Nonaqueous electrolyte secondary battery

Abstract

In this nonaqueous electrolyte secondary battery, at least one of a positive electrode plate and a negative electrode plate has mixture layers that are formed on both surfaces of a core body. Both surfaces of the core body are provided with a first exposure part and a second exposure part, which have a rectangular shape or a trapezoidal shape, and in which the core body is exposed. Each of the exposure parts is formed only in a partial range in the short-side direction, inward, in the short-side direction, from one edge in the short-side direction in one electrode plate. When one electrode plate is deployed in a planar shape and viewed from the thickness direction, each exposure part has a first edge part that extends along the short-side direction, a second edge part that is positioned closer to a winding end side than the first edge part, and a third edge part that extends along the long-side direction or along a direction that is inclined with respect to the long-side direction. With respect to first corner parts that are sandwiched between the first edge parts and the third edge parts and second corner parts that are sandwiched between the second edge parts and the third edge parts, at least one pair of corner parts are out of alignment with each other in the short-side direction.

Description

Nonaqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery.

[0002] A nonaqueous electrolyte secondary battery includes an electrode assembly including a positive electrode plate, a negative electrode plate, and a separator between the positive and negative electrode plates, and a nonaqueous electrolyte housed in an outer can. For example, a cylindrical nonaqueous electrolyte secondary battery includes a wound electrode assembly in which the positive electrode plate and the negative electrode plate are spirally wound with the separator interposed therebetween. For example, Patent Document 1 describes a nonaqueous electrolyte secondary battery in which a positive electrode lead is welded to an uncoated region (exposed portion) of the positive electrode plate constituting the wound electrode assembly, where the positive electrode active material layer (positive electrode mixture layer) is absent within an area narrower than the width (transverse length) of the positive electrode plate. This reduces the area of ​​the uncoated region where the positive electrode active material layer peels off, which is said to contribute to increasing the capacity of the battery.

[0003] Japanese Patent Application Laid-Open No. 2003-68271

[0004] In nonaqueous electrolyte secondary batteries, the electrode assembly repeatedly expands and contracts within the outer can during charging and discharging. During this process, the positive and negative electrode plates expand and contract, resulting in high surface pressure between the electrode plates. In particular, in a wound electrode assembly, compressive stress in the winding direction is the greatest force acting on the electrode plates. For example, compressive stress acts inward on the positive electrode plate from both longitudinal ends corresponding to the winding direction of the electrode assembly. Meanwhile, in a configuration in which only a portion of the positive electrode plate in the transverse direction has an exposed portion where the positive electrode mixture layer is absent, as in Patent Document 1, it is conceivable to form exposed portions on both thickness-wise sides of the positive electrode plate so that they are positioned at the same position when viewed from the thickness direction. In this configuration, while the positive electrode mixture layer expands and contracts during charging and discharging, the positive electrode core including each exposed portion does not. This tends to result in large stress concentrations near the corners between the edges of each exposed portion along the transverse direction of the positive electrode plate and the edges along the longitudinal direction of the positive electrode plate. As a result, stress concentration acting on the positive electrode core from both sides in the thickness direction makes it more likely that the positive electrode plate will be damaged, such as by breakage of the positive electrode core. In the above, a case where an exposed portion is formed in a portion of the short side of the positive electrode plate has been described, but similar problems may occur when an exposed portion is formed in a portion of the short side of the negative electrode plate.

[0005] The nonaqueous electrolyte secondary battery according to the present disclosure is a nonaqueous electrolyte secondary battery including an electrode assembly in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, and at least one of the positive electrode plate and the negative electrode plate has a mixture layer formed on both sides of a long core body, and a first exposed portion having a rectangular or trapezoidal shape, where the core body is exposed, is provided in a longitudinally intermediate portion of a first surface of the core body corresponding to the winding direction of the electrode body, and a second exposed portion having a rectangular or trapezoidal shape, where the core body is exposed, is provided in a longitudinally intermediate portion of a second surface of the core body, and the first exposed portion and the second exposed portion are each formed in one of the electrode plates from one end edge in the lateral direction, corresponding to the winding axis direction of the electrode body, toward the inside in the lateral direction. and at least a portion of each electrode plate overlaps with the other in the thickness direction of the core body, and when one of the electrode plates is developed into a plane and viewed in the thickness direction, the first exposed portion and the second exposed portion each have a first edge portion along the short side direction, a second edge portion along the short side direction and located closer to the end of the winding than the first edge portion, a third edge portion along the long side direction or a direction oblique to the long side direction, a first corner portion sandwiched between the first edge portion and the third edge portion, and a second corner portion sandwiched between the second edge portion and the third edge portion, and at least one pair of corners of the pair of first corners and the pair of second corners of the first exposed portion and the second exposed portion are offset from each other in the short side direction.

[0006] According to the nonaqueous electrolyte secondary battery according to the present disclosure, damage to the electrode plate during charge and discharge can be suppressed, regardless of the configuration in which only part of the electrode plate in the short-side direction is exposed.

[0007] FIG. 1 is an axial cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment; FIG. 2 is a perspective view of a positive electrode plate according to an embodiment, exaggerating the range including the exposed portion of the positive electrode plate in the expanded state; (a) is a view of the positive electrode plate in the expanded state according to an embodiment, as viewed from the thickness direction, and (b) is an enlarged view of part A in (a); FIG. 3 is a perspective view of a positive electrode plate according to another embodiment, exaggerating the range including the exposed portion of the positive electrode plate in the expanded state; (a) is a view of the positive electrode plate in the expanded state according to another embodiment, as viewed from the thickness direction, and (b) is an enlarged view of part B in (a); FIG. 4 is a view corresponding to FIG. 3(b) in another embodiment; FIG. 5 is a view corresponding to FIG. 3(b) in another embodiment; FIG. 6 is a view corresponding to FIG. 3(b) in another embodiment.

[0008] Hereinafter, an example of an embodiment of a nonaqueous electrolyte secondary battery according to the present disclosure will be described in detail with reference to the drawings. Note that the nonaqueous electrolyte secondary battery according to the present disclosure is not limited to the embodiment described below.

[0009] In the following, a cylindrical battery in which a wound electrode assembly 14 is housed in a cylindrical outer can 16 with a bottom will be exemplified as a nonaqueous electrolyte secondary battery, but the outer can of the battery is not limited to a cylindrical outer can. The nonaqueous electrolyte secondary battery according to the present disclosure may be, for example, a prismatic battery equipped with a prismatic outer can, or a pouch-type battery equipped with an outer can made of a laminate sheet including a metal layer and a resin layer.

[0010] FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery 10 according to an embodiment. As shown in FIG. 1 , the nonaqueous electrolyte secondary battery 10 includes a positive electrode plate 11, a negative electrode plate 12, and a separator 13. The positive electrode plate 11 and the negative electrode plate 12 are wound with the separator 13 interposed therebetween to form an electrode assembly 14. The nonaqueous electrolyte secondary battery 10 also includes a cylindrical outer can 16 with a bottom that houses the electrode assembly 14, and a sealing member 17 that closes the opening of the outer can 16. The outer can 16 houses a nonaqueous electrolyte together with the electrode assembly 14. The outer can 16 has a groove 22 formed in its sidewall, and the sealing member 17 is supported by the groove 22 to close the opening of the outer can 16. Hereinafter, for convenience of explanation, the sealing member 17 side of the nonaqueous electrolyte secondary battery 10 will be referred to as the top, and the bottom side of the outer can 16 will be referred to as the bottom.

[0011] The nonaqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. The nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolytic solution), and may be a solid electrolyte using a gel polymer or the like. The nonaqueous electrolyte secondary battery 10 is preferably a lithium ion battery. The electrolyte salt may be, for example, LiBF ４ , LiPF ６ Examples of the non-aqueous solvent include esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine.

[0012] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP). From the viewpoint of suppressing a decrease in the charge-discharge cycle characteristics of a nonaqueous electrolyte secondary battery or improving input characteristics, the nonaqueous electrolyte preferably contains 5% by mass or more of FEC, and more preferably 5% by mass to 15% by mass of FEC, relative to the mass of the nonaqueous electrolyte.

[0013] Examples of the solid electrolyte include solid or gel polymer electrolytes and inorganic solid electrolytes. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. Examples of the matrix polymer include a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesin, acrylic resin, and polyether resin. Examples of the inorganic solid electrolyte include materials known in all-solid-state lithium ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0014] As described above, the electrode assembly 14 has a wound structure in which the positive electrode plate 11 and the negative electrode plate 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode plate 11, the negative electrode plate 12, and the separator 13 are all long, strip-shaped bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode plate 12 is formed to be slightly larger than the positive electrode plate 11 in order to prevent lithium deposition. That is, the negative electrode plate 12 is formed to be longer in both the longitudinal and lateral directions than the positive electrode plate 11. The separator 13 is formed to be at least slightly larger than the positive electrode plate 11, and, for example, two separators 13 are arranged to sandwich the positive electrode plate 11.

[0015] A positive electrode tab 20 and a negative electrode tab 21 are connected to the electrode body 14. The positive electrode tab 20 electrically connects the positive electrode plate 11 and the sealing body 17. The positive electrode tab 20 is provided in the longitudinal center of the positive electrode plate 11, at a position away from the winding start end and winding end end of the electrode body 14.

[0016] The negative electrode tab 21 is joined to a first core exposed portion (not shown) provided at the winding start end, which is one longitudinal end of the negative electrode plate 12 located on the winding start side of the negative electrode plate 12. In the example shown in Fig. 1 , the positive electrode tab 20 passes through the opening of the upper insulating plate 18 and extends toward the sealing body 17 and is joined to the underside of the sealing body 17, with the sealing body 17 serving as the positive electrode terminal. The negative electrode tab 21 passes through a through-hole in the annular lower insulating plate 19, is bent toward the hollow portion of the electrode body 14, and is connected to the inner bottom surface of the outer can 16 by welding or the like, with the outer can 16 serving as the negative electrode terminal.

[0017] The negative electrode plate 12 is disposed on the outermost peripheral surface of the electrode assembly 14, and a second core exposed portion 44 is provided where the surface of the negative electrode core 40 is exposed. The core exposed portion 44 abuts against the inner peripheral surface of the outer can 16. The core exposed portion 44 abuts against the inner peripheral surface of the outer can 16, which serves as the negative electrode terminal, thereby electrically connecting both longitudinal ends of the negative electrode plate 12 to the outer can 16 and ensuring good current collection. The core exposed portion 44 may be provided on a portion of the outermost peripheral surface of the electrode assembly 14, but is preferably provided over the entire outermost peripheral surface. For example, a portion where no negative electrode mixture layer is present is provided on both sides of the negative electrode core 40 over a length of at least one circumference of the electrode assembly 14 from the winding end of the negative electrode plate 12.

[0018] The positive electrode plate 11 includes a positive electrode core 30 and positive electrode mixture layers 31a, 31b formed on both sides of the core. Specifically, the positive electrode mixture layer 31a is formed on a first side of the positive electrode core 30, and the positive electrode mixture layer 31b is formed on a second side of the positive electrode core 30. The positive electrode core 30 may be made of a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode plate 11, or a film with such a metal disposed on the surface. The positive electrode mixture layers 31a, 31b preferably contain a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and are formed on both sides of the positive electrode core 30. The thickness of the positive electrode mixture layers 31a, 31b is, for example, 40 μm or more and 100 μm or less. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, or the like is used as the positive electrode active material. It is preferable that the positive electrode tab 20 be directly joined to the positive electrode core 30 by ultrasonic welding or the like.

[0019] The negative electrode plate 12 has a negative electrode core 40 and negative electrode mixture layers formed on both sides of the negative electrode core 40. The negative electrode core 40 can be made of a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode plate 12, or a film with such a metal disposed on the surface. The negative electrode mixture layers 41a, 41b contain a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). The thickness of the negative electrode mixture layers 41a, 41b is, for example, 40 μm or more and 100 μm or less. For example, graphite, a Si-containing material, or the like is used as the negative electrode active material. The negative electrode tab 21 is preferably directly bonded to the negative electrode core 40 by ultrasonic welding or the like.

[0020] The outer can 16 is a cylindrical metal container with a bottom. A gasket 28 is provided between the outer can 16 and the sealing body 17 to seal the interior of the battery. The outer can 16 has a groove 22 that supports the sealing body 17, formed, for example, by pressing the side surface from the outside. The groove 22 is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its top surface. The upper end of the outer can 16 is bent inward and crimped to the periphery of the sealing body 17.

[0021] The sealing body 17 has a structure in which, in order from the electrode body 14 side, a terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked. Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected to each other at their respective centers, and the insulating member 25 is interposed between their respective peripheral edges. When the internal pressure of the battery increases, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 toward the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure further increases, the upper valve body 26 breaks, and gas is discharged from the opening of the cap 27.

[0022] The configuration of the positive electrode plate 11 constituting the electrode body 14 will be described in detail below with reference to Figures 2 and 3. Figure 2 is a see-through perspective view of the positive electrode plate 11 in an expanded state, exaggerating the range including the exposed portions 33a and 33b of the positive electrode plate 11. Figure 3(a) is a view of the expanded positive electrode plate 11 as seen from the thickness direction, and Figure 3(b) is an enlarged view of portion A in Figure 3(a).

[0023] As described above, the positive electrode plate 11 has the positive electrode core 30 and the positive electrode mixture layers 31 a and 31 b formed on both sides of the positive electrode core 30 .

[0024] On the first surface (front side surface in FIGS. 2 and 3 ) of the positive electrode plate 11, a first exposed portion 33a in which the surface of the positive electrode core 30 is exposed is formed on one side in the short side direction of the positive electrode plate 11 (upper portion in FIGS. 2 and 3 ) in the center in the longitudinal direction (left-right direction in FIGS. 2 and 3 ) of the positive electrode plate 11. In FIG. 3 , the longitudinal direction of the positive electrode plate 11 is indicated by arrow α, and the short side direction of the positive electrode plate 11 is indicated by arrow β. The longitudinal direction of the positive electrode plate 11 corresponds to the winding direction of the electrode assembly 14, and the short side direction of the positive electrode plate 11 corresponds to the winding axis direction of the electrode assembly 14.

[0025] On the second surface (the back side surface in FIGS. 2 and 3 ) of the positive electrode plate 11, a second exposed portion 33b, in which the surface of the positive electrode core 30 is exposed, is formed on one side in the short-side direction of the positive electrode plate 11 in the longitudinal center of the positive electrode plate 11. That is, the first exposed portion 33a and the second exposed portion 33b are each formed only in a partial range in the short-side direction from one side edge in the short-side direction (the upper edge in FIGS. 2 and 3 ) of the positive electrode plate 11 toward the inside in the short-side direction. At least a portion of the first exposed portion 33a and the second exposed portion 33b overlap each other in the thickness direction of the positive electrode core 30.

[0026] Each exposed portion 33a, 33b has a rectangular shape when viewed from the thickness direction of the positive electrode plate 11. The exposed portions 33a, 33b are formed by not applying a positive electrode mixture slurry to the positive electrode core 30 and not providing a positive electrode mixture layer 31. Alternatively, the exposed portions 33a, 33b may be formed by peeling off a portion of the positive electrode mixture layer 31. In this manner, the two exposed portions 33a, 33b are formed so as to contact only one lateral edge of the positive electrode plate 11. Therefore, the positive electrode mixture layers 31a, 31b are present on the other lateral side of the two exposed portions 33a, 33b, thereby achieving a higher battery capacity than when exposed portions are formed along both lateral edges of the positive electrode plate 11. The positions of the exposed portions 33a, 33b are not limited to the longitudinal center of the positive electrode plate 11, but may be in a longitudinal middle portion spaced apart from both longitudinal ends of the positive electrode plate 11. For example, the exposed portions 33a, 33b may be formed at a position offset toward one end of the positive electrode plate 11 in the longitudinal direction, or at a plurality of positions spaced apart from each other in the longitudinal direction.

[0027] The positive electrode tab 20 shown in FIG. 1 is joined to one of the exposed portions 33a, 33b, for example, the first exposed portion 33a on the first surface of the positive electrode core 30. The positive electrode tab 20 is connected to one end of the positive electrode core 30 in the short-side direction, but not beyond the center of the short-side direction. This shortens the overlap length of the positive electrode tab 20 with the positive electrode core 30, thereby eliminating the positive electrode tab 20 from near the center of the winding axis direction of the electrode assembly 14. This makes it easier to prevent the positive electrode tab 20 from breaking through the separator or other components inside the battery, even when external impact or stress is applied to the battery. This improves the safety of the nonaqueous electrolyte secondary battery 10. Note that each exposed portion 33a, 33b may be formed in a range extending from one end of the positive electrode core 30 in the short-side direction beyond the center of the short-side direction.

[0028] 3 , when the positive electrode plate 11 is developed in a planar form and viewed in the thickness direction, the first exposed portion 33a has a first edge E1 and a second edge E2 that are spaced apart in the longitudinal direction and extend along the short side, and a third edge E3 that extends along the longitudinal direction. The first edge E1 is located at the start of the winding, and the second edge E2 is located at the end of the winding. Therefore, the second edge E2 is located closer to the end of the winding than the first edge E1.

[0029] On the other hand, when the positive electrode plate 11 is unfolded in a planar form and viewed in the thickness direction, the second exposed portion 33b has a first edge F1 and a second edge F2 that are spaced apart in the longitudinal direction and extend along the short side, and a third edge F3 that extends along the longitudinal direction. The first edge F1 is located at the start of the winding, and the second edge F2 is located at the end of the winding. Therefore, the second edge F2 is located closer to the end of the winding than the first edge F1. In Figure 3, the edges and points located on the back side of the positive electrode plate 11 are indicated by symbols in parentheses.

[0030] In this embodiment, points A1 and B1, which are corners between the first edges E1, F1 and the third edges E3, F3, and points A2 and B2, which are corners between the second edges E2, F2 and the third edges E3, F3, are offset from each other in the short-side direction. Points A1 and B1 correspond to first corners. Points A2 and B2 correspond to second corners. Specifically, the first edge E1 and the second edge E2 are longer in the short-side direction β than the first edge F1 and the second edge F2, respectively.

[0031] As a result, even when stress concentration tends to occur near the corners of the exposed portions 33 a, 33 b of each positive electrode mixture layer 31 a, 31 b when the positive electrode plate 11 repeatedly expands and contracts with charge and discharge of the nonaqueous electrolyte secondary battery 10, it is possible to shift the positions on both sides of the positive electrode plate 11 where the stress concentration is large from the overlapping positions in the thickness direction of the positive electrode plate 11. As a result, it is possible to shift the positions on both sides of the positive electrode plate 11 where the force acting near the corners of each exposed portion 33 a, 33 b in the positive electrode core 30 is large from the overlapping positions in the thickness direction of the positive electrode plate 11. Therefore, regardless of a configuration in which the positive electrode plate 11 has exposed portions only in a portion in the short side direction, stress concentration near the corners of each exposed portion 33 a, 33 b of the positive electrode plate 11 can be alleviated, thereby suppressing damage to the positive electrode plate 11, such as damage to the positive electrode core 30, during charge and discharge.

[0032] Furthermore, when the positive electrode plate 11 is unfolded in a plane and viewed in the thickness direction, the shortest distance in the short side direction between point A1, which is a corner of the first exposed portion 33a, and point B1, which is a corner of the second exposed portion 33b, is 0.5 mm or more. Similarly, when the positive electrode plate 11 is viewed in the thickness direction, the shortest distance in the short side direction between point A2, which is a corner of the first exposed portion 33a, and point B2, which is a corner of the second exposed portion 33b, is also 0.5 mm or more. This enhances the effect of suppressing damage to the positive electrode plate 11.

[0033] When the positive electrode plate 11 is unfolded in a planar state and viewed in the thickness direction, the first edge E1 and the second edge E2 of the first exposed portion 33a and the first edge F1 and the second edge F2 of the second exposed portion 33b are located at the same positions in the longitudinal direction α. ​​This reduces the amount of reduction in the positive electrode mixture layers 31a, 31b due to the formation of the exposed portions, thereby further increasing the capacity of the battery. This also increases the uniformity of the reaction between the positive electrode plate 11 and the negative electrode plate 12 on both sides of the positive electrode plate 11 in the thickness direction.

[0034] Fig. 4 is a perspective view of the positive electrode plate 11a in an expanded state according to another embodiment, exaggerating the range including the exposed portion of the positive electrode plate 11a. Fig. 5(a) is a view of the positive electrode plate 11a in an expanded state according to another embodiment, as seen from the thickness direction, and Fig. 5(b) is an enlarged view of part B in Fig. 5(a).

[0035] In this configuration, when the positive electrode plate 11a is viewed in the thickness direction, each exposed portion 34a, 34b has a trapezoidal shape. As shown in FIG. 5 , when the positive electrode plate 11a is unfolded in a planar form and viewed in the thickness direction, the first exposed portion 34a has a first edge E1a and a second edge E2a spaced apart in the longitudinal direction and extending along the short side, and a third edge E3a extending in a direction inclined relative to the longitudinal direction. The first edge E1a is longer than the second edge E2a. Meanwhile, the second exposed portion 34b has a first edge F1a and a second edge F2a spaced apart in the longitudinal direction and extending along the short side, and a third edge F3a extending in a direction inclined relative to the longitudinal direction. The second edge F2a is longer than the first edge F1a. As a result, the third edge E3a of the first exposed portion 34a and the third edge F3a of the second exposed portion 34b are inclined in opposite directions. In Figure 5, the edges and points located on the back side of the positive electrode plate 11a are indicated by symbols in parentheses.

[0036] In this example, points A1a and B1a, which are corners between the first edge portions E1a and F1a and the third edge portions E3a and F3a, and points A2a and B2a, which are corners between the second edge portions E2a and F2a and the third edge portions E3a and F3a, are offset from each other in the short-side direction. Points A1a and B1a correspond to first corners. Points A2a and B2a correspond to second corners. As a result, in this example, as with the configurations of FIGS. 1 to 3 , damage to the positive electrode plate 11a during charging and discharging can be suppressed, regardless of the configuration in which only a portion of the positive electrode plate 11a in the short-side direction is exposed.

[0037] Furthermore, when the positive electrode plate 11a is unfolded in a planar form and viewed in the thickness direction, the shortest distance in the short side direction between point A1a, which is a corner of the first exposed portion 34a, and point B1a, which is a corner of the second exposed portion 34b, is 0.5 mm or more. Similarly, when the positive electrode plate 11a is viewed in the thickness direction, the shortest distance in the short side direction between point A2a, which is a corner of the first exposed portion 34a, and point B2a, which is a corner of the second exposed portion 34b, is also 0.5 mm or more. This enhances the effect of suppressing damage to the positive electrode plate 11a during charging and discharging. Other configurations and functions of this example are similar to those of FIGS. 1 to 3.

[0038] FIG. 6 is a view corresponding to FIG. 3B of another example of the embodiment. In this configuration, the second exposed portion 35b of the positive electrode plate 11b is rectangular, while the first exposed portion 35a is trapezoidal. Specifically, the shape of the first exposed portion 35a is the same as the shape of the first exposed portion 34a in the configuration shown in FIGS. 4 and 5. Meanwhile, the shape of the second exposed portion 35b is the same as the shape of the second exposed portion 33b in the configuration shown in FIGS. 1 to 3. The longitudinal positions of the positive electrode plate 11c at the first edge portions E1b, F1b and second edge portions E2b, F2b of each exposed portion 35a, 35b are the same.

[0039] In this example, points A1b and B1b, which are corners between the first edge E1b, F1b and the third edge E3b, F3b, are located at different positions in the short-side direction. Meanwhile, points A2b and B2b, which are corners between the second edge E2b, F2b and the third edge E3b, F3b, are located at the same position in the short-side direction. Points A1b and B1b correspond to the first corners. Points A2b and B2b correspond to the second corners. Thus, if at least one pair of corners between the pair of corners on the first edge E1b, F1b side and the pair of corners on the second edge E2b, F2b side are offset from each other in the short-side direction, damage to the positive electrode plate 11b during charging and discharging can be suppressed, although the effect is lower than that of the configurations of the examples shown in Figures 1 to 5. In this example, the other configurations and functions are the same as those of Figures 1 to 3 or Figures 4 and 5.

[0040] FIG. 7 is a diagram corresponding to FIG. 3B in another example of the embodiment. In this configuration, when the positive electrode plate 11c is viewed in the thickness direction, the first exposed portion 36a has a first edge E1c and a second edge E2c that are spaced apart in the longitudinal direction of the positive electrode plate 11c and extend along the short side, and a third edge E3c that extends along the longitudinal direction. The first edge E1c and the second edge E2c are the same length. In this example, the corners of the first exposed portion 36a are not points, but are a straight line segment G1 connecting points A1c and A2c and a straight line segment G2 connecting points A3c and A4c. The straight line segment G1 corresponds to the first corner, and the straight line segment G2 corresponds to the second corner.

[0041] On the other hand, the second exposed portion 36b has a shape similar to that of the first exposed portion 36a, but the first edge F1c and the second edge F2c are shorter than the first edge E1c and the second edge E2c of the first exposed portion 36a, respectively. Therefore, when the positive electrode plate 11c is viewed in the thickness direction, the two corners of the second exposed portion 36b, i.e., the linear portions H1 and H2, are offset in the short direction from the linear portions G1 and G2 of the first exposed portion 36a, respectively. The linear portion H1 corresponds to the first corner, and the linear portion H2 corresponds to the second corner.

[0042] When viewed from the thickness direction of the positive electrode plate 11c, the shortest distance in the short side direction between the straight line portion G1 of the first exposed portion 36a and the straight line portion H1 of the second exposed portion 36b is 0.5 mm or more. When viewed from the thickness direction of the positive electrode plate 11c, the shortest distance in the short side direction between the straight line portion G2 of the first exposed portion 36a and the straight line portion H2 of the second exposed portion 36b is also 0.5 mm or more. In this example, the other configurations and functions are similar to those of FIGS. 1 to 3.

[0043] FIG. 8 is a diagram corresponding to FIG. 3B in another example of the embodiment. In this example, similar to the configuration in FIG. 6, the first exposed portion 37a of the positive electrode plate 11d is trapezoidal, and the second exposed portion 37b is rectangular. The first edge E1d and the second edge E2d of the first exposed portion 37a are aligned along the short-side direction of the positive electrode plate 11d. Meanwhile, the corner of the first exposed portion 37a between the first edge E1d and the third edge E3d is an arc-shaped curved portion J connecting points A1d and A3d. The curved portion J corresponds to the first corner.

[0044] When viewed from the thickness direction of the positive electrode plate 11d, a point B1d, which is a corner sandwiched between the first edge F1d and the third edge F3d of the second exposed portion 37b, and a curved portion J, which is a corner of the first exposed portion 37a, are offset from each other in the short-side direction. Point B1d corresponds to the first corner. In this example, the other configurations and functions are similar to those of FIG. 6.

[0045] As described in the above examples, in each exposed portion of the positive electrode plate, the corner between the first edge portion and the second edge portion may be a point, a straight line portion, or a curved line portion. In addition, in each of the above examples, only the pair of second corners of the pair of first corners and the pair of second corners of the first exposed portion and the second exposed portion may be configured to be offset from each other in the short-side direction.

[0046] In addition, in the above examples, the electrode plate having an exposed portion only in a portion in the short-side direction is described as a positive electrode plate, but the negative electrode plate may have an exposed portion only in a portion in the short-side direction on both sides in the thickness direction. In this configuration, damage to the negative electrode plate, such as damage to the negative electrode core during charge and discharge, can be suppressed, regardless of the configuration in which the negative electrode plate has an exposed portion only in a portion in the short-side direction.

[0047] The present disclosure will be further described by the following embodiments. Configuration 1: A nonaqueous electrolyte secondary battery including an electrode assembly in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, wherein at least one of the positive electrode plate and the negative electrode plate has a mixture layer formed on both sides of a long core body, a first exposed portion having a rectangular or trapezoidal shape, whereby the core body is exposed, is provided in a longitudinally intermediate portion on a first surface of the core body corresponding to the winding direction of the electrode body, and a second exposed portion having a rectangular or trapezoidal shape, whereby the core body is exposed, is provided in a longitudinally intermediate portion on a second surface of the core body, wherein the first exposed portion and the second exposed portion are each formed on one of the electrode plates in only a partial range in the transverse direction from one end edge in the transverse direction, corresponding to the winding axis direction of the electrode body, toward the inside in the transverse direction, and at least a portion of each exposed portion overlaps with each other in the thickness direction of the core body, a first exposed portion and a second exposed portion, the first exposed portion having a width of 1 / 2 mm or more, the second ... The present invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the non-aqueous electrolyte secondary battery, and to a method for manufacturing the non-aqueous electrolyte secondary battery, and to a method for manufacturing the non-aqueous electrolyte secondary battery, and

[0048] 10 Non-aqueous electrolyte secondary battery, 11, 11a to 11d Positive electrode plate, 12 Negative electrode plate, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode tab, 21 Negative electrode tab, 22 Grooved portion, 23 Terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core, 33a, 34a, 35a, 36a, 37a First exposed portion, 33b, 34b, 35b, 36b, 37b Second exposed portion, 31a, 31b Positive electrode mixture layer, 40 Negative electrode core, 41 Negative electrode mixture layer, 44 Second core exposed portion.

Claims

1. A nonaqueous electrolyte secondary battery comprising an electrode body in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, wherein at least one of the positive electrode plate and the negative electrode plate has a mixture layer formed on both sides of a long core body, a first exposed portion having a rectangular or trapezoidal shape exposing the core body is provided in a longitudinal middle portion of a first surface of the core body corresponding to the winding direction of the electrode body, and a second exposed portion having a rectangular or trapezoidal shape exposing the core body is provided in a longitudinal middle portion of a second surface of the core body, wherein the first exposed portion and the second exposed portion are each formed in only a part of the short side direction from one end edge in the short side direction corresponding to the winding axis direction of the electrode body toward the inside in the short side direction on one of the electrode plates, and at least a part of each exposed portion overlaps with each other in the thickness direction of the core body, a first exposed portion and a second exposed portion, when the one electrode plate is developed into a plane and viewed in a thickness direction, each of the first exposed portion and the second exposed portion has a first edge portion along the short side direction, a second edge portion along the short side direction and located on the winding end side of the first edge portion, a third edge portion along the long side direction or a direction inclined with respect to the long side direction, a first corner portion sandwiched between the first edge portion and the third edge portion, and a second corner portion sandwiched between the second edge portion and the third edge portion, and at least one pair of corners of the pair of first corners and the pair of second corners of the first exposed portion and the second exposed portion are offset from each other in the short side direction.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein when said one electrode plate is developed into a plane and viewed in the thickness direction, the shortest distance between said at least one pair of corners in the short side direction is 0.5 mm or more.

3. The nonaqueous electrolyte secondary battery according to claim 1, wherein, when the one electrode plate is developed into a plane and viewed in the thickness direction, the first edge portion and the second edge portion of the first exposed portion and the first edge portion and the second edge portion of the second exposed portion are each located at the same position in the longitudinal direction.

4. The nonaqueous electrolyte secondary battery according to claim 1, wherein the one electrode plate is the positive electrode plate.

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