Non-aqueous electrolyte secondary battery and method for manufacturing a non-aqueous electrolyte secondary battery

Abstract

Provided are a nonaqueous electrolyte secondary battery whereby damage to electrode bodies is suppressed and a production method therefor. The nonaqueous electrolyte secondary battery according to an embodiment of the present invention is provided with: an electrode body in which a first electrode and a second electrode that have different polarities are wound with a separator interposed therebetween; a nonaqueous electrolyte; an exterior can that houses the electrode body and the nonaqueous electrolyte, the exterior can being shaped as a bottomed cylinder; and a sealing body for sealing the opening of the exterior can. The first electrode has a core, a mixture layer formed on at least part of the surface of the core, and an exposed section of the core provided on one end on one side of the electrode body in the winding-axis direction. The exposed section has: an easily deformable section formed along the winding-axis direction of the electrode body; and an end surface section formed by the exposed section being curved along the easily deformable section, said end surface section being disposed on one end surface in the winding of the electrode body. The end section is joined to a current collector and the current collector is connected to the exterior can or the sealing body.

Description

[Technical Field]

[0001] This disclosure relates to a non-aqueous electrolyte secondary battery and a method for manufacturing a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries, in which wound electrode bodies, formed by overlapping and winding strip-shaped positive and negative electrodes, are housed in a bottomed cylindrical outer casing, have been widely used. Patent Document 1 discloses a technique to improve current collection efficiency and reduce electrical resistance within the battery by making the ends of the electrode cores protrude from the electrode bodies, pressing the tips of the ends to form a flat portion, and joining the flat portion to the current collector plate. Patent Document 2 discloses an improved technique of Patent Document 1, in which the base of the ends of the cores is coated with an insulating film to suppress buckling when forming the flat portion and to improve the insulation between the electrodes. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2000-294222 [Patent Document 2] Japanese Patent Publication No. 2006-32112 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, it is difficult to press the tip of the electrode end to form a uniform flat surface across the entire end of the electrode. As a result of diligent research by the present inventors, it has been found that if gaps are created between adjacent flat surfaces in the radial direction of the electrode body due to the formation of non-uniform flat surfaces, the laser light may reach the interior of the electrode body and damage components of the electrode body such as separators when the flat surfaces and the current collector plate are laser-bonded. The technologies disclosed in Patent Documents 1 and 2 do not take into account the damage to the electrode body during laser bonding, and there is still room for improvement.

[0005] The purpose of this disclosure is to provide a non-aqueous electrolyte secondary battery with suppressed electrode damage and a method for manufacturing the same. [Means for solving the problem]

[0006] A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure comprises an electrode body in which a first electrode and a second electrode having opposite polarities are wound with a separator between them, a non-aqueous electrolyte, a bottomed cylindrical outer container housing the electrode body and the non-aqueous electrolyte, and a sealing body that closes the opening of the outer container. The first electrode has a core body, a mixture layer formed on at least a part of the surface of the core body, and an exposed portion of the core body provided at one end of the electrode body in the winding axis direction, the exposed portion having a deformable portion formed along the winding direction of the electrode body, an end face portion formed by bending the exposed portion along the deformable portion being disposed on one end face of the electrode body in the winding axis direction, the end face portion being joined to a current collector plate, and the current collector plate being connected to the outer container or the sealing body.

[0007] A method for manufacturing a non-aqueous electrolyte secondary battery, as described in this disclosure, comprises an electrode body in which a first electrode and a second electrode having opposite polarities are wound with a separator between them, a non-aqueous electrolyte, a bottomed cylindrical outer container for housing the electrode body and the non-aqueous electrolyte, and a sealing body for closing the opening of the outer container. The first electrode has a core body, a composite layer formed on at least a part of the surface of the core body, and an exposed portion of the core body provided at one end in the winding axis direction of the electrode body. When winding the first electrode and the second electrode, the exposed portion is made to protrude from one end face in the winding axis direction of the electrode body, the exposed portion is bent along a deformable portion formed along the winding direction of the electrode body, the end face formed by the bending of the core body exposed portion is positioned, and the end face and the current collector plate are laser-bonded. [Effects of the Invention]

[0008] According to the non-aqueous electrolyte secondary battery described herein, damage to the electrode body can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1]It is an axial cross-sectional view of a non-aqueous electrolyte secondary battery which is an example of an embodiment. [Figure 2] It is a perspective view of a wound electrode body included in a non-aqueous electrolyte secondary battery which is an example of an embodiment. [Figure 3] In an example of an embodiment, it is a front view showing a negative electrode constituting an electrode body in an unfolded state. [Figure 4] It is a cross-sectional view taken along line A-A of FIG. 3. [Figure 5] It is a view corresponding to FIG. 4 in the negative electrode in the electrode body. [Figure 6] In a manufacturing method of a non-aqueous electrolyte secondary battery which is an example of an embodiment, it is a view showing a step of bending an exposed portion of a core body to form an inclined end face portion. [Figure 7] In another example of an embodiment, it is a front view showing a negative electrode constituting an electrode body in an unfolded state. [Figure 8] It is a cross-sectional view taken along line B-B of FIG. 7. [Figure 9] It is a view corresponding to FIG. 8 in the negative electrode in the electrode body. [Figure 10A] In a manufacturing method of a non-aqueous electrolyte secondary battery which is another example of an embodiment, it is a view showing a state where an exposed portion of a core body is bent along a second easily deformable portion. [Figure 10B] It is a view showing a state where an exposed portion of a core body is further bent from the state of FIG. 10A. [Figure 10C] It is a view showing a state where an exposed portion of a core body is further bent from the state of FIG. 10B to form a thick end face portion. [Figure 10D] It is a view showing a state where an exposed portion of a core body is bent along a first easily deformable portion from the state of FIG. 10C to incline an end face portion. [Figure 11] In another example of an embodiment, it is a view corresponding to FIG. 9.

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the non-aqueous electrolyte secondary battery 10 according to this disclosure will be described in detail with reference to the drawings. Note that if multiple embodiments or modifications are included below, it is intended from the outset that new embodiments may be constructed by appropriately combining their characteristic features. Furthermore, among the components described below, components not described in the independent claim indicating the highest-level concept are optional components and not essential components. In different embodiments, the same components are denoted by the same reference numerals in the drawings, and redundant explanations are omitted. Also, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings.

[0011] Figure 1 is an axial cross-sectional view of a non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. As shown in Figure 1, the secondary battery 10 comprises an electrode body 14, a non-aqueous electrolyte (not shown), a bottomed cylindrical outer casing 16 that houses the electrode body 14 and the non-aqueous electrolyte, and a sealing body 17 that closes the opening of the outer casing 16. The electrode body 14 includes a positive electrode 11 as an example of a first electrode, a negative electrode 12 as an example of a second electrode, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12. As will be described later, the electrode body 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound around each other via the separator 13. For the sake of explanation, in the following description, the direction along the axial direction of the outer casing 16 will be referred to as the "vertical direction or up-and-down direction," the side with the sealing body 17 will be referred to as "up," and the bottom 16d side of the outer casing 16 will be referred to as "down." The winding axis direction of the electrode body 14 substantially coincides with the axial direction of the outer casing 16. Furthermore, the direction perpendicular to the axial direction of the outer can 16 will be described as the "horizontal or radial direction," the radial center side of the outer can 16 will be described as the "inside," and the radial outer side will be described as the "outside."

[0012] Non-aqueous electrolytes include, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include carbonates, lactones, ethers, ketones, esters, etc., and two or more of these solvents can be used in mixture form. When using a mixture of two or more solvents, it is preferable to use a mixed solvent containing a cyclic carbonate and a linear carbonate. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used as cyclic carbonates, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), etc. can be used as linear carbonates. Examples of electrolyte salts include LiPF6, LiBF4, LiCF3SO3, etc., and mixtures thereof. The solubility of the electrolyte salt in the non-aqueous solvent is, for example, 0.5 mol / L to 2.0 mol / L.

[0013] The outer container 16 is a bottomed cylindrical metal container with one end (upper end) open in the axial direction. The outer container 16 has a shoulder portion 16a that protrudes radially inward at the open end, a grooved portion 16b that protrudes from the outside inward on the side, a side wall portion 16c, and a disc-shaped bottom portion 16d.

[0014] At the lower end face of the electrode body 14 housed in the outer casing 16, a negative electrode core exposed portion 34 protrudes and is bent, with the negative electrode core body 30 exposed from the negative electrode 12. The end face portion 38 of the negative electrode core exposed portion 34, which is located at the end face of the electrode body 14, is joined to the current collector plate 40 located below the electrode body 14, and the current collector plate 40 is connected to the bottom portion 16d, so that the outer casing 16 becomes the negative electrode terminal.

[0015] The outer shape of the current collector plate 40 is not particularly limited, but for example, it is a disc having a diameter approximately the same as the inner diameter of the outer casing 16. The current collector plate 40 may have ventilation holes. The thickness of the current collector plate 40 is preferably 0.1 mm to 0.7 mm, and more preferably 0.3 mm to 0.5 mm. In order to make the end face portion 38 of the negative electrode core exposed portion 34 come into approximately uniform contact with the current collector plate 40, the thickness of the current collector plate 40 is preferably 0.1 mm or more. Also, if the thickness of the current collector plate 40 is 0.7 mm or less, the current collector plate 40 and the end face portion 38 can be joined with appropriate strength.

[0016] The material of the current collector plate 40 is not particularly limited as long as it is conductive, but it is preferable that it be made of the same material as the outer casing 16. This makes it easier to connect the current collector plate 40 and the outer casing 16 by welding. The material of the current collector plate 40 and the outer casing 16 is, for example, carbon steel with nickel plating.

[0017] The shoulder portion 16a of the outer can 16 is formed when the open end of the outer can 16 is folded inward and the peripheral edge of the sealing body 17 is crimped. The sealing body 17 is crimped and fixed between the shoulder portion 16a and the grooved portion 16b via a gasket 28.

[0018] The internal space of the secondary battery 10 is sealed by a gasket 28, which is a resin annular member, sealing the space between the outer casing 16 and the sealing body 17. The gasket 28 is sandwiched between the outer casing 16 and the sealing body 17, insulating the sealing body 17 from the outer casing 16. In other words, the gasket 28 serves as both a sealing material to maintain airtightness inside the battery and an insulating material to insulate the outer casing 16 and the sealing body 17.

[0019] The sealing body 17 is a disc-shaped member equipped with a current interruption mechanism. The sealing body 17 has a structure in which a terminal plate 23, an insulating plate 24, and a rupture plate 27 are stacked in order from the electrode body 14 side. The positive electrode lead 20 connected to the positive electrode 11 is connected by welding or the like to the lower surface of the terminal plate 23, which is the bottom plate of the sealing body 17, through a through hole in the insulating plate 18, and the rupture plate 27, which is the top plate of the sealing body 17 and is electrically connected to the terminal plate 23, becomes the positive electrode terminal. The terminal plate 23 has a ventilation hole 23a and a thin-walled portion 23b that is disconnected when the internal pressure of the battery exceeds a predetermined threshold.

[0020] The rupture plate 27 is positioned opposite the terminal plate 23, with an insulating plate 24 in between. The insulating plate 24 has an opening for connecting the terminal plate 23 and the rupture plate 27, and a ventilation hole 24a in the portion that overlaps with the ventilation hole 23a of the terminal plate 23. The rupture plate 27 has a valve portion that deforms to interrupt the current path when the internal pressure of the battery exceeds a predetermined threshold, and the valve portion is connected to the central part of the terminal plate 23 by welding or the like through the opening in the insulating plate 24. If the internal pressure of the battery rises further, the valve portion will rupture, forming a gas outlet. The insulating plate 24 insulates the terminal plate 23 and the rupture plate 27 in all portions except the central connection portion.

[0021] In the example shown in Figure 1, a positive electrode lead 20 is extended from the positive electrode 11 and connected to the sealing body 17. However, the example is not limited to this, and for example, a current collector plate may be placed above the electrode body 14, and the exposed portion of the positive electrode core, which is provided at one end in the width direction of the positive electrode 11, may be joined to the lower surface of the current collector plate, and the positive electrode lead may be extended from the upper surface of the current collector plate and connected to the sealing body 17. Alternatively, if the positive electrode core is joined to the current collector plate as described above, a negative electrode lead may be extended from the negative electrode 12 and connected to the outer casing 16.

[0022] Next, the electrode body 14 will be described with reference to Figure 2. Figure 2 is a perspective view of the electrode body 14. As described above, the electrode body 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all formed in a strip shape and are wound in a spiral shape around a winding core arranged along the winding axis, resulting in them being alternately stacked in the radial direction of the electrode body 14.

[0023] The negative electrode 12 contained in the electrode body 14 is generally formed larger than the positive electrode 11 in order to prevent lithium deposition on the negative electrode 12. Specifically, the width of the negative electrode 12 is greater than the width of the positive electrode 11. Also, the longitudinal length of the negative electrode 12 is greater than the longitudinal length of the positive electrode 11. As a result, in the electrode body 14, at least the portion of the positive electrode 11 where the positive electrode mixture layer is formed is positioned opposite the portion of the negative electrode 12 where the negative electrode mixture layer is formed, via the separator 13.

[0024] The positive electrode 11 comprises a positive electrode core and a positive electrode mixture layer formed on at least a portion of the surface of the positive electrode core. The positive electrode mixture layer is formed on at least one of the inner and outer circumferences of the positive electrode core, and preferably covers the entire surface of both sides of the positive electrode core, excluding the exposed portion described later. For the positive electrode core, for example, a metal foil such as aluminum, or a film with the metal arranged on its surface, can be used. The thickness of the positive electrode core is, for example, 10 μm to 30 μm.

[0025] The positive electrode mixture layer includes, for example, a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, by coating both sides of a positive electrode core with a positive electrode mixture slurry containing the positive electrode active material, conductive agent, binder, and a solvent such as N-methyl-2-pyrrolidone (NMP), drying it, and then rolling it.

[0026] Examples of positive electrode active materials included in the positive electrode mixture layer include lithium transition metal oxides containing transition metal elements such as Co, Mn, and Ni. Lithium transition metal oxides include, for example, Li x CoO2, Li x KiO2, Li xMnO2, Li x Co y Ni 1-y O2, Li x Co y M 1-y O z , Li x Ni 1-y M y O z , Li x Mn2O4, Li x Mn 2-y M y O4, LiMPO4, Li2MPO4F (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B; 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3). These may be used alone or in combination of multiple kinds. In terms of achieving high capacity of the non-aqueous electrolyte secondary battery, the cathode active material is Li x NiO2, Li x Co y Ni 1-y O2, Li x Ni 1-y M y O z (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B; 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3), etc., and it is preferable to contain lithium nickel composite oxides such as these.

[0027] Examples of the conductive agent contained in the cathode mixture layer include carbon-based particles such as carbon black (CB), acetylene black (AB), ketjen black, carbon nanotube (CNT), graphene, and graphite. These may be used alone or in combination of two or more kinds.

[0028] Examples of binders included in the positive electrode mixture layer include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These may be used individually or in combination of two or more types.

[0029] The exposed positive electrode core portion is the part of the positive electrode core whose surface is not covered by the positive electrode mixture layer, and is preferably provided on both sides of the positive electrode 11 so as to overlap in the thickness direction of the positive electrode 11. The exposed positive electrode core portion is provided, for example, at a position approximately equidistant from the inner and outer ends of the electrode body 14 from the viewpoint of current collection. By connecting the positive electrode lead 20 to the exposed positive electrode core portion provided at such a position, when the electrode body 14 is wound, the positive electrode lead 20 is positioned to protrude upward from the axial end face at approximately the radial center of the electrode body 14. The exposed positive electrode core portion is provided, for example, by intermittent coating, in which the positive electrode mixture slurry is not applied to a part of the positive electrode core.

[0030] The negative electrode 12 comprises a negative electrode core 30, a negative electrode mixture layer 32 formed on at least a portion of the surface of the negative electrode core 30, and a negative electrode core exposed portion 34 provided at one end in the width direction. The negative electrode mixture layer 32 is formed on at least one of the inner and outer circumferences of the negative electrode core 30, and preferably forms on the entire surface of both sides of the negative electrode core 30, excluding the negative electrode core exposed portion 34 described later. For example, a metal foil such as copper, or a film with the metal arranged on its surface, can be used for the negative electrode core. The thickness of the negative electrode core is, for example, 5 μm to 30 μm.

[0031] The negative electrode mixture layer 32 includes, for example, a negative electrode active material and a binder. The negative electrode 12 can be manufactured, for example, by coating both sides of the negative electrode core 30 with a negative electrode mixture slurry containing the negative electrode active material, a binder, and a solvent such as water, drying it, and then rolling it.

[0032] The negative electrode active material contained in the negative electrode mixture layer 32 is not particularly limited as long as it can reversibly intercept and release lithium ions. For example, carbon-based materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or alloys and oxides containing these can be used.

[0033] The negative electrode active material may include carbon-based materials and silicon-based materials. Examples of silicon-based materials include Si, Si-containing alloys, and SiO2. x Examples include silicon oxides (where x is 0.8 to 1.6). Silicon-based materials are negative electrode active materials that can improve battery capacity compared to carbon-based materials. From the viewpoint of improving battery capacity and suppressing the deterioration of charge-discharge cycle characteristics, the content of silicon-based materials in the negative electrode active material is preferably 3% by mass or more relative to the mass of the negative electrode active material. The upper limit of the silicon-based material content is, for example, 20% by mass.

[0034] Examples of binders included in the negative electrode mixture layer 32 include styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethylcellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., or partially neutralized salts), and polyvinyl alcohol (PVA). These may be used individually or in combination of two or more types.

[0035] The exposed negative electrode core portion 34 is the portion of the negative electrode core 30 whose surface is not covered by the negative electrode mixture layer 32, and is preferably provided on both sides of the negative electrode 12 so as to overlap in the thickness direction of the negative electrode 12.

[0036] As shown in Figure 2, the exposed negative electrode core portion 34 protrudes from one end face in the winding axis direction of the electrode body 14 immediately after winding. That is, an exposed negative electrode core portion 34 of the exposed negative electrode core 30 is formed at one end in the width direction (axial direction) of the negative electrode 12, and at the end on the side where the exposed negative electrode core portion 34 is formed, the negative electrode 12 protrudes beyond the separator 13 from the end face of the electrode body 14. The exposed negative electrode core portion 34 is formed with approximately the same width along the winding direction, and it is preferable that the boundary line between the negative electrode mixture layer 32 and the exposed negative electrode core portion 34 is sandwiched between the separator 13.

[0037] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably polyolefin resins such as polyethylene and polypropylene, or cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer may be formed on the surface of the separator 13. The thickness of the separator is, for example, 10 μm to 50 μm.

[0038] Next, with reference to Figures 3 to 5, the shape of the exposed negative electrode core portion 34 protruding from the electrode body 14 immediately after winding will be described. Figure 3 is a front view showing the negative electrode 12 constituting the electrode body 14 in an unfolded state in an example of an embodiment. Figure 4 is a cross-sectional view along line AA in Figure 3, and Figure 5 is a diagram of the negative electrode 12 in the electrode body 14 corresponding to Figure 4.

[0039] As shown in Figure 3, the exposed negative electrode core portion 34 has a deformable portion 36 formed along the winding direction of the electrode body 14. In the example shown in Figure 3, the deformable portion 36 is formed continuously. The deformable portion 36 may also be formed discontinuously, for example, in the shape of a dashed line or a dotted line. In addition, in the example shown in Figure 3, the deformable portion 36 is straight, but it may have a curved portion if the negative electrode core 30 can be bent along the deformable portion 36 as will be described later.

[0040] In Figure 3, the axial length of the exposed negative electrode core portion 34 is, for example, 2 mm to 20 mm, and the axial length of the end face portion 38 is approximately the same as the length from the easily deformable portion 36 to the tip of the exposed negative electrode core portion 34, for example, 1 / 3 to 2 / 3 times the axial length of the exposed negative electrode core portion 34.

[0041] In this embodiment, as shown in Figure 4, the easily deformable portion 36 is a groove. The depth of the groove is preferably 1 / 5 to 2 / 3 times the thickness of the negative electrode core 30, and more preferably 1 / 3 to 1 / 2 times the thickness of the negative electrode core 30. The width of the groove is preferably, for example, 1 / 2 to 3 / 2 times the depth of the groove.

[0042] The cross-sectional shape of the negative electrode 12 changes from the shape shown in Figure 4 to the shape shown in Figure 5 when it is wound around the electrode body 14. Immediately after winding, the exposed negative electrode core portion 34 of the electrode body 14 has an end face portion 38 formed by bending along the easily deformable portion 36. As a result, when the end face portions 38 are pressed against the current collector plate 40, the direction in which the end face portions 38 face

[0043] Preferably, the end face portion 38 is formed such that the negative electrode core body exposed portion 34 is bent radially inward of the electrode body 14 along the easily deformable portion 36. This makes it easier to house the electrode body 14 in the outer can 16. If the easily deformable portion 36 is a groove, the end face portion 38 is formed at an angle toward the surface having the groove. The angle θ showing the inclination of the end face portion 38 in Figure 5 is, for example, 5° to 90°.

[0044] Figure 6 shows the process of bending the exposed negative electrode core portion 34 to form the end face portion 38. The X-axis direction indicates the axial direction in the electrode body 14, and the Y-axis direction indicates the winding direction in the electrode body 14. The negative electrode 12 moves in the + direction of the Y-axis relative to the guide rail 45. The inclination angle of the slope provided on the upper surface of the guide rail 45 increases from the - direction to the + direction of the Y-axis, and does not change after reaching a predetermined size. The negative electrode core 30 is located on the guide rail 45 and deforms along the shape of the upper surface of the guide rail 45 so as to bend along the easily deformable portion 36.

[0045] Next, with reference to Figures 7 to 9, the end face portion 138 in another example of the embodiment will be described. Figure 7 is a front view showing the negative electrode 12 constituting the electrode body 14 in an unfolded state in another example of the embodiment. Figure 8 is a cross-sectional view along the line BB in Figure 7, and Figure 9 is a diagram of the negative electrode 12 in the electrode body 14 corresponding to Figure 8.

[0046] As shown in Figure 7, the exposed negative electrode core portion 34 has a first easily deformable portion 36a and a second easily deformable portion 36b formed along the winding direction of the electrode body 14. The first easily deformable portion 36a and the second easily deformable portion 36b may be continuous or discontinuous. Furthermore, the first easily deformable portion 36a and the second easily deformable portion 36b are not limited to straight lines but may include curves.

[0047] In Figure 7, the axial length of the exposed negative electrode core portion 34 is, for example, 3 mm to 30 mm. The axial length of the end face portion 138 is approximately the same as the distance between the first easily deformable portion 36a and the second easily deformable portion 36b, and the length from the second easily deformable portion 36b to the tip of the exposed negative electrode core portion 34, and is, for example, 1 / 5 to 1 / 2 times the axial length of the exposed negative electrode core portion 34.

[0048] In this embodiment, as shown in Figure 8, the first easily deformable portion 36a and the second easily deformable portion 36b are grooves. The depth of the first easily deformable portion 36a is, for example, approximately the same as the depth of the second easily deformable portion 36b. The depth of the first easily deformable portion 36a and the second easily deformable portion 36b is preferably 1 / 5 to 2 / 3 times the thickness of the negative electrode core body 30, and more preferably 1 / 3 to 1 / 2 times the thickness of the negative electrode core body 30. The width of the first easily deformable portion 36a is, for example, approximately the same as the width of the second easily deformable portion 36b. The width of the first easily deformable portion 36a and the second easily deformable portion 36b is, for example, preferably 1 / 2 to 3 / 2 times the depth of the groove.

[0049] When the negative electrode 12 is wound around the electrode body 14, it is formed from the cross-sectional shape shown in Figure 8 to the cross-sectional shape shown in Figure 9. The exposed portion 34 of the negative electrode core is folded back along the second easily deformable portion 36b and has an end face portion 138 formed by bending along the first easily deformable portion 36a. By folding back at the second easily deformable portion 36b, the end face portion 138 has a thickness equivalent to twice that of the negative electrode core 30, and the output of the laser light irradiated when the end face portion 138 is laser-bonded to the current collector plate 40 can be increased.

[0050] Figures 10A to 10D show an example of the process of bending the exposed negative electrode core portion 34 to form the end face portion 138. First, as shown in Figure 10A, the exposed negative electrode core portion 34 is bent along the second easily deformable portion 36b. Furthermore, the exposed negative electrode core portion 34 is bent from the state in Figure 10A through the state in Figure 10B to the state in Figure 10C to form the thick end face portion 138. Finally, from the state in Figure 10C, the exposed negative electrode core portion 34 is bent along the first easily deformable portion 36a to incline the end face portion 138 as shown in Figure 10D. The shape of the guide rail 145 changes sequentially in the Y-axis direction as shown in Figures 10A to 10D.

[0051] Figure 11 shows the end face portion 138 in another example of the embodiment. In this example, the end face portion 138 further includes an insertion plate 50 inside the end face portion 238 in Figure 9. As a result, the end face portion 238 has a thickness of more than twice the thickness of the negative electrode core body 30, and the output of the laser beam irradiated when laser bonding the end face portion 238 to the current collector plate 40 can be further increased.

[0052] The material of the insertion plate 50 is, for example, metal. In the case of the negative electrode 12, the material of the insertion plate 50 is preferably Ni from the viewpoint of weldability with the negative electrode core 30. From the viewpoint of workability, the thickness of the insertion plate 50 is preferably greater than the thickness of the core that encloses the insertion plate 50. The thickness of the insertion plate 50 is, for example, 10 μm to 50 μm. When using the insertion plate 50, the core can be bent along the edge of the insertion plate 50, so the portion of the exposed negative electrode core 34 that contacts the edge of the insertion plate 50 may be made into an easily deformable portion 36. In this case, grooves as shown in Figures 7 and 8 are unnecessary. [Examples]

[0053] The present disclosure will be further illustrated below with reference to examples, but the present disclosure is not limited to these examples.

[0054] [Fabrication of the positive electrode] A cathode slurry was prepared by mixing lithium nickel composite oxide as the cathode active material, polyvinylidene fluoride as a binder, and acetylene black as a conductive agent, and adding an appropriate amount of N-methyl-2-pyrrolidone (NMP). The cathode slurry was applied to both sides of a cathode core made of aluminum foil, excluding the connection portion of the cathode lead, and the coating was dried. After rolling the dried coating to a predetermined thickness using a roller, the cathode was cut to a predetermined size to produce the cathode, and an aluminum cathode lead was welded to the connection portion.

[0055] [Fabrication of the negative electrode] A copper foil with a thickness of 8 μm was cut into strips, and a linear groove with a width of 4 μm and a depth of 4 μm was imprinted on one side of the copper foil along the longitudinal direction to prepare a negative electrode core. In addition, easily graphitizable carbon as the negative electrode active material, polyvinylidene fluoride as a binder, and carboxymethyl cerose as a thickener were mixed, and an appropriate amount of water was added to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was applied to both sides of the negative electrode core, excluding the areas corresponding to the exposed portion of the negative electrode core, and the coating was dried. After rolling the dried coating to a predetermined thickness using a roller, the negative electrode was cut to a predetermined size to produce a negative electrode. The produced negative electrode had the same configuration as the embodiment shown in Figure 3, with an axial length of the exposed portion of the negative electrode core being 4 mm, and a length of 2 mm from the bottom end of the negative electrode mixture layer to the groove.

[0056] [Fabrication of electrode bodies] The electrode body was fabricated by winding the positive and negative electrodes via a polyolefin resin separator, with the negative electrode core exposed portion (negative electrode core) protruding from one end face in the winding axis direction of the electrode body. Furthermore, during the winding of the electrode body, the negative electrode core exposed portion was bent approximately 30° on the guide rail from the groove to the tip to form a 2mm long end face. The negative electrode core had the same shape as the example shown in Figure 5.

[0057] [Laser bonding between the end face and the current collector] A disc-shaped nickel-plated carbon steel plate with a thickness of 0.4 mm was used as the current collector plate. The end face on the side where the negative electrode core of the electrode body protruded was pressed against the current collector plate, and a laser beam was irradiated from the current collector plate side while scanning in a straight line, thereby laser bonding the current collector plate and the end face. Laser bonding was performed at a total of four locations on the current collector plate, each at a 90-degree angle.

[0058] [Evaluation of electrode damage] Cross-sectional observation of the laser-bonded area was performed using an X-ray CT scanner (Shimadzu Corporation, SMX-225CT FPD HR). CT images were acquired at 12 locations to allow for observation of the entire welded area. Damage was determined if any traces of burning of separators or other materials were observed at any of the imaging locations, and the presence or absence of damage was evaluated.

[0059] <Example 2> In the fabrication of the negative electrode, in the same configuration as the embodiment shown in Figure 7, two straight grooves (width 4 μm, depth 4 μm) were formed by imprinting on the exposed portion of the negative electrode core, which had an axial length of 6 mm, at a 2 mm interval. In the fabrication of the electrode body, the electrode body was evaluated for damage in the same manner as in Example 1, except that the electrode body was folded back from the groove on the tip side to the tip on the guide rail, and then bent at approximately 30° at the groove on the base side to form a thick end face portion with a length of 2 mm. The negative electrode core had the same shape as the example shown in Figure 9.

[0060] <Example 3> In the fabrication of the negative electrode, a Ni metal plate with a width of 1.5 mm and a thickness of 30 μm was placed between two grooves. In the fabrication of the electrode body, the metal plate was wrapped in the negative electrode core when the tip of the electrode was folded back from the groove on the guide rail. Except for these differences, the electrode body damage was evaluated in the same manner as in Example 2. The negative electrode core had the same shape as the example shown in Figure 11.

[0061] The evaluation results for Examples 1-3 are shown in Table 1. Table 1 also includes the characteristics of the negative electrode core for each example.

[0062] [Table 1]

[0063] In all embodiments, no damage to the electrode body was observed. Therefore, it can be seen that damage to the electrode body can be suppressed by having an end face portion formed by bending along an easily deformable portion formed along the winding direction of the electrode body, where the exposed negative electrode core portion protruding from one end face in the winding direction of the electrode body is located. [Explanation of symbols]

[0064] 10 Secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer casing, 16a Shoulder section, 16b Grooved section, 16c Side wall section, 16d Bottom section, 17 Sealing body, 18 Insulating plate, 20 Positive electrode lead, 23 Terminal plate, 23a Ventilation hole, 23b Thin-walled section, 24 Insulating plate, 24a Ventilation hole, 27 Rupture plate, 28 Gasket, 30 Negative electrode core, 32 Negative electrode mixture layer, 34 Negative electrode core exposed section, 36 Easily deformable section, 36a First easily deformable section, 36b Second easily deformable section, 38, 138, 238 End face section, 40 Current collector plate, 45, 145 Guide rail, 50 Insertion plate

Claims

1. A non-aqueous electrolyte secondary battery comprising an electrode body in which a first electrode and a second electrode having opposite polarities are wound with a separator between them, a non-aqueous electrolyte, a bottomed cylindrical outer container housing the electrode body and the non-aqueous electrolyte, and a sealing body that closes the opening of the outer container, The first electrode comprises a core body, a composite layer formed on at least a portion of the surface of the core body, and an exposed portion of the core body provided at one end of the electrode body in the winding axis direction. The exposed portion has a first easily deformable portion formed along the winding direction of the electrode body, and a second easily deformable portion formed along the winding direction of the electrode body at a position away from the first easily deformable portion in the winding axis direction of the electrode body. An end face portion is provided on one end face of the electrode body in the winding axis direction, where the exposed portion is formed by bending along the first easily deformable portion and the second easily deformable portion. The end face portion is joined to the current collector plate. The current collector plate is connected to the outer casing or the sealing body of a non-aqueous electrolyte secondary battery.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the exposed portion is bent radially inward along the first easily deformable portion and the second easily deformable portion of the electrode body.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the first electrode is a negative electrode.

4. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the first easily deformable portion and the second easily deformable portion are grooves.

5. The non-aqueous electrolyte secondary battery according to claim 4, wherein the grooves are formed continuously.

6. The non-aqueous electrolyte secondary battery according to claim 4, wherein the grooves are formed discontinuously.

7. A method for manufacturing a non-aqueous electrolyte secondary battery comprising: an electrode body in which a first electrode and a second electrode having opposite polarities are wound with a separator between them; a non-aqueous electrolyte; a bottomed cylindrical outer container housing the electrode body and the non-aqueous electrolyte; and a sealing body that closes the opening of the outer container, The first electrode comprises a core body, a composite layer formed on at least a portion of the surface of the core body, and an exposed portion of the core body provided at one end of the electrode body in the winding axis direction. A method for manufacturing a non-aqueous electrolyte secondary battery, comprising winding the first electrode and the second electrode, wherein the exposed portion is made to protrude from one end face in the winding axis direction of the electrode body, and while the exposed portion is in contact with an inclined surface that has a larger inclination angle in one direction of the winding direction of the electrode body, the first electrode is moved in one direction of the winding direction of the electrode body, thereby bending the exposed portion along a deformable portion formed along the winding direction of the electrode body, arranging the end face formed by the bending of the exposed portion, and laser bonding the end face to a current collector plate.

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