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

Abstract

The object of the present invention is to provide a non-aqueous electrolyte secondary battery that can suppress internal short circuits of the battery caused by external impacts in either a fully charged state or a non-fully charged state. The non-aqueous electrolyte secondary battery as one embodiment of the present invention is characterized in that it has a wound electrode body in which a positive electrode and a negative electrode are wound with a separator therebetween and a battery case for storing the electrode body, the positive electrode has a positive electrode collector and a positive electrode mixture layer formed on at least one surface of the positive electrode collector, and the separator has a normal portion and a plastic deformation portion having a higher puncture strength than the normal portion.

Description

Technical Field

[0001] The present invention relates to a nonaqueous electrolyte secondary battery and a method for producing the nonaqueous electrolyte secondary battery. Background Art

[0002] A non-aqueous electrolyte secondary battery in which a wound electrode body formed by winding a strip-shaped positive electrode and a negative electrode with a separator interposed therebetween is housed in a metal battery case has been widely used. Patent document 1 discloses a non-aqueous electrolyte secondary battery that suppresses thermal runaway of the battery caused by external impact in a fully charged state by using a separator that satisfies a predetermined tensile fracture strength.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-139865 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, Patent Document 1 does not examine the effects on a non-aqueous electrolyte secondary battery in a state of being partially charged when the battery is subjected to an external impact.

[0008] An object of the present invention is to provide a nonaqueous electrolyte secondary battery capable of suppressing internal short circuit of the battery due to external impact in both a fully charged state and a non-fully charged state.

[0009] Means for solving problems

[0010] A non-aqueous electrolyte secondary battery as one embodiment of the present invention is characterized in that it comprises: a wound electrode body formed by winding a positive electrode and a negative electrode with a separator between them, and a battery case for accommodating the electrode body, the positive electrode having a positive electrode collector and a positive electrode mixture layer formed on at least one surface of the positive electrode collector, and the separator having a normal portion and a plastic deformation portion having a higher puncture strength than the normal portion.

[0011] A method for manufacturing a non-aqueous electrolyte secondary battery as one embodiment of the present invention is characterized in that the non-aqueous electrolyte secondary battery comprises a wound electrode body in which a positive electrode and a negative electrode are wound with a separator between them, and a battery case for housing the electrode body, and when the positive electrode and the negative electrode are wound with the separator between them, a portion of the separator is stretched along the winding direction to cause it to be plastically deformed.

[0012] Effects of the Invention

[0013] According to the nonaqueous electrolyte secondary battery of the present invention, the battery can withstand external impact and suppress internal short circuit in both the fully charged state and the partially charged state. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery as an example of an embodiment.

[0015] Figure 2 yes Figure 1 A perspective view of a wound electrode body of a nonaqueous electrolyte secondary battery shown.

[0016] Figure 3 It is a longitudinal cross-sectional view of a positive electrode in one example of the embodiment.

[0017] Figure 4 It is a plan view showing the opposing relationship between the positive electrode and the separator in the electrode body in one example of the embodiment.

[0018] Figure 5 It is a front view showing the structure of a winding device for an electrode body as an example of an embodiment.

[0019] Figure 6 Yes means Figure 5 A side view of the structure of the stretching section of the winding device is shown.

[0020] Figure 7 In another example of the implementation mode Figure 5 The corresponding figure. DETAILED DESCRIPTION

[0021] Hereinafter, an example of an embodiment of the nonaqueous electrolyte secondary battery of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific shapes, materials, numerical values, directions, etc. are used to easily understand the illustrations of the present invention and can be appropriately changed according to the specifications of the nonaqueous electrolyte secondary battery. In addition, in the following description, in the case of including a plurality of embodiments and variations, it is envisioned at the beginning of the application to appropriately combine and use their characteristic parts.

[0022] Figure 1 FIG. 2 is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery 10 as an example of an embodiment. Figure 1As shown, in the non-aqueous electrolyte secondary battery 10, the electrode body 14 and the non-aqueous electrolyte (not shown) are contained in the battery case 15. As a non-aqueous solvent (organic solvent) of the non-aqueous electrolyte, carbonates, lactones, ethers, ketones, esters, etc. can be used, and two or more of these solvents can be mixed and used. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, and mixed solvents of cyclic carbonates and chain carbonates can be used. As an electrolyte salt of a non-aqueous electrolyte, LiPF6, LiBF4, LiCF3SO3, etc. and mixtures thereof can be used. The amount of electrolyte salt dissolved relative to the non-aqueous solvent can be set to 0.5 to 2.0 mol / L, for example.

[0023] The battery case 15 is composed of an outer body 16 and a sealing body 17. Insulating plates 18 and 19 are respectively provided above and below the electrode body 14. The positive lead 20 extends to the sealing body 17 side through the through hole of the insulating plate 18 and is welded to the bottom plate of the sealing body 17, that is, the lower surface of the filter 23. In the non-aqueous electrolyte secondary battery 10, the top plate of the sealing body 17, that is, the cover 27 electrically connected to the filter 23 becomes the positive terminal. On the other hand, the negative lead 21 extends to the bottom side of the outer body 16 through the through hole of the insulating plate 19 and is welded to the bottom inner surface of the outer body 16. In the non-aqueous electrolyte secondary battery 10, the outer body 16 becomes the negative terminal. When the negative lead 21 is provided near the outer end of the roll, the negative lead 21 extends to the bottom side of the battery case 15 through the outside of the insulating plate 18 and is welded to the bottom inner surface of the battery case 15.

[0024] The outer body 16 is a metal container in a bottomed cylindrical shape. A gasket 28 is provided between the outer body 16 and the sealing body 17 to ensure the airtightness of the battery case. The outer body 16 has a bulging portion 22 formed by, for example, pressing the side portion from the outside to support the sealing body 17. The bulging portion 22 is preferably formed in an annular shape along the circumference of the outer body 16, and supports the sealing body 17 on its upper surface.

[0025] The sealing body 17 has a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26 and a cover 27 stacked in order from the electrode body 14 side. The components constituting the sealing body 17 have, for example, a disc shape or a ring shape, and the components except the insulating member 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected to each other at their respective central portions, and the insulating member 25 is sandwiched between their respective peripheral portions. If the internal pressure of the battery rises due to abnormal heat, for example, the lower valve body 24 breaks, whereby the upper valve body 26 expands toward the cover 27 side and separates from the lower valve body 24, thereby cutting off the electrical connection between the two. If the internal pressure rises further, the upper valve body 26 breaks, and the gas is discharged from the opening of the cover 27.

[0026] Below, refer to Figure 2 The electrode body 14 will be described. Figure 2 yes Figure 1 The electrode body 14 of the non-aqueous electrolyte secondary battery 10 shown in FIG. 1 is a three-dimensional view of a wound electrode body 14. The electrode body 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the first separator 13a and the second separator 13b interposed therebetween. The positive electrode 11, the negative electrode 12, the first separator 13a and the second separator 13b are all formed into a strip shape, and are wound into a spiral shape around the winding center (hereinafter sometimes referred to as the winding axis) of the electrode body 14, so as to be alternately stacked in the radial direction β of the electrode body 14. Hereinafter, the first separator 13a and the second separator 13b are sometimes collectively referred to as separators 13. In the electrode body 14, the length direction of the positive electrode 11 and the negative electrode 12 becomes the winding direction γ, and the width direction of the positive electrode 11 and the negative electrode 12 becomes the winding axis direction α. ​​It should be noted that, hereinafter, the length direction of the positive electrode 11 and the negative electrode 12 is sometimes referred to as the length direction γ. The inner side of the roll refers to the winding axis side in the radial direction β, and the outer side of the roll refers to the outer side of the electrode body 14 in the radial direction β.

[0027] like Figure 2 As shown, the first separator 13a is arranged on the outside of the roll of the positive electrode 11, and the second separator 13b is arranged on the outside of the roll of the negative electrode 12 (the inside of the roll of the positive electrode 11). The first separator 13a and the second separator 13b are between the positive electrode 11 and the negative electrode 12, thereby insulating the positive electrode 11 and the negative electrode 12 from each other. In addition, the separator 13 protects the positive electrode 11 and the negative electrode 12 from external impact. The separator 13 can be composed of two sheets or one sheet. The first separator 13a and the second separator 13b can be the same as each other or different.

[0028] Next, use Figure 3 The positive electrode 11 will be described in detail. Figure 3 It is a longitudinal cross-sectional view of the positive electrode 11 in one example of the embodiment.

[0029] The positive electrode 11 has a strip-shaped positive electrode collector 30 and a positive electrode mixture layer 31 formed on at least one surface of the positive electrode collector 30. In other words, the positive electrode 11 has a positive electrode mixture layer 31 containing a positive electrode active material on at least one surface. The positive electrode mixture layer 31 is preferably formed on both sides of the positive electrode collector 30. The positive electrode collector 30 is, for example, a foil of a metal such as aluminum, a film having the metal disposed on the surface, or the like. A preferred positive electrode collector 30 is a foil of a metal having aluminum or an aluminum alloy as a main component. The thickness of the positive electrode collector 30 is, for example, 10 μm to 30 μm.

[0030] The positive electrode mixture layer 31 preferably includes a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 is prepared, for example, by applying a positive electrode slurry including a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both sides of the positive electrode collector 30, followed by drying and rolling.

[0031] Examples of the positive electrode active material include lithium-containing composite oxides containing transition metal elements such as Co, Mn, and Ni. The lithium-containing composite oxide is not particularly limited, but is preferably a composite oxide of the general formula Li 1+x A composite oxide represented by MO2 (wherein -0.2<x≤0.2, M contains at least one of Ni, Co, Mn and Al).

[0032] As the example of conductive agent, carbon materials such as carbon black (CB), acetylene black (AB), ketjen black, graphite, etc. can be enumerated. As the example of binding agent, fluorine resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resin, polyolefin resin, etc. can be enumerated. In addition, these resins can also be used in combination with carboxymethyl cellulose (CMC) or its salt, polyethylene oxide (PEO), etc. They can be used alone or in combination with more than two kinds.

[0033] The positive electrode 11 is provided with a positive electrode exposed portion 32 where the surface of the positive electrode current collector 30 is exposed without forming the positive electrode mixture layer 31. There may be one or more positive electrode exposed portions 32. The positive electrode lead 20 is connected to at least one positive electrode exposed portion 32. There may be one or more positive electrode leads 20. Figure 4 1 is a top view showing the opposing relationship between the positive electrode 11 and the first separator 13a in the electrode body 14. Figure 4 As shown, the positive electrode lead 20 is opposite to the first separator 13a provided on the outside of the roll of the positive electrode 11. That is, the positive electrode lead 20 is connected to the positive electrode exposed portion 32 on the outside of the roll of the positive electrode 11. Preferably, the positive electrode exposed portion 32 is also provided on the inside of the roll of the positive electrode 11 at a position corresponding to the positive electrode exposed portion 32 to which the positive electrode lead 20 is connected. The positive electrode lead 20 can be connected to any positive electrode exposed portion 32 on the outside and inside of the roll of the positive electrode 11. The positive electrode lead 20 is joined to the positive electrode exposed portion 32 by, for example, ultrasonic welding. The constituent material of the positive electrode lead 20 is not particularly limited as long as it has conductivity, and is preferably composed of a metal having aluminum as a main component.

[0034] For example, from the viewpoint of current collection, the positive electrode lead 20 may be provided at the center of the length direction γ of the positive electrode 11. In this case, the positive electrode lead 20 is connected to the positive electrode exposed portion 32 provided at the center of the length direction γ of the positive electrode 11, and when the positive electrode 11 is wound into the electrode body 14, as shown in FIG. Figure 2As shown, the positive electrode lead 20 is arranged to protrude from the end surface in the winding axis direction α at the middle position in the radial direction β of the electrode body 14. In addition, the positive electrode exposure portion 32 may be formed other than the central portion in the longitudinal direction γ of the positive electrode 11, for example, it may be formed at a position close to the end. The positive electrode exposure portion 32 is provided, for example, by intermittent coating without coating a part of the positive electrode current collector 30 with the positive electrode slurry.

[0035] like Figure 3 As shown, a protective member 35 is attached to the surface of the positive electrode lead 20. The protective member 35 is an insulating member for the purpose of preventing the positive electrode lead 20 and the positive electrode exposed portion 32 around the positive electrode lead 20 from short-circuiting with the negative electrode mixture layer provided on the surface of the negative electrode 12 described later when the separator 13 is broken and the positive electrode lead 20 and the positive electrode exposed portion 32 around the positive electrode lead 20 are opposed to each other without the separator 13. The protective member 35 is preferably attached to the surface of the positive electrode mixture layer 31 so as to straddle the positive electrode lead 20 and the positive electrode exposed portion 32 around the positive electrode lead 20.

[0036] The protective member 35 includes, for example, a base material and an adhesive portion formed on one surface of the base material. The base material may be made of any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyetheretherketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), etc. The thickness of the base material is, for example, not less than 5 μm and not more than 50 μm, preferably not less than 10 μm and not more than 30 μm.

[0037] The adhesive portion is a portion for bonding the protective member 35 to the surface of the positive electrode 11. The thickness of the adhesive portion is, for example, 1 μm or more and 30 μm or less, preferably 5 μm or more and 25 μm or less. The adhesive portion may include at least one of a rubber polymer and an acrylic polymer. The rubber polymer and the acrylic polymer have adhesive properties, so the protective member 35 can be bonded to the surface of the positive electrode 11. For example, a silicone polymer may be further added to the adhesive portion.

[0038] like Figure 3As shown, the positive electrode 11 has a corner. When the battery is impacted, the separator 13 may be damaged starting from the portion opposite to the corner. Specifically, the corners can be exemplified by the inner end and outer end of the positive electrode 11 (hereinafter, sometimes referred to as corner A), the inner end and outer end of the positive electrode mixture layer 31 (hereinafter, sometimes referred to as corner B), both ends of the width direction of the protective member 35 (hereinafter, sometimes referred to as corner C), and both ends of the width direction of the positive lead 20 (hereinafter, sometimes referred to as corner D). Here, the inner end and the outer end refer to the end of the winding start side and the end of the winding end side of the positive electrode 11 and the negative electrode 12, respectively. In the case where the positive electrode exposed portion 32 adjacent to the inner end and the outer end of the positive electrode 11 are not formed, the inner end and the outer end of the positive electrode mixture layer 31 are respectively consistent with the inner end and the outer end of the positive electrode 11. In addition to the corners A to D, as long as the step difference is generated on the surface of the positive electrode 11, it can also be regarded as a corner.

[0039] The spacer 13 can use a porous sheet with ion permeability and insulation. Specific examples of porous sheets include microporous films, woven fabrics, non-woven fabrics, etc. As the material of the spacer 13, polyolefin resins such as polyethylene and polypropylene can be used. The thickness of the spacer 13 is, for example, 8μm to 50μm, preferably 10μm to 20μm. The spacer 13 has a melting point of, for example, about 130°C to 180°C. In addition, in order to improve heat resistance, etc., the spacer 13 can also form an aromatic polyamide coating on the surface.

[0040] The spacer 13 is produced by extruding a polyolefin resin into a sheet shape, and then stretching it in a flow direction (MD: Machine Direction) and a direction perpendicular to the flow direction (TD: Transverse Direction) simultaneously or sequentially to form a film. The produced spacer 13 is wound up to form a spacer roll 54 (see Figure 5 ). The spacer 13 is stretched to orient the molecules of the polyolefin resin, and the puncture strength can be improved by crystallization. On the other hand, the amount of stretching of the polyolefin resin is predetermined, and if the polyolefin resin is stretched during film formation, the elongation of the spacer 13 after film formation becomes smaller. That is, the elongation of the spacer 13 and the puncture strength become a trade-off relationship.

[0041] like Figure 4As shown, the first spacer 13a has a normal portion 40 and a plastic deformation portion 41 having a higher puncture strength than the normal portion 40. When the battery is fully charged and when it is not fully charged, the behavior of the battery internal short circuit when it is impacted from the outside is different. In the fully charged state, the electrode body 14 expands to the maximum, so the gap between the electrode body 14 and the outer body 16 becomes smaller, and the amount of deformation allowed by the electrode body 14 when the battery is impacted from the outside becomes smaller. In this case, the spacer 13a is Figure 3 The corners shown in the figure are locally compressed and broken, which easily causes internal short circuit. Figure 4 As shown, it is preferred to provide a plastic deformation portion 41 at a position where the spacer 13 is locally compressed when the battery is expected to be impacted from the outside. Thus, the internal short circuit of the battery in a fully charged state when it is impacted from the outside is suppressed. On the other hand, in a non-fully charged state, the electrode body 14 shrinks compared to the fully charged state, so the gap between the electrode body 14 and the outer body 16 becomes larger, and the amount of deformation allowed by the electrode body 14 when the battery is impacted from the outside becomes larger. In this case, there is a possibility that the spacer 13 breaks due to the tensile force as the electrode body 14 is deformed, thereby generating an internal short circuit. As described above, the elongation of the spacer 13 is in a compromise relationship with the puncture strength, so the elongation of the normal portion 40 becomes higher than that of the plastic deformation portion 41, and the breakage of the spacer 13 corresponding to the tensile force is suppressed. Thus, the internal short circuit of the battery in a non-fully charged state when it is impacted from the outside is suppressed. Therefore, since the separator 13 includes the normal portion 40 and the plastic deformation portion 41 , internal short circuit of the battery due to external impact is suppressed in both the fully charged state and the non-fully charged state.

[0042] The puncture strength is measured in accordance with JIS standard JIS Z-1707. A semicircular needle with a diameter of 1.0 mm and a tip diameter of 0.5 mm is inserted into a fixed puncture strength measurement sample (spacer 13) at a speed of 50±5 mm / min, and the maximum stress until the needle penetrates is measured. Five puncture strength measurement samples randomly selected are measured, and the average value of the measurement results is taken as the puncture strength value of the spacer 13.

[0043] The elongation in the winding axis direction α is measured in accordance with JIS standard JIS K-7127. The first spacer 13a and the second spacer 13b are cut into 10 mm in width and 150 mm in length, respectively, to prepare 5 elongation measurement specimens. The elongation measurement specimens are installed on the shaft of the testing machine in a manner that the length direction is consistent and the distance between a pair of clamps is 100 mm. The tensile force and elongation when the elongation measurement specimen is stretched at 200 mm / min are measured to measure the elongation in the winding axis direction α. ​​In addition, the tensile force at break (hereinafter sometimes referred to as the breaking strength) is also measured. Five elongation measurement specimens are measured, and each measurement result adopts the average value of the three after removing the largest and smallest ones.

[0044] The first separator 13a may have a plastic deformation portion 41A at a position opposite to at least one of the corners A at the inner end and the outer end of the positive electrode 11. The corner A may locally compress and puncture the first separator 13a when the battery is subjected to an impact from the outside. Therefore, by configuring a plastic deformation portion 41A having a higher puncture strength than the normal portion 40 at a position opposite to the corner A, the first separator 13a is not easily damaged, and the risk of internal short circuit can be reduced. In the second separator 13b, a plastic deformation portion 41A may also be provided at a position opposite to at least one of the corners A at the inner end and the outer end of the positive electrode 11.

[0045] The first separator 13a may have a plastic deformation portion 41B at a position opposite to at least one of the corners B at the inner and outer ends of the positive electrode mixture layer 31. The positive electrode mixture layer 31 contains a hard lithium-containing composite oxide as a positive electrode active material. Therefore, when the battery is subjected to an impact from the outside, the corner B may puncture the first separator 13a. Therefore, by configuring a plastic deformation portion 41B having a higher puncture strength than the normal portion 40 at a position opposite to the corner B, the first separator 13a becomes less prone to damage, which can reduce the risk of internal short circuit. In the case where the positive electrode mixture layer 31 is formed on both surfaces of the positive electrode 11, in the second separator 13b, a plastic deformation portion 41B may also be provided at a position opposite to at least one of the corners B at the inner and outer ends of the positive electrode mixture layer 31.

[0046] The plastic deformation portion 41A and the plastic deformation portion 41B are provided at relatively close positions in the longitudinal direction γ of the positive electrode 11, so the plastic deformation portion 41A and the plastic deformation portion 41B can be connected to form one plastic deformation portion 41. In this case, the man-hours for plastic deformation can be reduced, so the method for forming the plastic deformation portion 41 described later becomes simpler.

[0047] The first separator 13a may have a plastic deformation portion 41C at a position opposite to at least one of the corners C at both ends of the width direction of the protective member 35. The corner C may also pierce the first separator 13a when the battery is subjected to an impact from the outside. Therefore, by configuring a plastic deformation portion 41C having a higher puncture strength than the normal portion 40 at a position opposite to the corner C, the first separator 13a is not easily damaged, and the risk of internal short circuit can be reduced. In addition, the position where the protective member 35 is attached to the surface of the positive electrode 11 is not limited to the surface of the positive lead 20, and can also be attached to other positions. In this case, the plastic deformation portion 41C can also be configured at a position opposite to at least one of the corners C at both ends of the width direction of the protective member 35. In the case where the protective member 35 is attached to the inner side of the roll of the positive electrode 11, in the second separator 13b, a plastic deformation portion 41C can also be provided at a position opposite to at least one of the corners C at both ends of the width direction of the protective member 35.

[0048] The first separator 13a may have a plastic deformation portion 41D at a location facing at least one of the corner portions D at both ends in the width direction of the positive electrode lead 20. Figure 3 As shown in FIG. 1 , the positive electrode lead 20 is thicker than the positive electrode mixture layer 31, and therefore is the part that protrudes most toward the first separator 13a on the surface of the positive electrode 11. In addition, the positive electrode lead 20 is not easily bent when the positive electrode 11 is wound. Therefore, when the battery is impacted from the outside, a particularly strong force is applied to the part of the first separator 13a that is opposite to the two ends in the width direction of the positive electrode lead 20. Therefore, as shown in FIG. Figure 4 As shown, by forming the plastic deformation portion 41D at the portion of the first separator 13a opposite to the corner portion D, the first separator 13a is not easily damaged, and the risk of internal short circuit can be reduced. In the case where the positive electrode lead 20 is provided inside the roll of the positive electrode 11, the second separator 13b may also be provided with a plastic deformation portion 41D at a portion opposite to at least one of the corner portions D at both ends in the width direction of the positive electrode lead 20.

[0049] The plastic deformation portion 41C and the plastic deformation portion 41D are provided at relatively close positions in the longitudinal direction γ of the positive electrode 11, so the plastic deformation portion 41C and the plastic deformation portion 41D can be connected to form one plastic deformation portion 41. In this case, the man-hours for plastic deformation can be reduced, so the method for forming the plastic deformation portion 41C and the plastic deformation portion 41D described later becomes simpler.

[0050] Figure 4 The first spacer 13a has the plastic deformation parts 41A, 41B, 41C, and 41D, but may have only one of the plastic deformation parts 41A, 41B, 41C, and 41D, or may selectively have a plurality of them. Figure 3When the portion locally pressed by the positive electrode 11 other than the portions where the corners A, B, C, and D face each other is assumed to be the first separator 13a, the plastic deformation portion 41 may be provided at the portion. The same applies to the second separator 13b.

[0051] Next, use Figure 5 and Figure 6 An example of a method for forming the plastic deformation portion 41 will be described. Figure 5 It is a front view showing the structure of a winding device for the electrode body 14 as an example of the embodiment.

[0052] exist Figure 5 In the embodiment, the positive electrode 11, the first separator 13a, the negative electrode 12, and the second separator 13b are rolled up from the inner side of the roll to form the electrode body 14. The first separator 13a is unwound from the separator roll 54 and is wound together with the positive electrode 11, the negative electrode 12, and the second separator 13b while adjusting the tension by the dancer roller 52.

[0053] The plastic deformation portion 41 is formed in the following manner: when the first separator 13a is wound, a part of the first separator 13a is stretched and plastically deformed by the stretching portion 50a and the stretching portion 50b along the winding direction γ. The first separator 13a has ductility, but if it is stretched with a force exceeding the yield point, it will not recover and produce plastic deformation. The plastic deformation portion 41 that has produced plastic deformation has a higher puncture strength than the normal portion 40 that has not been plastically deformed. On the other hand, the normal portion 40 has a higher elongation than the plastic deformation portion 41. The plastic deformation portion 41 is different from thermal welding, and will not block the hole of the separator 13, so the permeability of the electrolyte is good.

[0054] Figure 6 Yes means Figure 5 The side view of the structure of the stretching part 50a and the stretching part 50b of the winding device shown. The first spacer 13a is from Figure 6The direction from the upper side to the lower side, in other words, from the separator roll 54 side to the electrode body 14 side (hereinafter sometimes referred to as the flow direction F of the first separator 13a). As long as the first separator 13a between the stretching section 50a and the stretching section 50b can be stretched, the structure of the stretching section 50a and the stretching section 50b is not particularly limited. The stretching section 50a and the stretching section 50b can be set as clamping rollers, for example. The stretching section 50a and the stretching section 50b clamp the first separator 13a from a direction perpendicular to the flow direction F of the first separator 13a, respectively. By rotating the clamping roller of the stretching section 50b along the flow direction F of the first separator 13a faster than the clamping roller of the stretching section 50a, the first separator 13a between the stretching section 50a and the stretching section 50b can be stretched. By adjusting the distance between the stretching section 50a and the stretching section 50b, the length of the winding direction γ of the plastic deformation section 41 can be changed. Therefore, the plastic deformation portion 41 can be formed at any position of the first spacer 13a. The same method can be used when the plastic deformation portion 41 is formed at a specific position of the second spacer 13b.

[0055] Next, use Figure 7 Another example of implementation is described. Figure 7 In the example shown, the first separator 13a is stretched and plastically deformed between the stretching section 50a and the electrode body 14 being produced, thereby forming the plastic deformation section 41. For example, the first separator 13a can be stretched by making the rotation speed of the nip roller of the stretching section 50a slower than the winding speed of the electrode body 14.

[0056] The negative electrode 12 in this embodiment is as follows, for example.

[0057] The negative electrode 12 has a strip-shaped negative electrode current collector and a negative electrode mixture layer formed on at least one surface of the negative electrode current collector. The negative electrode mixture layer is preferably formed on both sides of the negative electrode current collector. The negative electrode current collector can be, for example, a foil of a metal such as copper, or a film having the metal disposed on the surface. A preferred negative electrode current collector is a foil of a metal having copper or a copper alloy as a main component. The thickness of the negative electrode current collector is, for example, 5 μm to 30 μm.

[0058] The negative electrode mixture layer is preferably formed on both sides of the negative electrode collector in the entire area except for the negative electrode exposed portion described later. The negative electrode mixture layer preferably includes a negative electrode active material and a binder. The negative electrode 12 is prepared, for example, by applying a negative electrode slurry including a negative electrode active material, a binder, and water to both sides of the negative electrode collector, followed by drying and rolling.

[0059] As the negative electrode active material, there is no particular limitation as long as it can reversibly absorb and release lithium ions. For example, carbon materials such as natural graphite and artificial graphite, metals such as Si and Sn alloyed with lithium, or alloys and oxides containing them can be used. The binder contained in the negative electrode mixture layer can use fluorine resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resin, polyolefin resin, etc. In the case of preparing the negative electrode slurry with an aqueous solvent, styrene-butadiene rubber (SBR), CMC or its salt, polyacrylic acid or its salt, polyvinyl alcohol, etc. can be used. They can be used alone or in combination of two or more.

[0060] The negative electrode 12 is provided with a negative electrode exposed portion where the surface of the negative electrode current collector is exposed. The negative electrode exposed portion is a portion to which the negative electrode lead 21 is connected, and is a portion of the surface of the negative electrode current collector that is not covered by the negative electrode mixture layer. The negative electrode lead 21 is joined to the negative electrode exposed portion by, for example, ultrasonic welding. The constituent material of the negative electrode lead 21 is not particularly limited as long as it has conductivity. The negative electrode lead 21 is preferably composed of a metal having nickel or copper as a main component, or a metal containing both nickel and copper.

[0061] The negative electrode exposed portion is provided, for example, at the inner end portion in the longitudinal direction γ of the negative electrode 12. In this case, Figure 2 As shown, the negative electrode lead 21 is arranged at the center of the radial direction β of the electrode body 14 so as to protrude from the end surface in the winding axis direction α. ​​A protective member 35 may be attached to the surface of the negative electrode lead 21. The negative electrode exposed portion is provided, for example, by intermittent coating without coating a portion of the negative electrode current collector with the negative electrode slurry. The arrangement position of the negative electrode lead 21 is not limited to Figure 2 In the example shown, a negative electrode lead 21 may be provided at the outer end of the negative electrode 12. In addition, a negative electrode lead 21 may be provided at both the inner end and the outer end. In this case, the current collection property is improved. By making the exposed portion of the outer end of the negative electrode 12 contact the inner peripheral surface of the outer casing 16, the outer end of the negative electrode 12 can be electrically connected to the outer casing 16 without using the negative electrode lead 21.

[0062] A plastic deformation portion 41 can be formed at a portion of the first separator 13a or the second separator 13b that is opposite to a corner in the negative electrode 12, such as the inner end or outer end of the negative electrode 12 (equivalent to corner A), the end of the negative electrode mixture layer (equivalent to corner B), the width direction end of the protective member 35 (equivalent to corner C), or the width direction end of the negative electrode lead 21 (equivalent to corner D).

[0063] Example

[0064] Hereinafter, the present invention will be further described by way of examples, but the present invention is not limited to these examples.

[0065] <Example>

[0066] [Production of positive electrode]

[0067] As the positive electrode active material, LiNi 0.88 Co 0.09 Al 0.03 100 parts by mass of LiNi 0.88 Co 0.09 Al 0.03 O2, 1.0 parts by mass of acetylene black and 0.9 parts by mass of polyvinylidene fluoride (PVDF) were mixed, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a positive electrode slurry. Next, the positive electrode slurry was applied to both sides of a long strip of positive electrode collector formed by an aluminum foil with a thickness of 15 μm, and the coating was heated to 100°C to 150°C to dry it. After the dried coating was compressed with a roller to a thickness of 0.144 mm, it was cut into a width of 57.6 mm and a length of 679 mm to make a positive electrode with a positive electrode mixture layer formed on both sides of the positive electrode collector.

[0068] [Production of negative electrode]

[0069] 95 parts by mass of graphite powder, 5 parts by mass of Si oxide, 1 part by mass of carboxymethyl cellulose (CMC) and 1 part by mass of styrene-butadiene rubber were mixed, and an appropriate amount of water was added to prepare a negative electrode slurry. Next, the negative electrode slurry was applied to both sides of a long strip of negative electrode collector formed by a copper foil with a thickness of 8 μm, and the coating was dried. The dried coating was compressed using a roller to a thickness of 0.164 mm, and then cut into a width of 58.6 mm and a length of 662 mm to make a negative electrode with a negative electrode mixture layer formed on both sides of the negative electrode collector.

[0070] [Spacer]

[0071] The first and second spacers used the same spacer. The spacer used was made of a polyolefin resin with a thickness of 14 μm and an aromatic polyamide coating was formed on one surface. The physical properties of the spacer used were that the breaking strength of the normal part was 135 MPa, the elongation in the winding axis direction α was 78%, and the puncture strength was 413 gf.

[0072] [Preparation of electrolyte]

[0073] 3 parts by mass of vinylene carbonate (VC) were added to 100 parts by mass of a mixed solvent consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (EC:EMC:DMC=20:5:75 by volume ratio). LiPF6 was dissolved in the mixed solvent to a concentration of 1.4 mol / L to prepare an electrolyte.

[0074] [Impact test]

[0075] An aluminum positive lead is installed on the exposed portion of the positive electrode disposed approximately in the center of the length direction of the positive electrode collector. A protective member having a substrate portion made of PP is attached to the surface of the positive electrode lead in a manner overlapping with the positive electrode mixture layer. A nickel-copper-nickel negative lead is installed on the exposed portion of the negative electrode disposed at the inner end of the negative electrode collector. Ten wound electrode bodies are made by overlapping and winding in the order of the positive electrode, the first separator, the negative electrode, and the second separator from the inside of the roll. When winding the electrode body, for both the first separator and the second separator, a pair of clamping rollers are arranged between the separator roll and the electrode body, and the clamping rollers are clamped and stretched in a manner that a load of 12N is applied to a width of 10mm to form a plastic deformation portion. The plastic deformation portion is formed at the position covering the positive electrode tab protection band. In addition, the puncture strength of the plastic deformation portion formed by plastically deforming the separator under the same conditions is 436gf. Then, insulating plates were arranged on the upper and lower parts of the electrode body, and the electrode body was housed in the battery case. Next, the negative electrode lead was welded to the bottom of the battery case, and the positive electrode lead was welded to the sealing body of the safety valve with internal pressure operation. Then, after injecting electrolyte into the interior of the battery case by decompression, the open end of the battery case was sealed by riveting the open end of the battery case to the sealing body through a sealing gasket, and 10 cylindrical secondary batteries were produced.

[0076] For the case of SOC 100%, a collision test was performed using the 5 batteries produced. After any battery was charged to 4.2V at a constant current of 990mA (0.3 hour rate) in an atmosphere of 25°C, a constant voltage charge with a termination current of 66mA was performed at 4.2V. Then, the weight of the weight in the T6 collision test item of the UN transport test condition (a metal round bar with a diameter of 15.8mm is placed in the center of the battery, and a weight of 9.1kg is dropped from a height of 61cm) was changed to 9.6kg for the test. The case where the voltage of all 5 batteries did not drop by more than 0.5V compared to before the test was set as OK, and the other cases were set as NG.

[0077] For the case of SOC50%, a collision test was carried out using the five batteries produced. Each battery was charged at a constant current of 990mA (0.3 hour rate) in an atmosphere of 25°C, and the charging was terminated when the charging capacity reached 1.7Ah. Then, the weight of the weight in the T6 collision test item of the UN transport test condition (a metal round bar with a diameter of 15.8mm is placed in the center of the battery, and a weight of 9.1kg is dropped from a height of 61cm) was changed to 9.6kg for the test. The case where the voltage of all five batteries did not drop by more than 0.5V compared to before the test was recorded as OK, and the rest was recorded as NG.

[0078] <Comparative Example 1>

[0079] The first and second separators were made of separators with higher puncture strength than the separators of Example 1, and no plastic deformation portion was formed in the first and second separators. A wound electrode body was produced in the same manner as in Example 1. The physical properties of the separators used were as follows: the breaking strength of the normal portion was 145 MPa, the elongation in the winding axis direction α was 50%, and the puncture strength was 456 gf.

[0080] <Comparative Example 2>

[0081] A wound electrode body was produced in the same manner as in Example 1 except that the plastic deformation portion was not formed in the first separator and the second separator.

[0082] Table 1 shows the evaluation results of Examples and Comparative Examples.

[0083] [Table 1]

[0084]

[0085] In Example 1, in which a plastic deformation portion is formed in both the first separator and the second separator, the impact test is OK in both the full charge state (SOC100%) and the non-full charge state (SOC50%). On the other hand, in Comparative Examples 1 and 2, in which the separator does not form a plastic deformation portion, the impact test is NG in either the full charge state or the non-full charge state. Comparative Example 1, which uses a separator with high puncture strength, is NG in the impact test in the non-full charge state, and Comparative Example 2, which uses a separator with low puncture strength, is NG in the impact test in the full charge state. In this way, it is confirmed that by using a separator having a normal portion and a plastic deformation portion having a higher puncture strength than the normal portion, a non-aqueous electrolyte secondary battery can be obtained that can suppress thermal runaway of the battery caused by external impact in either the full charge state or the non-full charge state.

[0086] Description of Reference Numerals

[0087] 10: non-aqueous electrolyte secondary battery, 11: positive electrode, 12: negative electrode, 13: separator, 14: electrode body, 15: battery case, 16: outer body, 17: sealing body, 18, 19: insulating plate, 20: positive electrode lead, 21: negative electrode lead, 22: bulging part, 23: filter, 24: lower valve body, 25: insulating member, 26: upper valve body, 27: cover, 28: sealing gasket, 30: positive electrode collector, 31: positive electrode mixture layer, 35: protective member, 40 normal part, 41, 41A, 41B, 41C, 41D: plastic deformation part, 50a, 50b: stretching part, 52: tension adjustment roller, 54: separator roll

Claims

1. A non-aqueous electrolyte secondary battery comprising: A wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; and a battery case, the battery case housing the electrode body, The positive electrode comprises a positive electrode current collector and a positive electrode mixture layer formed on at least one surface of the positive electrode current collector. The spacer has a normal portion and a plastic deformation portion having a higher puncture strength than the normal portion, The plastic deformation portion is formed by stretching a portion of the spacer along the winding direction.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein The separator has the plastic deformation portion at a location facing at least one of an inner end portion and an outer end portion of the positive electrode.

3. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein: The separator has the plastic deformation portion at a location facing at least one of an inner end portion and an outer end portion of the positive electrode mixture layer.

4. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein: Also available: a conductive positive electrode lead connected to a positive electrode exposed portion of a surface of the positive electrode where the positive electrode mixture layer is not formed; and a protective member attached to the surface of the positive electrode lead, The separator has the plastic deformation portion at a location facing at least one of both ends in the width direction of the protection member and both ends in the width direction of the positive electrode lead.

5. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein: The separator includes a polyolefin-based resin.

6. A method for manufacturing a non-aqueous electrolyte secondary battery, wherein: The nonaqueous electrolyte secondary battery comprises a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and a battery case for housing the electrode body. When the positive electrode and the negative electrode are wound with the separator interposed therebetween, a portion of the separator is stretched in a winding direction to plastically deform the portion to form a plastically deformed portion having a higher puncture strength than a normal portion that is not plastically deformed.

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