive electrode active material layer 22a in this region. In addition, the thickness T2 of the positive electrode active material layer 22a refers to the average thickness in the range of a rectangle having a length in the width direction (long direction Y) opposite the first region 24r of the negative electrode active material layer 24a as the short side and a length of 2 cm in the long direction Y as the long side with the straight line CL2 described above as the center. Figure 7

[0059] From the viewpoint of high capacity, the weight per unit area of the positive electrode active material layer 22a (the mass of the positive electrode active material layer 22a per unit area) may, for example, be 300 g / m 2 or more, and preferably 400 g / m 2 or more. In addition, from the viewpoint of reducing the thickness of the electrode body 20a, the weight per unit area may, for example, be 700 g / m 2 or more, and preferably 600 g / m 2 or more. In addition, the weight per unit area m1 of the positive electrode active material layer 22a in the central portion of the positive electrode 22 is preferably the same degree as the weight per unit area m2 of the positive electrode active material layer 22a in the end portion 22e of the positive electrode 22, and may, for example, be 0.95 < m2 / m1 < 1.05, and preferably 0.97 < m2 / m1 < 1.03. Note that the measurement region of the weight per unit area m1 is the same region as the thickness T1 described above, and the measurement region of the weight per unit area m2 is the same region as the thickness T2 described above.

[0060] The length of the positive electrode active material layer 22a in the width direction (winding axis WL direction) is not particularly limited and may, for example, be 20 cm or more, or 25 cm or more. Thus, it is possible to make the nonaqueous electrolyte secondary battery 100 high capacity. In addition, from the viewpoint of eliminating reaction unevenness of the electrode body 20a, the length of the positive electrode active material layer 22a in the width direction may, for example, be 50 cm or less, or 40 cm or less.

[0061] ​The surface roughness (Ra) of the surface of the positive electrode active material layer 22a that contacts the spacer 26 can be, for example, 0.2 μm to 0.6 μm. It should be noted that, in this specification, "surface roughness" refers to the arithmetic mean roughness based on JIS B 0601:2001.

[0062] like Figure 7 As shown, the negative electrode 24 has a negative electrode core 24c and a negative electrode active material layer 24a formed on at least one surface (in this case, both surfaces) of the negative electrode core 24c. The negative electrode core 24c is strip-shaped. The negative electrode core 24c is made of conductive metals such as copper, copper alloy, nickel, and stainless steel. The negative electrode core 24c is a metal foil, specifically a copper foil.

[0063] One end edge 24e (in the width direction (long side direction Y) of the negative electrode core 24c) Figure 7 Multiple negative electrode tabs 24t are provided at the right end. These multiple negative electrode tabs 24t face one side along the long side direction Y. Figure 7 The right side of the negative electrode 24 protrudes. Multiple negative electrode tabs 24t protrude beyond the spacer 26 in the long side direction Y. The multiple negative electrode tabs 24t are spaced apart (intermittently) along the long side direction of the negative electrode 24. Each of the multiple negative electrode tabs 24t is trapezoidal. The negative electrode tabs 24t are part of the negative electrode core 24c and are made of metal foil (in this case, copper foil). Here, the negative electrode tabs 24t have a portion of the negative electrode core 24c where the negative electrode active material layer 24a is not formed (core exposed portion). However, the negative electrode tabs 24t can also be components different from the negative electrode core 24c. Furthermore, the negative electrode tabs 24t can be located at the other end in the long side direction Y ( Figure 7 The left end can be located at one end of the long side (Y), or at the two ends of the long side (Y).

[0064] like Figure 4 As shown, one end edge 24e of the multiple negative electrode tabs 24t in the width direction (long side direction Y) is ( Figure 6 The right end of each negative electrode tab is stacked to form a negative electrode tab assembly 25. The dimensions of the multiple negative electrode tabs 24t (length of the long side in the Y direction and width orthogonal to the long side in the Y direction, refer to...) Figure 7 The connection state with the negative electrode current collector 60 can be considered, and appropriate adjustments can be made according to its formation position, for example. The multiple negative electrode tabs 24t are of different sizes, with their outer ends aligned when bent. The negative electrode tab assembly 25 is an example of the electrode tab assembly disclosed herein.

[0065] The negative electrode active material layer 24a is provided in a band shape along the long side direction of the negative electrode core 24c. The negative electrode active material layer 24a contains a negative electrode active material (for example, a carbon material such as graphite, a silicon-based material such as Si, SiO, or the like) that can reversibly occlude and release a charge carrier. When the solid content of the negative electrode active material layer 24a is taken as 100% by mass, the negative electrode active material accounts for substantially 80% by mass or greater, typically 90% by mass or greater, and for example, can account for 95% by mass or greater. The negative electrode active material layer 24a can contain any component other than the negative electrode active material, such as a binder, a dispersant, various additive components, and the like. As the binder, for example, a rubber-based material such as styrene butadiene rubber (SBR) or the like can be used. As the dispersant, for example, a cellulose-based material such as carboxymethyl cellulose (CMC) or the like can be used.

[0066] The length of the negative electrode active material layer 24a in the width direction (winding axis WL direction) is not particularly limited and can be, for example, 20 cm or greater, 25 cm or greater. Thereby, the nonaqueous electrolyte secondary battery 100 can be made high in capacity. In addition, from the viewpoint of eliminating reaction unevenness of the electrode body 20a, the length of the negative electrode active material layer 24a in the width direction can be, for example, 50 cm or less, 40 cm or less.

[0067] Figure 8 is a cross-sectional view that shows the configuration of the vicinity of the end edge 24e of the negative electrode 24 of the electrode body 20a in one embodiment. The negative electrode active material layer 24a has a first region 24r in the width direction (long side direction Y) of the negative electrode 24 between the end edge 24e and a position 5 mm from the end edge 24e (in the drawing, the range of W1). The end portion 22e of the positive electrode 22 in the width direction (long side direction Y) is disposed so as to face at least a part of the first region 24r with the spacer 26 interposed therebetween. In this embodiment, the end portion 22e of the positive electrode 22 is disposed so as to face a part of the first region in the width direction, and the first region 24r has a region 24r1 that faces the end portion 22e of the positive electrode 22 and a region 24r2 that does not face the end portion 22e of the positive electrode 22. Note that the end edge 24e of the negative electrode 24 is disposed inward of the end edge of the end portion 26e of the spacer 26.

[0068] The negative active material layer 24a in the first region 24r is configured to have a lower density than the negative active material layer 24a of the central portion of the negative electrode 24. Specifically, when the weight per unit area (the mass of the negative active material layer 24a per unit area) of the negative active material layer 24a of the central portion of the negative electrode 24 is set to Ml, and the weight per unit area (the mass of the negative active material layer 24a per unit area) of the negative active material layer 24a of the region 24rl of the first region 24r opposite to the end portion 22e of the positive electrode 22 is set to M2, the negative electrode 24 is configured to satisfy the condition 0.95 < M2 / Ml < 1. Further, it is preferable that the negative electrode 24 be configured to satisfy the condition 0.95 < M2 / Ml < 0.99. By configuring the negative active material layer 24a in the first region 24r to have a relatively low density (i.e., M2 / Ml < 1, preferably M2 / Ml < 0.99), the non-aqueous electrolyte solution easily penetrates into the negative active material layer 24a, and thus the liquid injection property can be improved. On the other hand, in the case where the value of M2 / Ml is too small, the amount of the negative active material contained in the negative active material layer 24a in the region 24rl opposite to the end portion of the positive electrode 22 becomes small. Thus, not all of the lithium ions supplied from the opposite positive active material layer 22a can be occluded, and thus it is likely that lithium deposition easily occurs. Therefore, by setting 0.95 < M2 / Ml, the occlusion ability of the lithium ions can be ensured, and thus lithium deposition can be suppressed.

[0069] Note that, in the present specification, the central portion of the negative electrode 24 refers to a region of a square shape of 2 cm on a side, centered on the intersection of a straight line CLl extending in the width direction (longitudinal direction Y) of the electrode body 20a along the longitudinal direction and a straight line CL3 extending in the longitudinal direction of the negative tab 24t along the protruding direction (longitudinal direction Y) of the positive tab 22t, as shown in FIG. 6. Figure 7

[0070] Further, the weight per unit area M2 refers to the weight per unit area of the negative active material layer 24a of the region 24rl of the first region 24r opposite to the end portion 22e of the positive electrode 22 in a range of 2 cm in the longitudinal direction of the negative electrode core 24c centered on the straight line CL3. With respect to the weight per unit area, for example, a test piece obtained by cutting the negative electrode 24 in the range is prepared, and the negative active material layer 24a formed on one side of the test piece is peeled from the negative electrode core 24c, and the mass of the peeled negative active material layer can be measured.

[0071] From the viewpoint of high capacity, the weight per unit area of the negative active material layer 24a may, for example, be 200 g / m 2 or more, and preferably 220 g / m 2 or more. Further, from the viewpoint of reducing the thickness of the electrode body 20a, the weight per unit area may, for example, be 400 g / m​2 The preferred value is 350g / m³. 2 It should be noted that the above-mentioned weight per unit area refers to the total weight per unit area of ​​the negative electrode active material layer 24a.

[0072] In the width direction (long side direction Y) of the negative electrode 24, the width (length) W2 of the region 24r1 in the first region 24r that is opposite to the end 22e of the positive electrode 22 is preferably greater than the width (length) W3 of the region 24r2 that is not opposite to the end 22e of the positive electrode 22 (i.e., W2 > W3). For example, when the width W1 of the first region 24r is set to 100%, the width W2 of the region 24r1 that is opposite to the end 22e of the positive electrode 22 is preferably 51% or more, more preferably 55% or more. As a result, the region of the negative electrode 24 opposite to the positive electrode 22 is widened, thus enabling a higher capacity non-aqueous electrolyte secondary battery. In addition, although not particularly limited, by having a region 24r2 in the first region 24r that is not opposite to the end 22e of the positive electrode 22, lithium ions that can diffuse from the end 22e of the positive electrode 22 during charging can be appropriately encapsulated. Therefore, in the width W1 of the first region 24r, the width W2 of the region 24r1 opposite to the end 22e of the positive electrode 22 is preferably 95% or less (that is, the width W3 of the region 24r2 not opposite to the end of the positive electrode is 5% or more), and can be 90% or less (W3 is 10% or more) or 85% or less (W3 is 15% or more).

[0073] The width (length) W3 of the region 24r2 that is not opposite to the end of the positive electrode 22 is typically 0.25 mm or more, for example, it can be 0.5 mm or more or 1 mm or more. In addition, the width (length) W3 of the region 24r2 that is not opposite to the end of the positive electrode 22 is typically less than 3.5 mm, for example, it can be less than 3 mm.

[0074] like Figure 8 As shown, in this embodiment, a sloping portion 24s is provided in the first region 24r, where the thickness of the negative electrode active material layer 24a gradually decreases towards the end edge 24e. By providing the sloping portion 24s, a gap is created between the negative electrode active material layer 24a and the spacer 26. This allows non-aqueous electrolyte to enter through this gap, thus improving the liquid injection capability of the electrode body 20a. It should be noted that in this embodiment, the sloping portion 24s is provided throughout the first region 24r, but it is not limited to this; for example, at least a portion of the first region 24r may also have the sloping portion 24s.

[0075] In the thickness T3 of the negative electrode active material layer 24a in the central portion of the negative electrode 24 and the thickness T4 of the negative electrode active material layer 24a at the position opposed to the end edge of the positive electrode 22 in the first region 24r, T4 / T3 is preferably 0.9 or greater and less than 1.0, and more preferably 0.95 or greater and less than 1.0. Thereby, improvement in the liquid injection property and securing of the lithium ion occluding capacity of the negative electrode active material can be appropriately achieved. In addition, it is preferable that the thickness ratio (T2 / T1) of the positive electrode active material layer 22a described above and the thickness ratio (T4 / T3) of the negative electrode active material layer 24a described above be T2 / T1 > T4 / T3. Note that, in the Figure 8 , the thickness of the negative electrode active material layer 24a in the central portion of the negative electrode 24 is formed to be the same as the thickness of the left end portion of the negative electrode active material layer 24a in the Figure 8 . The thickness T3 refers to the average thickness of the negative electrode active material layer 24a in the central portion of the negative electrode 24. In addition, the thickness T4 refers to the average thickness of the negative electrode active material layer 24a in the first region 24r opposed to the end edge of the positive electrode 22 in a range of 2 cm in the long direction of the negative electrode core 24c with the straight line CL3 as the center.

[0076] Figure 9 is a cross-sectional view showing the configuration in the vicinity of the negative electrode tab 24t of the negative electrode 24 in the electrode body 20a of one embodiment. As shown in Figure 9 , in the present embodiment, the negative electrode active material layer 24a protrudes from the end portion 26e of the spacer 26 in the protruding direction of the negative electrode tab 24t (the right direction in Figure 9 ), and is also formed on the negative electrode tab 24t. Thereby, when the negative electrode core 24c is cut to form the negative electrode tab 24t, even if a burr is generated at the cut portion of the negative electrode core 24c, the negative electrode active material layer 24a is interposed between the burr and the spacer 26, and thus damage to the spacer 26 by the burr can be prevented.

[0077] From the viewpoint of improving the liquid injection property, the length W4 in the width direction of the inclined portion 24s of the negative electrode active material layer 24a is preferably, for example, 5 mm or greater, and more preferably 8 mm or greater. In addition, from the viewpoint of securing the relative capacitance ratio, the length W4 is preferably, for example, 20 mm or less, and more preferably 18 mm or less.

[0078] In addition, from the viewpoint of improving the liquid injection property, the length W5 in the width direction of the region of the inclined portion 24s of the negative electrode active material layer 24a opposed to the positive electrode active material layer 22a is preferably 3 mm or greater, and more preferably 4 mm or greater. In addition, from the viewpoint of high capacity, the length W5 is, for example, 10 mm or less, and preferably 8 mm or less.

[0079] The length W5 in the width direction of the region of the inclined portion 24s of the negative electrode active material layer 24a opposite to the positive electrode active material layer 22a and the length W6 in the width direction from the end edge of the negative electrode active material layer 24a on the negative electrode tab 24t to the position where the negative electrode active material layer 24a is opposite to the end edge of the positive electrode 22 have a length ratio (W5 / W6) of preferably 0.6 or more, more preferably 0.8 or more, and further preferably 1 or more. If this ratio is satisfied, the liquid injection property can be further improved. In order to cause the negative electrode active material layer 24a to protrude in the protruding direction of the negative electrode tab 24t from the end portion 26e of the spacer 26, for example, the length ratio (W5 / W6) can be 3 or less, for example, 2 or less.

[0080] From the viewpoint of preventing damage to the spacer 26 due to burrs that can occur when the negative electrode tab 24t is formed, the length W7 in the width direction from the end edge of the negative electrode active material layer 24a on the negative electrode tab 24t to the end edge 24e of the negative electrode 24 (i.e., the width (length) of the negative electrode active material layer 24a on the negative electrode tab 24t) is, for example, 1.2 mm or more, and preferably 2 mm or more. From the viewpoint of ensuring the area of the exposed portion of the negative electrode core 24c for joining the negative electrode tab 24t and the negative electrode second current collector portion 62, the length W7 is, for example, preferably 5 mm or less, and more preferably 4 mm or less.

[0081] The length ratio (W7 / W3) between the width (length) W7 of the negative electrode active material layer 24a on the negative electrode tab 24t in the width direction and the width (length) W3 of the region 24r2 in the first region 24r that is not opposite to the end portion 22e of the positive electrode 22 is preferably 1 or more, and more preferably 1.2 or more. The length ratio (W7 / W3) is, for example, 15 or less, and can be 10 or less, 5 or less, or 2 or less.

[0082] The surface roughness Ra of the surface of the negative electrode active material layer 24a that contacts the spacer 26 can be, for example, 0.4 μm to 0.8 μm. The surface roughness of the surface of the negative electrode active material layer 24a that contacts the spacer 26 is preferably greater than the surface roughness of the surface of the positive electrode active material layer 22a that contacts the spacer 26. As a result, a gap is easily formed between the negative electrode active material layer 24a and the spacer 26, and the liquid injection property is improved.

[0083] An example of a method for manufacturing the electrode body 20a will be described below. The method for manufacturing the electrode body 20a includes, for example, a negative electrode precursor preparation step, a negative electrode precursor cutting step, and an electrode body construction step. Note that the manufacturing method disclosed herein can further include other steps at any stage.

[0084] In the negative electrode precursor preparation step, the negative electrode active material layer 24a is formed by applying a paste for forming a negative electrode active material layer to both surfaces of the strip-shaped negative electrode core 24c and drying it. At this time, at the end portions in the width direction of the negative electrode core 24c, so-called sagging occurs in the applied paste, and thus the thickness of the end portions of the negative electrode active material layer formed gradually decreases toward the end edges. Therefore, in the portion where the sagging occurs, the weight per unit area of the negative electrode active material layer becomes relatively small. Thus, in the portion where the sagging occurs, the lithium ion occluding capacity of the negative electrode active material layer is relatively low, and thus if this portion is opposed to the positive electrode, lithium deposition is likely to occur.

[0085] Therefore, in the negative electrode precursor cutting step that follows, the end portion of the negative electrode precursor is cut so as to remove the portion where the sagging described above occurs. At this time, instead of cutting and removing the portion where the sagging occurs entirely, the cutting is performed so as to leave the sagging slightly, and thus a negative electrode 24 in which the weight per unit area Ml of the negative electrode active material layer 24a of the central portion of the negative electrode 24 and the weight per unit area M2 of the negative electrode active material layer 24a of the region 24rl in the first region 24r that is opposed to the end portion 22e of the positive electrode 22 satisfy the condition 0.95 < M2 / Ml < 1 can be realized. Note that the cut portion at this time is the end edge 24e of the negative electrode 24. In addition, in the negative electrode precursor cutting step, the end portion of the negative electrode precursor can also be processed so as to form a negative electrode tab 24t. The method of cutting the negative electrode precursor is not particularly limited, and for example, laser cutting can be appropriately employed.

[0086] In the electrode body construction process, the positive electrode 22 and the negative electrode 24 are stacked with the separator 26 interposed therebetween, and are pressed from the stacking direction, thereby constructing the electrode body 20a. The pressing method can be implemented in accordance with a publicly known method. The electrode body 20a described above is a wound electrode body, and is thus wound around a winding shaft as the center before being pressed. In the electrode body construction process, the adjustment is performed in such a manner that the end portion 22e of the positive electrode 22 is in a positional relationship with at least a part of the first region 24r of the negative electrode 24. From the viewpoint of suppressing deviation of the positional relationship, the separator 26 is appropriately used as a separator having an adhesive layer on both surfaces. Generally, if the separator 26 having an adhesive layer is used, it is difficult for a gap to be generated between the separator 26 and the positive electrode active material layer 22a and the negative electrode active material layer 24a, and there is a tendency that the liquid injection property deteriorates. However, the negative electrode 24 manufactured as described above has a relatively small weight per unit area of the end portion (portion where the collapse occurs) of the negative electrode active material layer 24a, and thus the adhesion of the adhesive layer to the negative electrode active material layer 24a can be weakened in the vicinity of the end portion. In particular, by leaving the collapse (inclined portion) at the end portion of the negative electrode active material layer 24a, even if the pressing is performed, the adhesive layer is difficult to adhere to the inclined portion, and the adhesion becomes weaker or is not adhered. Thus, even if the separator 26 having an adhesive layer is used, the non-aqueous electrolyte solution easily enters the negative electrode active material layer, and the liquid injection property can be improved.

[0087] The non-aqueous electrolyte secondary battery 100 can be used for various uses, and is preferably used as a driving power source for a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), an electric vehicle (BEV), or the like. The non-aqueous electrolyte secondary battery 100 can also be appropriately used as a battery pack in which a plurality of non-aqueous electrolyte secondary batteries 100 are arranged in a predetermined arrangement direction and a load is applied from the arrangement direction by a restraining mechanism.

[0088] Note that, as an example, the non-aqueous electrolyte secondary battery 100 having the square battery case 10 is described, but is not particularly limited thereto. For example, it can be a cylindrical non-aqueous electrolyte secondary battery in which a cylindrical battery case is used instead of the square battery case 10, a laminate-type non-aqueous electrolyte secondary battery in which a laminate film is used instead of the battery case 10, or the like.

[0089] The above describes an embodiment of the present technology, but the above-described embodiment is merely an example. The present technology can be implemented in various other forms. The technology recited in the claims includes technology obtained by various modifications and changes to the above-described example embodiment. For example, a part of the above-described embodiment can be replaced with another modification, or another modification can be added to the above-described embodiment. In addition, if the technical feature is not described as being essential, it can be appropriately deleted.

[0090] For example, in the above embodiment, the negative electrode active material layer 24a has an inclined portion 24s. However, it is not limited to this. For example, as Figure 10 As shown in the electrode body 120a, it is also possible to omit the inclined portion in the first region 24r of the negative electrode active material layer 24a. In this case, the unit area weight M1 of the negative electrode active material layer 24a in the central part of the negative electrode 24 and the unit area weight M2 of the negative electrode active material layer 24a in the region 24r1 opposite to the end 22e of the positive electrode 22 in the first region 24r satisfy the condition 0.95.

Claims

1. A nonaqueous electrolyte secondary battery comprising an electrode body including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode core and a positive electrode active material layer formed on both surfaces of the positive electrode core, the negative electrode includes a negative electrode core and a negative electrode active material layer formed on both surfaces of the negative electrode core, one end edge of the negative electrode in a width direction of the negative electrode is provided with a negative electrode tab composed of a portion of the negative electrode core and protruding from the end edge, the negative electrode active material layer has a first region between the end edge and a region 5 mm from the end edge in the width direction of the negative electrode, an end portion of the positive electrode opposes at least a portion of the first region via the separator, a thickness Tl of the positive electrode active material layer at a central portion of the positive electrode and a thickness T2 of the positive electrode active material layer at the end portion of the positive electrode satisfy a relationship of 0.95 < T2 / Tl < 1.05, a weight per unit area of the negative electrode active material layer at a central portion of the negative electrode, that is, a mass Ml of the negative electrode active material layer per unit area, and a weight per unit area of the negative electrode active material layer in a region of the first region that opposes the positive electrode active material layer, that is, a mass M2 of the negative electrode active material layer per unit area satisfy a condition of 0.95 < M2 / Ml < 1, and the negative electrode active material layer is also formed on the negative electrode tab in a direction in which the negative electrode active material layer protrudes from an end portion of the separator toward the negative electrode tab.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein in the first region, the negative electrode active material layer is formed in a manner in which a thickness of the negative electrode active material layer gradually decreases toward the end edge.

3. The nonaqueous electrolyte secondary battery according to claim 1, wherein the positive electrode has a positive electrode tab composed of a portion of the positive electrode core, and the electrode body has a plurality of the negative electrode tabs at one end portion and a plurality of the positive electrode tabs at the other end portion.

4. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the electrode body is a jelly-roll electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound via a strip-shaped separator.

5. The nonaqueous electrolyte secondary battery according to claim 4, wherein a width of the negative electrode active material layer in a winding axis direction of the jelly-roll electrode body is 20 cm or more.

6. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the nonaqueous electrolyte secondary battery includes a negative electrode tab group in which a plurality of the negative electrode tabs are stacked, and a negative electrode current collecting member to which the negative electrode tabs are electrically connected, and the negative electrode tab group is bent to be connected to the negative electrode current collecting member.

7. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the separator has an adhesive layer on both surfaces.

8. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the first region has a region that does not oppose the positive electrode active material layer. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the width direction of the negative electrode, the width of the region in the first region that is opposite the positive electrode is greater than the width of the region in the first region that is not opposite the positive electrode.

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