Cylindrical nonaqueous electrolyte secondary battery

Abstract

A non-aqueous electrolyte secondary battery according to one embodiment of the present invention is provided with: an electrode body in which a positive electrode (11) and a negative electrode (12) are wound; and a bottomed cylindrical outer can that accommodates the electrode body. The negative electrode (12) includes a non-facing portion (12a) that is wound by at least 1.25 circles without facing the positive electrode (11), and the non-facing portion (12a) has: a negative electrode mixture layer forming portion (12c) that is wound by at least 0.5 circles and in which a negative electrode mixture layer (41) is formed on at least one surface of a negative electrode core (40) continuously from a winding outer end toward a winding inner end side; and a negative electrode core exposed portion (12d) in which the negative electrode mixture layer (41) is not formed on both surfaces of the negative electrode core (40) continuously from the winding inner end toward the winding outer end side. A negative electrode lead (21) is connected to the negative electrode core exposed portion (12d), and the average thickness of a protruding portion (21a) protruding from the negative electrode core exposed portion (12d) toward the bottom of the outer can is larger than the average thickness of a connecting portion (21b) connected to the negative electrode core exposed portion (12d).

Description

Technical Field

[0001] The present invention relates to a cylindrical non-aqueous electrolyte secondary battery. Background Art

[0002] A cylindrical non-aqueous electrolyte secondary battery is configured to include an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween, and the electrode body is housed in an outer packaging can. In Patent Document 1, there is disclosed a non-aqueous electrolyte secondary battery in which the negative electrode has a non-opposing portion that does not oppose the positive electrode on the inner winding end side of the electrode body, and the non-opposing portion exists for two or more turns.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-137946 Summary of the Invention

[0006] The hollow portion of the core part of a cylindrical non-aqueous electrolyte secondary battery can function as an exhaust path when discharging the gas inside the battery to the outside. Therefore, it is preferable to increase the empty volume of the core part to sufficiently ensure the exhaust path. However, when a negative electrode lead is provided in the core part, the empty volume of the core part decreases. In this case, as a method of sufficiently ensuring the exhaust path, a method of thinning the negative electrode lead provided in the core part and increasing the empty volume of the core part can be considered. However, if the negative electrode lead is thinned, the resistance of the negative electrode lead increases and the Joule heat generation becomes larger. In a cylindrical non-aqueous electrolyte secondary battery, it is an important issue to suppress Joule heat generation and smoothly discharge the gas inside the battery to the outside.

[0007] The non-aqueous electrolyte secondary battery of the present invention is characterized in that it includes an electrode body formed by winding a positive electrode and a negative electrode having a negative electrode mixture layer formed on a negative electrode core body with a separator interposed therebetween, a non-aqueous electrolyte, and a bottomed cylindrical outer packaging can housing the electrode body and the non-aqueous electrolyte. The negative electrode includes a non-opposing portion that is wound for 1.25 turns or more without opposing the positive electrode with a separator interposed therebetween on the inner winding end side of the electrode body. The non-opposing portion has: a negative electrode mixture layer forming portion that continuously forms a negative electrode mixture layer on at least one surface of the negative electrode core body from the outer winding end to the inner winding end side of the non-opposing portion and is wound for 0.5 turns or more; and a negative electrode core body exposed portion that continuously does not form a negative electrode mixture layer on both surfaces of the negative electrode core body from the inner winding end to the outer winding end side of the non-opposing portion. A negative electrode lead is connected to the negative electrode core body exposed portion. The negative electrode lead has a protruding portion that protrudes from the negative electrode core body exposed portion toward the bottom side of the outer packaging can and a connecting portion that is connected to the negative electrode core body exposed portion. The average thickness of the protruding portion is greater than the average thickness of the connecting portion.

[0008] The cylindrical non-aqueous electrolyte secondary battery according to the present invention can smoothly discharge the gas inside the battery to the outside while suppressing Joule heat generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 FIG. is an axial sectional view of a cylindrical non-aqueous electrolyte secondary battery as an example of an embodiment.

[0010] Figure 2 FIG. is a plan view showing a winding structure on the inner winding end side of an electrode body as an example of an embodiment.

[0011] Figure 3 FIG. is a view showing a part of the inner winding end side of an electrode body as an example of an embodiment in an unfolded state.

[0012] Figure 4 is Figure 3 a sectional view taken along line AA in

[0013] Figure 5 FIG. is a view corresponding to Figure 4 in another example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] The inventors of the present invention conducted in-depth research and found that by changing the thickness of the negative electrode lead in the axial direction of the battery, the gas inside the battery can be smoothly discharged to the outside while suppressing Joule heat generation. Specifically, the average thickness of the protruding portion of the negative electrode lead that protrudes from the electrode body toward the bottom side of the outer packaging can is made larger than the average thickness of the connection portion connected to the negative electrode. In this case, it is possible to reduce the resistance of the negative electrode lead on the bottom side of the outer packaging can where the current density is high and increase the empty volume of the wound core portion of the electrode body.

[0015] Hereinafter, with reference to the drawings, an example of an embodiment of the cylindrical non-aqueous electrolyte secondary battery of the present invention will be described in detail. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. In addition, a mode in which the constituent elements of the following-described embodiment are selectively combined is included in the present invention.

[0016] Figure 1 FIG. schematically shows a cross section of a cylindrical non-aqueous electrolyte secondary battery (hereinafter simply referred to as a battery) 10 as an example of an embodiment. As Figure 1As shown, the battery 10 includes an electrode body 14, a non-aqueous electrolyte (not shown), and an outer packaging can 16 that houses the electrode body 14 and the non-aqueous electrolyte. The electrode body 14 has a structure including a positive electrode 11, a negative electrode 12, and a separator 13, and the positive electrode 11 and the negative electrode 12 are wound in a spiral shape with the separator 13 interposed therebetween. The outer packaging can 16 is a bottomed cylindrical metal container that is open on one axial side, and the opening of the outer packaging can 16 is sealed by a sealing body 17. It should be noted that Figure 1 in, in order to easily understand the configuration relationship of the positive electrode 11, negative electrode 12, and separator 13 in the electrode body 14, it is shown with a reduced number of windings compared to the actual situation. Hereinafter, the side of the sealing body 17 in the axial direction (height direction) of the battery 10 is set as "upper", and the bottom side of the outer packaging can 16 in the axial direction is set as "lower".

[0017] The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, for example, esters, ethers, nitriles, amides, and a mixed solvent of two or more thereof can be used. The non-aqueous solvent may also contain a halogen-substituted product in which at least a part of the hydrogen atoms of these solvents is substituted with a halogen atom such as fluorine. It should be noted that the non-aqueous electrolyte is not limited to a liquid electrolyte, and may also be a solid electrolyte using a gel-like polymer or the like. The electrolyte salt uses LiPF 6 and other lithium salts.

[0018] The positive electrode 11, negative electrode 12, and separator 13 that constitute the electrode body 14 are all strip-shaped long objects, wound in a spiral shape, and thus alternately laminated in the radial direction of the electrode body 14. In order to prevent the precipitation of lithium, the negative electrode 12 is formed with a size one turn larger than that of the positive electrode 11. That is, the negative electrode 12 is formed longer than the positive electrode 11 in the length direction and the width direction (short side direction). The separator 13 is formed with a size at least one turn larger than that of the positive electrode 11, and two sheets are arranged in a manner of sandwiching the positive electrode 11. The battery 10 includes insulating plates 18 and 19 respectively arranged above and below the electrode body 14.

[0019] The positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. As the positive electrode core 30, a foil of a metal such as aluminum or aluminum alloy that is stable in the potential range of the positive electrode 11, a film having the metal disposed on the surface, or the like can be used. The positive electrode mixture layer 31 includes a positive electrode active material, a conductive agent, and a binder. For example, a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc. is coated on the positive electrode core 30, and after the coating film is dried, it is compressed to form the positive electrode mixture layer 31 on both sides of the positive electrode core 30, whereby the positive electrode 11 can be manufactured.

[0020] The positive electrode mixture layer 31 contains particulate lithium metal composite oxide as the positive electrode active material. The lithium metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal elements constituting the lithium metal composite oxide are, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among them, it is preferable to contain at least one selected from Co, Ni, Al, and Mn. As an example of a suitable composite oxide, a lithium metal composite oxide containing Ni, Co, and Mn, and a lithium metal composite oxide containing Ni, Co, and Al can be cited.

[0021] As the conductive agent contained in the positive electrode mixture layer 31, carbon blacks such as acetylene black and Ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, and other carbon materials can be exemplified. As the binder contained in the positive electrode mixture layer 31, fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resins, polyolefins, and the like can be exemplified. In addition, these resins can be used in combination with carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), and the like.

[0022] The negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. As the negative electrode core 40, a foil of a metal stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film having the metal disposed on the surface layer can be used. The negative electrode mixture layer 41 contains a negative electrode active material, a binder, and a conductive agent used as needed. By applying a negative electrode mixture slurry containing a negative electrode active material and a binder and the like to the surface of the negative electrode core 40, drying the coating film, and then compressing it, the negative electrode mixture layer 41 can be formed on both sides of the negative electrode core 40, thereby manufacturing the negative electrode 12.

[0023] In the negative electrode mixture layer 41, as the negative electrode active material, a carbon material that reversibly occludes and releases lithium ions is generally contained. A suitable example of the carbon material is natural graphite such as flake graphite, massive graphite, and earthy graphite, artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microspheres (MCMB). In addition, as the negative electrode active material, a material containing at least one of elements that alloy with Li, such as Si and Sn, and a material containing the element can also be used. Among them, a composite material containing Si is preferable.

[0024] As a suitable example of the composite material containing Si, one can cite SiO 2Materials such as those in which Si particles are dispersed in a silicate phase such as lithium metasilicate, or materials in which Si particles are dispersed in an amorphous carbon phase. On the surface of the particles of such a composite material, a conductive layer such as a carbon coating is formed, for example. From the viewpoint of achieving both high capacity and high durability of the battery, it is preferable to use a carbon material and a composite material containing Si as the negative electrode active material.

[0025] The binder contained in the negative electrode mixture layer 41 can also be a fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc., in the same manner as in the case of the positive electrode mixture layer 31, and styrene-butadiene rubber (SBR) is preferably used. In addition, the negative electrode mixture layer 41 preferably contains CMC or its salt, polyacrylic acid (PAA) or its salt, polyvinyl alcohol (PVA), etc. Among them, it is suitable to use SBR in combination with CMC or its salt, PAA or its salt, etc. In the negative electrode mixture layer 41, a conductive agent such as CNT can also be contained.

[0026] The spacer 13 uses a porous sheet having ion permeability and insulation. Specific examples of the porous sheet include microporous films, woven fabrics, non-woven fabrics, etc. As the material of the spacer 13, polyolefins such as polyethylene and polypropylene, cellulose, etc. are suitable. The spacer 13 can have a single-layer structure or a multilayer structure. In addition, on the surface of the spacer 13, a resin layer with high heat resistance such as an aromatic polyamide resin can be formed. On the interface between the spacer 13 and at least one of the positive electrode 11 and the negative electrode 12, a filler layer containing an inorganic filler can be formed.

[0027] A positive electrode lead 20 is connected to the positive electrode 11, and a negative electrode lead 21 is connected to the inner winding end side of the negative electrode 12. The positive electrode lead 20 extends toward the sealing body 17 through the through hole of the insulating plate 18, and the negative electrode lead 21 extends toward the bottom side of the outer packaging can 16 through the through hole of the insulating plate 19. The positive electrode lead 20 is connected to the lower surface of the internal terminal plate 23 inside the sealing body 17 by welding or the like. The cap 27 forming the top plate of the sealing body 17 is electrically connected to the internal terminal plate 23, and the cap 27 becomes the positive terminal. In addition, the negative electrode lead 21 is connected to the inner surface of the bottom of the metal outer packaging can 16 by welding or the like, and the outer packaging can 16 becomes the negative terminal.

[0028] In the present embodiment, the negative electrode lead 21 is electrically connected to the inner winding end side of the negative electrode 12, and the negative electrode core 40 on the outer winding end side of the negative electrode 12 abuts against the inner surface of the outer packaging can 16. By electrically connecting both the inner winding end side and the outer winding end side of the negative electrode 12 to the negative terminal in this way, the current path is shortened and the resistance is reduced. It should be noted that instead of making the negative electrode core 40 on the outer winding end side of the negative electrode 12 abut against the inner surface of the outer packaging can 16, one negative electrode lead 21 can be electrically connected to the inner winding end side of the negative electrode 12.

[0029] As described above, the outer packaging can 16 is a metal container having a bottomed cylindrical shape with an opening on one axial side. A gasket 28 is provided between the outer packaging can 16 and the sealing body 17 to ensure the airtightness inside the battery and the insulation between the outer packaging can 16 and the sealing body 17. A slotted portion 22 for supporting the sealing body 17 is formed in a part of the side surface of the outer packaging can 16 so as to bulge inward. The slotted portion 22 is preferably formed in a ring shape along the circumferential direction of the outer packaging can 16, and the sealing body 17 is supported by its upper surface. The sealing body 17 is fixed to the upper part of the outer packaging can 16 by the slotted portion 22 and the opening end portion of the outer packaging can 16 that is caulked to the sealing body 17.

[0030] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are laminated in sequence from the side of the electrode body 14. Each member constituting the sealing body 17 has, for example, a disc shape or a ring shape, and the members other than the insulating member 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected at their respective central portions, and the insulating member 25 is interposed between their respective peripheral portions. When an abnormality occurs in the battery 10 and the internal pressure rises, the lower valve body 24 deforms and breaks in a manner of pushing the upper valve body 26 toward the cap 27 side, thereby blocking the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure further rises, the upper valve body 26 breaks, and gas is discharged from the opening portion of the cap 27.

[0031] Hereinafter, the electrode body 14 will be described in detail with reference to Figures 2 to 5 while.

[0032] Figure 2 is a plan view showing the winding structure of the winding inner end side of the electrode body 14. Figure 3 is a view showing the opposed relationship between the positive electrode 11 and the negative electrode 12 by developing a part of the winding inner end side of the electrode body 14. It should be noted that Figure 2 In, in order to easily understand the arrangement relationship, the negative electrode 12 is represented by a solid line, the positive electrode 11 is represented by a dotted line, and the spacer 13 is represented by a single dotted line. In addition, Figure 2 In, the gaps between the positive electrode 11, the negative electrode 12, and the spacer 13 are exaggeratedly represented.

[0033] As Figure 2 and Figure 3 shown, on the winding inner end side of the electrode body 14, only the negative electrode 12 among the positive electrode 11 and the negative electrode 12 is arranged. Specifically, the negative electrode 12 includes a non-opposed portion 12a that is wound more than 1.25 turns in a state of not being opposed to the positive electrode 11 with the spacer 13 interposed therebetween on the winding inner end side of the electrode body 14. The winding inner end E1 of the non-opposed portion 12a coincides with the winding inner end of the negative electrode 12. The non-opposed portion 12a is preferably wound 2 turns or less, more preferably 1.5 turns or less. In the present embodiment, as Figure 2As shown, the negative electrode 12 includes a non-opposing portion 12a wound 1.5 turns from the winding inner end E1 and an opposing portion 12b continuously wound from the winding outer end E2 of the non-opposing portion 12a and opposing the positive electrode 11 with the spacer 13 interposed therebetween.

[0034] The non-opposing portion 12a has a negative electrode mixture layer forming portion 12c and a negative electrode core exposing portion 12d. The negative electrode mixture layer forming portion 12c is a portion where a negative electrode mixture layer 41 is continuously formed on at least one surface of the negative electrode core 40 from the winding outer end E2 of the non-opposing portion 12a toward the winding inner end E1 side. The negative electrode core exposing portion 12d is a portion where the negative electrode mixture layer 41 is not formed on both surfaces of the negative electrode core 40 continuously from the winding inner end E1 toward the winding outer end E2 side. A negative electrode lead 21 is connected to the winding inner surface of the negative electrode core exposing portion 12d. It should be noted that Figure 2 in the figure, the negative electrode mixture layer forming portion 12c is represented by a thick solid line, and the negative electrode core exposing portion 12d is represented by a thin solid line.

[0035] The negative electrode mixture layer forming portion 12c is wound more than 0.5 turn, preferably more than 0.75 turn. Since the negative electrode mixture layer forming portion 12c does not oppose the positive electrode 11 on both surfaces, no charge-discharge reaction occurs in the negative electrode mixture layer forming portion 12c. Thus, the negative electrode mixture layer forming portion 12c is not easily deformed along with charge and discharge. In addition, the negative electrode mixture layer forming portion 12c has higher strength than the negative electrode core exposing portion 12d where only the negative electrode core is exposed on both surfaces. Thus, the winding core portion including the negative electrode mixture layer forming portion 12c becomes an exhaust passage, and can direct the gas generated during abnormal heating of the battery or the like to the sealing body 17 side having the upper valve body 26 as an explosion-proof valve, and exhaust efficiently. The explosion-proof valve can be provided at the bottom of the outer packaging can 16.

[0036] As Figure 3 shown, the negative electrode lead 21 is connected to the negative electrode core exposing portion 12d. The negative electrode lead 21 has a protruding portion 21a protruding downward from the negative electrode core exposing portion 12d and a connecting portion 21b connected to the negative electrode core exposing portion 12d. The length of the protruding portion 21a is not particularly limited, for example, it is 5 mm or more and 15 mm or less. Regarding the length of the connecting portion 21b, from the viewpoint of improving the bonding strength between the negative electrode 12 and the negative electrode lead 21, it is preferably 50% or more of the width of the negative electrode 12, more preferably 70% or more. The connecting portion 21b can be determined as the portion of the negative electrode lead 21 that can be connected to the negative electrode core exposing portion 12d, that is, as the portion of the negative electrode lead 21 that opposes the negative electrode core exposing portion 12d.

[0037] Here, the average thickness of the protruding portion 21a is greater than the average thickness of the connecting portion 21b. By making the average thickness of the protruding portion 21a greater than the average thickness of the connecting portion 21b, the resistance of the negative electrode lead 21 on the lower side with a high current density is reduced, and Joule heat generation can be suppressed. In addition, by making the average thickness of the connecting portion 21b smaller than the average thickness of the protruding portion 21a, the empty volume of the wound core portion of the electrode body 14 increases, and the gas generated inside the battery can be smoothly discharged to the outside.

[0038] Regarding the average thickness of the protruding portion 21a, from the viewpoint of reducing the resistance of the negative electrode lead 21, it is preferably 120% or more, more preferably 150% or more of the average thickness of the connecting portion 21b. The average thickness of the protruding portion 21a is, for example, 50 μm or more and 250 μm or less. It should be noted that the so-called average thickness of the protruding portion 21a and the connecting portion 21b is the average value when the thickness is measured at 1 mm intervals in the vertical direction of the battery using a laser displacement meter at the ends of each part.

[0039] Figure 4 is Figure 3 a cross-sectional view taken along the AA line in, and is a diagram schematically showing the thickness of the negative electrode lead 21. As Figure 4 shown, in the connecting portion 21b, an inclined region 21c in which the thickness continuously increases as it approaches the lower side of the battery 10 is provided. The inclination angle of the inclined region 21c with respect to the extending direction of the negative electrode lead 21 (hereinafter simply referred to as the inclination angle) is not particularly limited, and is, for example, 0.05° or more and 0.5° or less. By providing the inclined region 21c in the connecting portion 21b, the gas generated inside the battery is discharged to the outside along the inclined region 21c. In addition, by providing the inclined region 21c, the stress concentration at the portion where the thickness of the negative electrode lead 21 changes is alleviated, and the breakage of the negative electrode lead 21 is suppressed. In the present embodiment, as Figure 4 shown, the inclined region 21c is provided so as to straddle the protruding portion 21a and the connecting portion 21b. That is, the upper end of the connecting portion 21b is the starting point of the inclined region 21c, and the lower end of the protruding portion 21a is the ending point of the inclined region 21c.

[0040] In the present embodiment, the inclined region 21c is provided so as to straddle the protruding portion 21a and the connecting portion 21b, but it is not limited thereto. For example, the inclined region 21c may be provided only in the connecting portion 21b. In addition, the inclined region 21c may be provided throughout the connecting portion 21b, or may be provided only in a part of the connecting portion 21b as Figure 5 shown.

[0041] In addition, in the present embodiment, the inclination angle of the inclined region 21c is constant, but it is not limited thereto. For example, an inclined region 21c having a plurality of inclination angles may be provided. In the case of providing an inclined region 21c having a plurality of inclination angles, it is preferable that the inclination angle of the inclined region 21c located on the upper side of the battery is smaller than the inclination angle of the inclined region 21c located on the lower side of the battery. Thus, the gas generated inside the battery effectively discharges to the outside along the inclined region 21c.

[0042] In addition, in the present embodiment, the average thickness of the protruding portion 21a is made larger than the average thickness of the connecting portion 21b by providing the inclined region 21c, but it is not limited thereto. For example, the average thickness of the protruding portion 21a may also be made larger than the average thickness of the connecting portion 21b by providing a height difference in the connecting portion 21b.

[0043] Examples

[0044] Hereinafter, the present invention will be further described using examples, but the present invention is not limited to these examples.

[0045] <Example 1>

[0046] [Manufacture of positive electrode]

[0047] Lithium nickel cobalt aluminate (LiNi 0.88 Co 0.09 Al 0.03 O 2 ) containing aluminum is used as the positive electrode active material. 100 parts by mass of LiNi 0.88 Co 0.09 Al 0.03 O 2 as the positive electrode active material, 1.0 part by mass of acetylene black as the conductive agent, and 0.9 part by mass of polyvinylidene fluoride (PVDF) as the binder are mixed in a dispersion medium of N-methylpyrrolidone (NMP) to produce a positive electrode mixture paste. The produced positive electrode mixture paste is uniformly coated on both sides of the positive electrode core body of an aluminum foil with a thickness of 15 μm. Then, after removing NMP at a temperature of 100 to 150 °C in a dryer, it is compressed using a roll press to produce a positive electrode plate. The positive electrode plate is cut into a thickness of 0.144 mm, a width of 62.6 mm, and a length of 860 mm to produce a positive electrode.

[0048] [Manufacture of negative electrode]

[0049] The negative electrode active material is produced by mixing 95 parts by mass of graphite powder and 5 parts by mass of Si oxide. 100 parts by mass of the negative electrode active material, 1 part by mass of CMC as a thickener, and 1 part by mass of styrene-butadiene rubber as a binder are mixed in water to produce a negative electrode mixture slurry. The negative electrode mixture slurry is coated on both sides of a negative electrode core body made of a copper foil with a thickness of 8 μm to form a negative electrode mixture layer. Then, after drying, compression is performed using a compression roller so that the negative electrode thickness is 0.160 mm to produce a negative electrode. The negative electrode plate is cut to a width of 64.2 mm and a length of 959 mm to produce a negative electrode.

[0050] [Mounting of negative electrode lead]

[0051] As Figure 4 shown, a nickel negative electrode lead with a thickness of 100 μm at the upper end and 200 μm at the lower end, and the thickness continuously increasing from the upper end to the lower end, is mounted on the exposed portion of the negative electrode core body on the inner winding side of the negative electrode. The length of the protruding portion is 10 mm, and the length of the connecting portion is 60 mm. The average thickness of the protruding portion in Example 1 is 193 μm, and the average thickness of the connecting portion is 143 μm.

[0052] [Fabrication of electrode body]

[0053] The positive electrode and the negative electrode are wound with a polyethylene spacer interposed therebetween, and a polypropylene (PP) tape with a width of 12 mm, a thickness of 30 μm, and a length of 50.0 mm is pasted within 10 mm from both ends of the electrode body on the outermost periphery to produce an electrode body. At this time, the winding structure on the inner winding side of the electrode body is fabricated in such a way as to be the Figure 2 structure shown, and the exposed portion of the negative electrode core body is disposed on the outermost peripheral surface of the electrode body.

[0054] [Preparation of non-aqueous electrolyte]

[0055] 5 parts by mass of vinylene carbonate (VC) is added to 100 parts by mass of a mixed solvent composed of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC:DMC = 1:3 by volume ratio), and LiPF is dissolved at 1.5 mol / L 6 to prepare a non-aqueous electrolyte.

[0056] [Fabrication of non-aqueous electrolyte secondary battery]

[0057] Insulating plates are disposed above and below the electrode body, the negative electrode lead is welded to the outer packaging can, and the positive electrode lead is welded to a sealing body having an internal pressure-operated explosion-proof valve, and then it is housed inside the outer packaging can. After that, the non-aqueous electrolyte is injected into the inside of the outer packaging can by a decompression method. Finally, the opening end of the outer packaging can is caulked to the sealing plate with a gasket interposed therebetween, thereby fabricating a cylindrical non-aqueous electrolyte secondary battery. The capacity of the battery is 4600 mAh.

[0058] <Example 2>

[0059] As Figure 5 shown, a nickel negative electrode lead having thicknesses of 100 μm at the upper end and 200 μm at the lower end, and the thickness continuously increasing from the central portion of the negative electrode lead to the lower end, is attached to the exposed portion of the negative electrode core body on the inner end side of the winding of the negative electrode. The average thickness of the protruding portion in Example 2 is 186 μm, and the average thickness of the connecting portion is 115 μm. The other configurations are the same as those in Example 1.

[0060] <Example 3>

[0061] As Figure 5 shown, a nickel negative electrode lead having thicknesses of 100 μm at the upper end and 250 μm at the lower end, and the thickness continuously increasing from the central portion to the lower end, is attached to the exposed portion of the negative electrode core body on the inner end side of the winding of the negative electrode. The average thickness of the protruding portion in Example 3 is 229 μm, and the average thickness of the connecting portion is 122 μm. The other configurations are the same as those in Example 1.

[0062] <Comparative Example 1>

[0063] A nickel negative electrode lead having a uniform thickness of 200 μm is attached to the exposed portion of the negative electrode core body on the inner end side of the winding of the negative electrode. The other configurations are the same as those in Example 1.

[0064] <Comparative Example 2>

[0065] A nickel negative electrode lead having a uniform thickness of 150 μm is attached to the exposed portion of the negative electrode core body on the inner end side of the winding of the negative electrode. The other configurations are the same as those in Example 1.

[0066] The empty volume of the wound core portion of the batteries in the examples and comparative examples and the resistance per unit length of the protruding portion are shown in Table 1. It should be noted that the empty volume of the wound core portion of the batteries in Table 1 and the resistance per unit length of the protruding portion are relative values with the battery in Comparative Example 1 set to 100. In addition, the smaller the value of the resistance per unit length of the protruding portion, the lower the resistance.

[0067]

[0068] As shown in Table 1, in the batteries of Example 1 and Example 2, the resistance is equivalent to that of the battery in Comparative Example 1, and the empty volume of the wound core portion increases compared to the battery in Comparative Example 1. In addition, in the battery of Example 3, the resistance decreases compared to the battery in Comparative Example 1, and the empty volume of the wound core portion increases compared to the battery in Comparative Example 1. On the other hand, in the battery of Comparative Example 2, although the empty volume of the wound core portion increases compared to the battery in Comparative Example 1, the resistance increases significantly.

[0069] From the above test results, it can be seen that by making the average thickness of the protruding portion greater than the average thickness of the connecting portion, it is possible to increase the void volume of the wound core portion while suppressing the increase in the resistance of the negative electrode lead of the protruding portion, and smoothly discharge the gas inside the battery to the outside.

[0070] Description of Reference Numerals

[0071] 10 Battery (non-aqueous electrolyte secondary battery), 11 Positive electrode, 12 Negative electrode, 12a Non-opposing portion, 12b Opposing portion, 12c Negative electrode mixture layer forming portion, 12d Negative electrode core exposed portion, 13 Spacer, 14 Electrode body, 16 Outer packaging can, 17 Sealing body, 18, 19 Insulating plates, 20 Positive electrode lead, 21 Negative electrode lead, 21a Protruding portion, 21b Connecting portion, 21c Inclined region, 22 Slotted portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core, 31 Positive electrode mixture layer, 40 Negative electrode core, 41 Negative electrode mixture layer.

Claims

1. A cylindrical non-aqueous electrolyte secondary battery, comprising an electrode body formed by winding a positive electrode and a negative electrode with a negative electrode mixture layer formed on a negative electrode core body with a separator interposed therebetween, a non-aqueous electrolyte, and a bottomed cylindrical outer packaging can for housing the electrode body and the non-aqueous electrolyte, the negative electrode includes a non-opposing portion wound more than 1.25 turns on the winding inner end side of the electrode body without opposing the positive electrode with the separator interposed therebetween, the non-opposing portion has: a negative electrode mixture layer forming portion, which continuously forms the negative electrode mixture layer on at least one surface of the negative electrode core body from the winding outer end to the winding inner end side of the non-opposing portion and winds more than 0.5 turn; and a negative electrode core body exposed portion, which continuously does not form the negative electrode mixture layer on both surfaces of the negative electrode core body from the winding inner end to the winding outer end side of the non-opposing portion, a negative electrode lead is connected to the negative electrode core body exposed portion, the negative electrode lead has a protruding portion protruding from the negative electrode core body exposed portion toward the bottom side of the outer packaging can and a connecting portion connected to the negative electrode core body exposed portion, the average thickness of the protruding portion is greater than the average thickness of the connecting portion.

2. The cylindrical non-aqueous electrolyte secondary battery according to claim 1, wherein, the average thickness of the protruding portion is 120% or more of the average thickness of the connecting portion.

3. The cylindrical non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein, an inclined region where the thickness continuously increases is provided in the connecting portion as it approaches the bottom side of the outer packaging can.

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