Non-aqueous electrolyte secondary battery

Abstract

The object of the present invention is to provide a non-aqueous electrolyte secondary battery, which can improve the insulation between the positive electrode and the negative electrode and can suppress the thermal runaway of the battery caused by external impact in the charging 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 the positive electrode and the negative electrode are wound with a first separator and a second separator, the first separator is arranged on the outside of the positive electrode roll, and the second separator is arranged on the inside of the positive electrode roll, and the puncture strength of the second separator is higher than the puncture strength of the first separator.

Description

Technical Field

[0001] The present invention relates to a 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 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, in non-aqueous electrolyte secondary batteries, ensuring the electrical insulation between the positive electrode and the negative electrode is an important issue. The insulation between the positive electrode and the negative electrode is evaluated by, for example, applying a high voltage to the electrode body before being impregnated with the electrolyte, and measuring the withstand voltage test of the leakage current flowing between the positive electrode and the negative electrode. The withstand voltage test is carried out in order to discharge defective products with insufficient insulation between the positive electrode and the negative electrode in the manufacturing process of the non-aqueous electrolyte secondary battery. Therefore, ensuring the insulation between the positive electrode and the negative electrode is related to the reduction of the defective rate in the manufacturing process. The technology disclosed in Patent Document 1 does not take into account such insulation between the positive electrode and the negative electrode, and there is still room for improvement.

[0008] An object of the present invention is to provide a nonaqueous electrolyte secondary battery capable of improving the insulation between a positive electrode and a negative electrode and suppressing thermal runaway of the battery caused by an external impact in a 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 has a wound electrode body in which a positive electrode and a negative electrode are wound with a first separator and a second separator therebetween, the first separator being arranged on the outside of the roll of the positive electrode, the second separator being arranged on the inside of the roll of the positive electrode, and the puncture strength of the second separator being higher than the puncture strength of the first separator.

[0011] Effects of the Invention

[0012] According to the nonaqueous electrolyte secondary battery of the present invention, the insulation between the positive electrode and the negative electrode can be improved, and thermal runaway of the battery caused by external impact in a charged state can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery as an example of an embodiment.

[0014] Figure 2 yes Figure 1 A perspective view of a wound electrode body of a nonaqueous electrolyte secondary battery shown. DETAILED DESCRIPTION

[0015] 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 illustration 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 assumed at the beginning of the application that their characteristic parts are appropriately combined and used.

[0016] Figure 1 FIG. 1 is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery 10 as an example of an embodiment. Figure 1 As 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 the 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 the electrolyte salt of the non-aqueous electrolyte, LiPF 6 , LiBF 4 、LiCF 3 SO 3 The amount of the electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 to 2.0 mol / L.

[0017] 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 cap 27 of the top plate of the sealing body 17 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.

[0018] 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.

[0019] The sealing body 17 has a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26 and a cap 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 an 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 cap 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 cap 27.

[0020] Below, refer to Figure 2 The electrode body 14 will be described in detail. Figure 2 yes Figure 13D view of a wound electrode body 14 of a non-aqueous electrolyte secondary battery 10 shown in FIG. The electrode body 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound with a first separator 13a and a 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 in a strip shape, and are wound in a spiral shape around a winding axis that is the winding center of the electrode body 14 to form a state of alternating stacking in the radial direction β of the electrode body 14. 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. In addition, 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.

[0021] The positive electrode 11 has a strip-shaped positive electrode collector and a positive electrode active material layer formed on at least one surface of the positive electrode collector. In other words, the positive electrode 11 has a positive electrode active material layer containing a positive electrode active material on at least one surface. The positive electrode active material layer is preferably formed on both sides of the positive electrode collector. The positive electrode collector can be, 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 is a foil of a metal having aluminum or an aluminum alloy as a main component. The thickness of the positive electrode collector is, for example, 10 μm to 30 μm.

[0022] The positive electrode active material layer is preferably formed on both sides of the positive electrode collector in the entire area except for the positive electrode exposed portion described later. The positive electrode active material layer 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 containing 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, followed by drying and rolling.

[0023] 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 MO 2 (wherein, -0.2<x≤0.2, M contains at least one of Ni, Co, Mn and Al).

[0024] 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.

[0025] The positive electrode 11 is provided with a positive electrode exposed portion where the surface of the positive electrode current collector is exposed. The positive electrode exposed portion is a portion to which the positive electrode lead 20 is connected, and is a portion of the surface of the positive electrode current collector that is not covered by the positive electrode active material layer. The positive electrode lead 20 is joined to the positive electrode exposed portion by, for example, ultrasonic welding. The constituent material of the positive electrode lead 20 is not particularly limited as long as it has conductivity. The positive electrode lead 20 is preferably composed of a metal having aluminum as a main component.

[0026] The positive electrode exposed portion can be provided, for example, at the center of the length direction γ of the positive electrode 11. The positive electrode exposed portion can be formed near the end of the length direction γ of the positive electrode 11, but from the viewpoint of current collection, it is preferably provided at a position substantially equidistant from both ends of the length direction γ. By connecting the positive electrode lead 20 to the positive electrode exposed portion provided at such a position, when winding into the electrode body 14, as shown in FIG. Figure 2 As 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. The positive electrode exposed portion is provided by intermittent coating of the positive electrode slurry without coating a part of the positive electrode current collector, for example.

[0027] The negative electrode 12 has a strip-shaped negative electrode collector and a negative electrode active material layer formed on at least one surface of the negative electrode collector. The negative electrode active material layer is preferably formed on both sides of the negative electrode collector. The negative electrode 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 collector is a foil of a metal having copper or a copper alloy as a main component. The thickness of the negative electrode collector is, for example, 5 μm to 30 μm.

[0028] The negative electrode active material 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 active material 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.

[0029] 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 active material layer can use fluorine resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resin, polyolefin resin, etc. in the same way as in the case of positive electrode 11. 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.

[0030] 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 positive electrode active material layer. The negative electrode lead 21 is joined to the positive 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.

[0031] 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. ​​Here, the inner end and the outer end refer to the end of the inner side of the roll of the positive electrode 11 and the end of the outer side of the roll of the negative electrode 12. The negative electrode exposed portion is provided, for example, by intermittent coating of the negative electrode slurry without coating a part of the negative electrode current collector. 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 terminal end of the negative electrode 12 contact the inner peripheral surface of the battery case 15, the terminal end of the negative electrode 12 can be electrically connected to the battery case 15 without using the negative electrode lead 21.

[0032] like Figure 2 As shown, the first separator 13a is disposed on the outside of the roll of the positive electrode 11, and the second separator 13b is disposed on the inside of the roll of the positive electrode 11. The first separator 13a and the second separator 13b are interposed between the positive electrode 11 and the negative electrode 12, thereby physically and electrically separating the positive electrode 11 and the negative electrode 12. In addition, the first separator 13a and the second separator 13b protect the positive electrode 11 and the negative electrode 12 when they are impacted from the outside.

[0033] The first spacer 13a and the second spacer 13b 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 base material of the first spacer 13a and the second spacer 13b, polyolefin resins such as polyethylene and polypropylene can be used. The thickness of the first spacer 13a and the second spacer 13b is, for example, 10μm to 50μm, preferably 9μm to 17μm. The first spacer 13a and the second spacer 13b have a melting point of about 130°C to 180°C, for example.

[0034] The puncture strength of the second separator 13b is higher than the puncture strength of the first separator 13a. Thus, the insulation between the positive electrode 11 and the negative electrode 12 can be improved. The reason is considered to be as follows. If the positive electrode 11 and the negative electrode 12 are wound into a spiral shape, the active material layer on the inner side of each roll is subjected to compressive stress. Since the positive electrode 11 contains a hard active material, there is a situation where the positive electrode active material layer cannot absorb the compressive stress. Therefore, the second separator 13b on the inner side of the roll of the positive electrode 11 is more susceptible to stress from the positive electrode mixture layer than the first separator 13a on the outer side of the roll. Therefore, increasing the puncture strength of the second separator 13b is an effective means for improving the insulation between the positive electrode 11 and the negative electrode 12. 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 front end diameter of 0.5 mm is pierced through a fixed puncture strength measurement sample (spacer) at a speed of 50±5 mm / min, and the maximum stress until the needle penetrates is measured. Five randomly selected puncture strength measurement samples were measured, and the average value of the measurement results was taken as the puncture strength value of the separator.

[0035] In addition, by arranging the first separator 13a on the outside of the roll of the positive electrode 11 and arranging the second separator 13b on the inside of the roll of the positive electrode 11, the rupture of the separator when the non-aqueous electrolyte secondary battery 10 is impacted from the outside is suppressed. Therefore, even if an impact from the outside is applied to the non-aqueous electrolyte secondary battery 10 in a charged state, thermal runaway can be suppressed. The first separator 13a with low puncture strength tends to have a high elongation in the winding axis direction α compared with the second separator 13b. Therefore, it is speculated that the difference in elongation between the first separator 13a and the second separator 13b helps to suppress thermal runaway. Therefore, by configuring the first separator 13a with low puncture strength on the outside of the roll of the positive electrode 11 and configuring the second separator 13b with high puncture strength on the inside of the roll of the positive electrode 11, the insulation between the positive electrode 11 and the negative electrode 12 is improved, and a non-aqueous electrolyte secondary battery 10 that can effectively withstand impacts from the outside can be obtained.

[0036] The first separator 13a preferably has a puncture strength of 3.0N or more and less than 3.9N, and an elongation in the winding axis direction α of 185% or more and 260% or less, and more preferably has a puncture strength of 3.0N or more and 3.7N or less, and an elongation in the winding axis direction α of 185% or more and 220% or less. The second separator 13b preferably has a puncture strength of 3.9N or more and 6.0N or less, and an elongation in the winding axis direction α of 170% or more and 240% or less, and more preferably has a puncture strength of 3.9N or more and 5.0N or less, and an elongation in the winding axis direction α of 170% or more and 200% or less.

[0037] 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 pieces with a width of 10 mm to 25 mm and a length of 150 mm or more to prepare elongation measurement samples. The elongation measurement sample is mounted on a fixture in such a manner that the length direction thereof coincides with the axis of the testing machine, and the tensile force and elongation when the elongation measurement sample is stretched at a constant speed are measured to measure the elongation in the winding axis direction α.

[0038] In addition, when the negative electrode lead 21 is provided at the inner end portion in the longitudinal direction γ of the negative electrode 12, the insulation between the positive electrode 11 and the negative electrode 12 may be reduced at the outer side of the winding of the negative electrode lead 21. Therefore, when the negative electrode lead 21 is provided at the inner end portion in the longitudinal direction γ of the negative electrode 12, the effect of the present embodiment of improving the insulation between the positive electrode 11 and the negative electrode 12 becomes significant.

[0039] The first spacer 13a and the second spacer 13b are made by extruding a polyolefin resin and forming it into a sheet, and then stretching it in the flow direction (MD: Machine Direction) and the direction perpendicular to the flow direction (TD: Transverse Direction) simultaneously or sequentially to make it into a film. By stretching, the molecules of the polyolefin resin are oriented, and the puncture strength can be improved through crystallization. On the other hand, the amount of stretchable polyolefin resin is predetermined. If it is stretched during filming, the elongation of the first spacer 13a and the second spacer 13b after filming becomes smaller. That is, the elongation of the first spacer 13a and the second spacer 13b is in a trade-off relationship with the puncture strength.

[0040] Example

[0041] Hereinafter, the present invention will be further described by way of examples, but the present invention is not limited to these examples.

[0042] <Example>

[0043] [Production of positive electrode]

[0044] As the positive electrode active material, LiNi 0.88 Co 0.09 Al 0.03 O 2 100 parts by mass of LiNi 0.88 Co 0.09 Al 0.03 O 2 , 1.0 parts by mass of acetylene black, 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. The dried coating was compressed with a roller to a thickness of 0.144 mm, and then cut into a width of 62.6 mm and a length of 861 mm to produce a positive electrode with a positive electrode active material layer formed on both sides of the positive electrode collector.

[0045] [Production of negative electrode]

[0046] 95 parts by mass of graphite, 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 consisting of a copper foil with a thickness of 8 μm, and the coating was dried. The dried coating was compressed with a roller to a thickness of 0.160 mm, and then cut into a width of 64.2 mm and a length of 959 mm to produce a negative electrode with a negative electrode active material layer formed on both sides of the negative electrode collector.

[0047] [Spacer]

[0048] Two types of spacers made of polyolefin resin were prepared. As the first spacer, spacer A was used, which had a thickness of 15 μm, a puncture strength of 3.8 N, and an elongation of 247% in the winding axis direction. In addition, as the second spacer, spacer B was used, which had a thickness of 15 μm, a puncture strength of 3.9 N, and an elongation of 178% in the winding axis direction.

[0049] [Preparation of electrolyte]

[0050] 5 parts by mass of vinylene carbonate (VC) was added to 100 parts by mass of a mixed solvent consisting of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC:DMC=1:3 in volume ratio). LiPF was dissolved in the mixed solvent to a concentration of 1.5 mol / L. 6 , prepare the electrolyte.

[0051] [Withstand pressure test]

[0052] Ten electrode bodies in a wound form were wound up in the order of the second separator, the positive electrode, the first separator, and the negative electrode from the inside of the roll. An AC voltage of 1200 V was applied to each electrode body at 45°C to confirm whether a current of 100 mA or more flowed through it. The electrode body with a current of 100 mA or more was considered defective, and the electrode body without the current was considered good, and the defect rate was calculated.

[0053] [Impact test]

[0054] Two wound electrode bodies are made by overlapping and winding in the order of the second separator, the positive electrode, the first separator, and the negative electrode from the inside of the roll. Insulating plates are arranged on the top and bottom of the electrode body, and the electrode body is housed in the battery case. Next, the negative electrode lead is welded to the bottom of the battery case, and the positive electrode lead is welded to the sealing body of the safety valve with an internal pressure working type. Then, after injecting the electrolyte into the interior of the battery case by decompression, the open end of the battery case is sealed by riveting the open end of the battery case to the sealing body through a sealing gasket to make two cylindrical secondary batteries. After the manufactured battery is charged to 3.75V at a constant current charge of 1410mA (0.3 hour rate) in an atmosphere of 25°C, a constant voltage charge with a termination current of 94mA is performed at 3.75V. Then, for one battery, the T6 collision test item of the UN transport test condition (a metal round bar with a diameter of 15.8 mm is placed in the center of the battery, and a 9.1 kg weight is dropped from a height of 61 cm) is tested. For another battery, a 9.1 kg weight is dropped from a height of 80 cm. Otherwise, the test is performed in the same manner as the previous battery. Within 6 hours after the test, check whether there is a fire from each battery and a battery rupture. The case where there is no fire or rupture is set as good, and the case other than this is set as bad.

[0055] <Comparative Example 1>

[0056] A wound electrode body was produced in the same manner as in Example 1 except that the separator A was used as the first separator and the second separator.

[0057] <Comparative Example 2>

[0058] A wound electrode body was produced in the same manner as in Example 1 except that the separator B was used as the first separator and the second separator.

[0059] <Comparative Example 3>

[0060] A wound electrode body was produced in the same manner as in Example 1 except that the separator B was used as the first separator and the separator A was used as the second separator.

[0061] Table 1 shows the evaluation results of Examples and Comparative Examples.

[0062] [Table 1]

[0063]

[0064] In Example 1, in which the first separator and the second separator use separator A and separator B respectively, no defects occurred in the withstand voltage test, and even the impact test with a drop height of 80 cm of the weight was good. In addition, in the impact test with a drop height of 61 cm of the weight, all the embodiments and comparative examples were good, but in the impact test with a drop height of 80 cm of the weight, Comparative Example 2, which used separator B with high puncture strength but not too high elongation in the winding axis direction on the inner and outer sides of the positive electrode roll, was bad. It can be considered that the separator did not fully elongate when the cylindrical secondary battery was impacted, so a defect occurred in Comparative Example 2. In addition, with respect to the withstand voltage test, defects occurred in Comparative Examples 1 to 3, especially in Comparative Examples 1 and 3 where separator A with low puncture strength was provided on the inner side of the positive electrode roll, the defect was significant. In this way, it was confirmed that good results were obtained in the withstand voltage test and the impact test by arranging the two separators in a well-balanced manner on the inner and outer sides of the positive electrode roll.

[0065] Description of Reference Numerals

[0066] 10: non-aqueous electrolyte secondary battery, 11: positive electrode, 12: negative electrode, 13a: first separator, 13b: second 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 portion, 23: filter, 24: lower valve body, 25: insulating member, 26: upper valve body, 27: cap, 28: sealing gasket.

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 first separator and a second separator interposed therebetween; and a battery case, the battery case housing the electrode body, The first separator is disposed outside the roll of the positive electrode. The second separator is disposed inside the roll of the positive electrode. The puncture strength of the second spacer is higher than the puncture strength of the first spacer, The wound electrode body is wound by stacking the second separator, the positive electrode, the first separator, and the negative electrode in this order from the inner side of the roll. The first spacer has a puncture strength of 3.0 N or more and less than 3.9 N, and an elongation in the winding axis direction of 185% or more and 260% or less. The second separator has a puncture strength of 3.9 N to 6.0 N, and an elongation in a winding axis direction of 170% to 240%.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein The positive electrode has a positive electrode active material layer containing a positive electrode active material on at least one surface. The positive electrode active material is a lithium-containing composite oxide.

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