Non-aqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery characterized by having an electrode body (14) in which a strip-shaped positive electrode (11) and a strip-shaped negative electrode (12) are wound along the length direction with a separator (13) interposed, the positive electrode (11) having a positive electrode current collector exposed portion in which a positive electrode current collector (30) is exposed without a positive electrode mixture layer (31) being provided, a positive electrode tab (20) being joined to the positive electrode current collector exposed portion, the negative electrode (12) having a negative electrode current collector exposed portion in which a negative electrode current collector (40) is exposed without a negative electrode mixture layer (41) being provided, a negative electrode tab (21) being joined to the negative electrode current collector exposed portion, the positive electrode tab (20) and the negative electrode tab (21) being disposed apart by a gap in the axial direction of the electrode body (14), the gap being disposed at a position that does not overlap with the central portion in the axial direction of the electrode body (14).

Description

Technical Field

[0001] This invention relates to a non-aqueous electrolyte secondary battery. Background Technology

[0002] Previously, non-aqueous electrolyte secondary batteries were known to have an electrode body formed by winding a positive electrode and a negative electrode with a spacer between them, and an outer packaging can containing the electrode body. Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which a positive electrode tab connected to the positive electrode and a negative electrode tab connected to the negative electrode are located approximately at the center of the radial direction of the electrode body.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: U.S. Patent Application Publication No. 2021 / 023044 Summary of the Invention

[0006] However, when a load is applied to a non-aqueous electrolyte secondary battery from the outside, the axial central portion of the battery tends to deform more easily than the two axial ends. The non-aqueous electrolyte secondary battery disclosed in Patent Document 1 only has positive and negative electrode tabs arranged within a limited range at both axial ends of the electrode body. Therefore, the strength of the axial central portion of the battery is insufficient, and it is prone to deformation when an external load is applied.

[0007] The non-aqueous electrolyte secondary battery, as an embodiment of the present invention, is characterized by comprising an electrode body formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode along the length direction with a spacer between them, and a bottomed cylindrical outer packaging can containing the electrode body. The positive electrode has a positive electrode current collector exposed portion without a positive electrode binder layer, and the negative electrode has a negative electrode current collector exposed portion without a negative electrode binder layer. A positive electrode tab protruding from one of the two ends of the electrode body is joined in the positive electrode current collector exposed portion, and a negative electrode tab protruding from the other end of the two ends of the electrode body is joined in the negative electrode current collector exposed portion. The negative electrode current collector exposed portion is located in a region where at least a portion of it overlaps with an opposing region in the width direction of the negative electrode. The opposing region is the region of the negative electrode opposite to the positive electrode current collector exposed portion with the aforementioned spacer between them. Viewed radially from the electrode body, the positive electrode tab and the negative electrode tab are provided with a gap along the axial direction of the electrode body, and the gap is located at a position that does not overlap with the axial center of the electrode body.

[0008] According to the non-aqueous electrolyte secondary battery, which is one aspect of the present invention, it is possible to suppress battery deformation caused by externally applied loads. Attached Figure Description

[0009] Figure 1This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery as an example of an implementation method.

[0010] Figure 2 This is a front view of the positive and negative electrodes of a non-aqueous electrolyte secondary battery, shown in its unfolded state as an example of an embodiment.

[0011] Figure 3 yes Figure 1 The diagram shows a cross-sectional view along line AA, with an enlarged view of the vicinity of the positive electrode tab.

[0012] Figure 4 yes Figure 1 The BB line cross-sectional view is a magnified view of the vicinity of the negative electrode tab.

[0013] Figure 5 This is a front view of the positive and negative electrodes of a non-aqueous electrolyte secondary battery, shown in its unfolded state as another example of an implementation. Detailed Implementation

[0014] Hereinafter, an example embodiment of the non-aqueous 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, values, orientations, etc., are examples used to facilitate understanding of the present invention and can be appropriately varied according to the specifications of the non-aqueous electrolyte secondary battery. Furthermore, in the following description, where multiple embodiments and modifications are included, it is initially conceived that their characteristic parts are appropriately combined.

[0015] Figure 1 This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery 10, as an example of an embodiment. (See attached image.) Figure 1 As shown, the non-aqueous electrolyte secondary battery 10 includes a wound electrode body 14, a non-aqueous electrolyte (not shown), and an outer packaging can 16 for housing the electrode body 14 and the non-aqueous electrolyte. The outer packaging can 16 is a bottomed cylindrical metal container with an opening on one axial side, and the opening of the outer packaging can 16 is sealed by a sealing body 17. Hereinafter, for ease of explanation, the sealing body 17 side of the battery will be referred to as "upper" and the bottom side of the outer packaging can 16 will be referred to as "lower".

[0016] The electrode body 14 has a structure in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound together along the length direction, with a spacer 13 in between. The positive electrode 11, negative electrode 12, and spacer 13 are wound into a spiral shape and are stacked alternately in the radial direction of the electrode body 14. In the electrode body 14, the length direction of the positive electrode 11 and negative electrode 12 is the winding direction, and the width direction of the positive electrode 11 and negative electrode 12 is the axial direction. In addition, the non-aqueous electrolyte secondary battery 10 further includes a positive electrode tab 20 that is connected to the positive electrode 11 by welding or the like and protrudes from the upper end of the electrode body 14, and a negative electrode tab 21 that is connected to the negative electrode 12 by welding or the like and protrudes from the lower end of the electrode body 14.

[0017] The positive electrode 11 has a positive current collector 30 and a positive electrode flux layer 31 disposed on the positive current collector 30. The positive current collector 30 can be a foil of a metal that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film on which such metal is disposed on the surface. The positive electrode flux layer 31 contains a positive electrode active material, a conductive agent, and a binder. For example, a positive electrode flux slurry containing a positive electrode active material, a conductive agent, and a binder can be coated on the positive current collector 30, and after the coating is dried, it is compressed to form the positive electrode flux layer 31 on both sides of the positive current collector 30, thereby manufacturing the positive electrode 11.

[0018] The positive electrode additive layer 31 contains particulate lithium-containing composite oxides as the positive electrode active material. The lithium-containing 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-containing 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. Preferably, it contains at least one selected from Co, Ni, Al, and Mn. Examples of suitable composite oxides include lithium-containing composite oxides containing Ni, Co, and Mn, and lithium-containing composite oxides containing Ni, Co, and Al.

[0019] Examples of conductive agents contained in the positive electrode binder layer 31 include carbon black such as acetylene black and Ketjen black, graphite, carbon nanotubes (CNTs), carbon nanofibers, and graphene. Examples of binders contained in the positive electrode binder layer 31 include fluorinated resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins. Additionally, these resins may be used in combination with carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0020] The negative electrode 12 has a negative electrode current collector 40 and a negative electrode binder layer 41 disposed on the negative electrode current collector 40. The negative electrode current collector 40 can be a foil of a metal that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film of such metal disposed on its surface. The negative electrode binder layer 41 contains a negative electrode active material, a binder, and a conductive agent used as needed. The negative electrode 12 can be manufactured by coating the surface of the negative electrode current collector 40 with a negative electrode binder slurry containing a negative electrode active material and a binder, drying the coating, and then compressing it.

[0021] The negative electrode composite layer 41 typically comprises a carbon material that reversibly absorbs and releases lithium ions as the negative electrode active material. Suitable examples of carbon materials include natural graphite such as flake graphite, block graphite, and amorphous graphite, as well as artificial graphite such as block graphite (MAG) and graphitized mesophase carbon microspheres (MCMB). Alternatively, materials containing at least one of elements alloyed with Li, such as Si and Sn, or materials containing these elements can also be used as the negative electrode active material. Among these, composite materials containing Si are preferred.

[0022] As the binder included in the negative electrode binder layer 41, it can also be made of fluorinated resins, PAN, polyimide, acrylic resins, polyolefins, etc., similar to the case of the positive electrode binder layer 31, with styrene-butadiene rubber (SBR) being preferred. Furthermore, the negative electrode binder layer 41 preferably includes CMC or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol (PVA), etc. It is suitable to use SBR in combination with CMC or its salts, PAA or its salts, etc. Additionally, conductive agents such as CNTs may also be included in the negative electrode binder layer 41.

[0023] The spacer 13 is made of a porous sheet that is both ion-permeable and insulating. Specific examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. Suitable materials for the spacer 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The spacer 13 can be a single-layer structure or a multi-layer structure. In addition, a resin layer with high heat resistance, such as an aromatic polyamide resin, can be formed on the surface of the spacer 13.

[0024] On the outer peripheral surface of the electrode body 14, a contact portion 43 is provided, exposing the negative electrode current collector 40 where the negative electrode binder layer 41 has not yet formed, and abutting against the inner surface of the outer packaging can 16. By providing the contact portion 43 on the outer peripheral surface of the electrode body 14 while having the negative electrode tab 21, the internal resistance of the non-aqueous electrolyte secondary battery 10 can be further reduced. It should be noted that, alternatively, a spacer 13 may be provided on the outer peripheral surface of the electrode body 14 instead of the contact portion 43.

[0025] Non-aqueous electrolytes have lithium-ion conductivity. Non-aqueous electrolytes can be liquid electrolytes (electrolytes) or solid electrolytes.

[0026] Liquid electrolytes (electrolytes) comprise a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Non-aqueous solvents include, for example, esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may contain halogen-substituted derivatives (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are replaced by halogen atoms such as fluorine. Electrolyte salts include, for example, lithium salts such as LiPF6.

[0027] As a solid electrolyte, examples include solid or gel-like polymer electrolytes and inorganic solid electrolytes. As an inorganic solid electrolyte, materials known in all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. Polymer electrolytes may contain, for example, lithium salts and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. As a matrix polymer, for example, a polymer material that gels upon absorbing a non-aqueous solvent is used. Examples of polymer materials include fluoropolymers, acrylic resins, and polyether resins.

[0028] Insulating plates 18 and 19 are respectively disposed above and below the electrode body 14. Figure 1 In the example shown, the positive electrode tab 20 extends towards the sealing body 17 after passing through the through hole in the insulating plate 18, and the negative electrode tab 21 extends towards the bottom of the outer packaging can 16 after passing through the through hole in the insulating plate 19. The positive electrode tab 20 is connected to the lower surface of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is electrically connected to the internal terminal plate 23 and serves as the top plate of the sealing body 17, becomes the positive terminal. The negative electrode tab 21 is connected to the inner bottom surface of the outer packaging can 16 by welding or the like, and the outer packaging can 16 becomes the negative terminal.

[0029] As described above, the outer packaging can 16 is a bottomed cylindrical metal container with an axially open end, and the opening of the outer packaging can 16 is sealed by a sealing body 17.

[0030] A gasket 28 is provided between the outer packaging can 16 and the sealing body 17 to ensure the airtightness of the battery interior. A slotted portion 22, formed by a portion of the surface of the outer packaging can 16 bulging inwards, supports the sealing body 17. The slotted portion 22 is preferably formed in a ring shape along the circumference of the outer packaging can 16, and its upper surface supports the sealing body 17. The sealing body 17 is fixed to the upper part of the outer packaging can 16 by the slotted portion 22 and the open end of the outer packaging can 16 that is tightly fitted to the sealing body 17.

[0031] 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 stacked sequentially from the electrode body 14 side. Each component constituting the sealing body 17 is, for example, circular or annular, and all 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 at their respective central portions, and the insulating member 25 is sandwiched between their respective peripheral portions. When the internal pressure of the battery rises due to abnormal heating, the lower valve body 24 deforms and breaks by pushing the upper valve body 26 towards the cap 27, thereby cutting off the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure rises further, the upper valve body 26 breaks, and gas is discharged from the vent of the cap 27.

[0032] Below, in further reference Figures 2-4 At the same time, the positive electrode 11 and the negative electrode 12 are described in detail. Figure 2 This is a front view showing the positive electrode 11 and the negative electrode 12 in their unfolded state. Figure 3 yes Figure 1 The AA-line cross-sectional view, and is a magnified view of the vicinity of the positive electrode tab 20. Figure 4 yes Figure 1 This is a cross-sectional view along the BB line, showing an enlarged view of the vicinity of the negative electrode tab 21. It should be noted that... Figure 2 In the diagram, (a) is a top view of the inner surface of the positive electrode 11, (b) is a top view of the outer surface of the positive electrode 11, (c) is a top view of the inner surface of the negative electrode 12, and (d) is a top view of the outer surface of the negative electrode 12.

[0033] like Figure 2 As shown, the positive electrode 11 has a positive electrode current collector 30 exposed without a positive electrode flux layer 31 (see reference). Figure 1 The positive current collector exposed portion 32 of the positive current collector 30. In this embodiment, the positive current collector exposed portion 32 includes a first positive current collector exposed portion 33 and a second positive current collector exposed portion 35. The positive current collector exposed portion 32 can be made, for example, by intermittently coating a portion of the positive current collector 30 without coating it with the positive current collector slurry.

[0034] The positive current collector exposed portion 32 is provided throughout the entire width direction of the positive electrode 11. That is, the positive current collector exposed portion 32 contacts the upper end 11A and the lower end 11B of the positive electrode 11, respectively. The first positive current collector exposed portion 33 and the second positive current collector exposed portion 35 are respectively provided on the outer and inner winding surfaces of the positive electrode 11 in a manner that overlaps each other along the thickness direction of the positive electrode 11. In this embodiment, a positive electrode tab 20 protruding from the upper end of the electrode body 14 is joined to the first positive current collector exposed portion 33. It should be noted that the positive electrode tab 20 can be joined to either the inner or outer winding surface of the first positive current collector exposed portion 33.

[0035] The first positive current collector exposed portion 33, which is connected to the positive electrode tab 20, is preferably located approximately at the center of the positive electrode 11 along its length. By providing the first positive current collector exposed portion 33 approximately at the center of the positive electrode 11 along its length, the internal resistance of the positive electrode 11 can be reduced.

[0036] like Figure 3 As shown, the first positive current collector exposed portion 33, to which the positive electrode tab 20 is attached, is positioned opposite the negative current collector exposed portion 42, separated by a spacer 13. Details will be described later. A negative electrode tab 21 is attached to the negative current collector exposed portion 42. By configuring the first positive current collector exposed portion 33, to which the positive electrode tab 20 is attached, to be positioned opposite the negative current collector exposed portion 42, separated by a spacer 13, not only can misalignment of the electrode body 14 be suppressed, but lithium deposition at the negative current collector exposed portion 42 during charging can also be suppressed. Since the negative current collector exposed portion 42 exposes the negative current collector 40 not only on the outer surface of the winding but also on the inner surface of the winding, it is preferable that the second positive current collector exposed portion 35 is positioned opposite the inner surface of the winding, separated by a spacer 13. In this case, the second positive current collector exposed portion 35 may expose the positive current collector 30 only on the outer surface of the winding. It should be noted that since insulating members 50 or the like can be used to suppress lithium deposition into the negative current collector exposed portion 42 during charging, a second positive current collector exposed portion 35 not connected to the positive electrode tab 20 is not necessarily required. The length of the positive current collector exposed portion 32 along the length direction of the positive electrode 11 is, for example, 120% or more, or 150% or more, of the length of the negative current collector exposed portion 42 along the length direction of the negative electrode 12. The length of the positive current collector exposed portion 32 along the length direction of the positive electrode 11 is, for example, 5 mm or more and 50 mm or less. It should be noted that the lengths of each positive current collector exposed portion 32 along the length direction of the positive electrode 11 may be the same or different from each other.

[0037] like Figure 2 and Figure 3As shown, an insulating member 50 is provided on the surface of the positive electrode 11 to cover the exposed portion 32 of the positive current collector. The insulating member 50 covers the entire exposed portion 32 of the positive current collector, a portion of the positive electrode tab 20, and the positive electrode binder layer 31 surrounding the exposed portion 32 of the positive current collector. By providing the insulating member 50, contact between the exposed portion 32 of the positive current collector, the positive electrode tab 20, and the negative electrode 12 can be suppressed when the spacer 13 is damaged. As a result, internal short circuits can be suppressed.

[0038] The insulating member 50 is, for example, an adhesive tape having a substrate portion and an adhesive portion formed on one surface of the substrate portion. It should be noted that a heat-resistant layer containing inorganic particles such as metal oxides may be provided between the substrate portion and the adhesive portion. The substrate portion can be made of any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), etc. The thickness of the substrate portion is, for example, 5 μm or more and 50 μm or less, preferably 10 μm or more and 30 μm or less.

[0039] The adhesive portion is used to bond the insulating member 50 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 contain at least one of a rubber-based polymer and an acrylic polymer. Because rubber-based polymers and acrylic polymers have adhesive properties, the insulating member 50 can be bonded to the surface of the positive electrode 11. The adhesive portion may further contain, for example, a silicone-based polymer.

[0040] like Figure 2 As shown, the negative electrode 12 has a negative electrode current collector 40 exposed without a negative electrode binder layer 41 (see reference). Figure 1 The negative electrode current collector exposed portion 42. The negative electrode current collector exposed portion 42 can be made, for example, by intermittently coating a portion of the negative electrode current collector 40 without coating it with the negative electrode slurry.

[0041] The exposed negative current collector 42 is provided throughout the entire width direction of the negative electrode 12. That is, the exposed negative current collector 42 contacts the upper end 12A and the lower end 12B of the negative electrode 12, respectively. The exposed negative current collector 42 is provided on the inner and outer winding surfaces of the negative electrode 12 in an overlapping manner along the thickness direction of the negative electrode 12. In this embodiment, a negative electrode tab 21 protruding from the lower end of the electrode body 14 is joined to the outer winding surface of the exposed negative current collector 42. It should be noted that the negative electrode tab 21 may also be joined to the inner winding surface of the negative electrode 12.

[0042] The exposed portion 42 of the negative current collector, which is connected to the negative electrode tab 21, is preferably located approximately at the center of the negative electrode 12 along its length. By providing the exposed portion 42 of the negative current collector 42 approximately at the center of the negative electrode 12 along its length, the internal resistance of the negative electrode 12 can be reduced. Alternatively, the exposed portion of the negative current collector may be provided at the winding start end of the negative electrode 12, in a region not opposite to the exposed portion of the positive current collector 32 separated by the spacer 13, and the negative electrode tab may be connected to this exposed portion of the negative current collector.

[0043] like Figure 2 and Figure 4 As shown, the negative current collector exposed portion 42 is provided in the region (opposing region) opposite the first positive current collector exposed portion 33 that is sandwiched between the spacer 13 and the positive electrode tab 20. As described above, if the positive electrode binder layer 31 is sandwiched between the spacer 13 and the negative current collector exposed portion 42, lithium deposition may occur in the negative current collector exposed portion 42 during charging. Therefore, from the viewpoint of preventing the positive electrode binder layer 31 and the negative current collector exposed portion 42 from being sandwiched between the spacer 13, it is preferable to configure the first positive current collector exposed portion 33, which is provided for bonding the positive electrode tab 20, to be sandwiched between the spacer 13 and the negative current collector exposed portion 42. By arranging the first positive current collector exposed portion 33 of the positive electrode tab 20 and the negative current collector exposed portion 42 of the negative electrode tab 21 opposite each other with a spacer in place, as in this embodiment, lithium deposition at the negative electrode 12 during charging can be suppressed while suppressing capacity reduction of the non-aqueous electrolyte secondary battery 10. It should be noted that the negative current collector exposed portion 42 can also be covered by the insulating member 50 in the same way as the positive current collector exposed portion 32.

[0044] like Figure 1 and Figure 2 As shown, the positive electrode tab 20 and the negative electrode tab 21 are configured to be spaced apart along the axial direction of the electrode body 14 when viewed radially from the electrode body 14. Moreover, this gap is positioned so as not to overlap with the axial center portion of the electrode body 14. That is, one of the positive electrode tab 20 and the negative electrode tab 21 is positioned to overlap with the axial center portion of the electrode body 14.

[0045] When a non-aqueous electrolyte secondary battery 10 is subjected to an external load, the axial central portion of the battery is more prone to deformation compared to the two axial end portions. Particularly when the positive electrode tab 20 and negative electrode tab 21 are respectively located at the axial ends of the electrode body 14, there is a tendency for the axial central portion of the battery to deform under external loads. By offsetting the gap between the positive electrode tab 20 and the negative electrode tab 21 from the axial central portion of the electrode body 14, as in this embodiment, and placing the positive electrode tab 20 or the negative electrode tab 21 at the axial central portion of the electrode body 14, the strength of the axial central portion of the electrode body 14 can be increased. As a result, deformation of the axial central portion of the battery caused by external loads can be suppressed.

[0046] It should be noted that when no gap is formed between the positive electrode tab 20 and the negative electrode tab 21, that is, when the positive electrode tab 20 and the negative electrode tab 21 are arranged to overlap radially along the electrode body 14, the outer diameter of the electrode body 14 will excessively increase in the area where the positive electrode tab 20 and the negative electrode tab 21 overlap. As a result, stress concentrates in the area where the positive electrode tab 20 and the negative electrode tab 21 overlap, thereby causing damage to the electrode body 14. By forming a gap between the positive electrode tab 20 and the negative electrode tab 21 as in this embodiment, and arranging the positive electrode tab 20 and the negative electrode tab 21 so that they do not overlap radially along the electrode body 14, it is possible to suppress damage to the electrode body 14 while suppressing deformation of the axial central portion of the battery caused by externally applied loads.

[0047] In this embodiment, the positive electrode tab 20 extends from the upper end of the electrode body 14 to a position beyond the axial center of the electrode body 14, and the negative electrode tab 21 extends from the lower end of the electrode body 14 to a position beyond the axial center of the electrode body 14. Therefore, a gap is formed between the positive electrode tab 20 and the negative electrode tab 21 on the lower side relative to the axial center of the electrode body 14. Generally speaking, the components used in the positive electrode tab 20 are less expensive than the components used in the negative electrode tab 21, so by making the length of the positive electrode tab 20 greater than the length of the negative electrode tab 21, it is easy to reduce the manufacturing cost of the battery.

[0048] It should be noted that the configuration relationship between the positive electrode tab 20 and the negative electrode tab 21 is not limited to... Figure 1 and Figure 2 The configuration is shown. For example, the positive electrode tab 20 may extend from the upper end of the electrode body 14 to a position not exceeding the axial center of the electrode body 14, and the negative electrode tab 21 may extend from the lower end of the electrode body 14 to a position exceeding the axial center of the electrode body 14. That is, a gap may be formed on the upper side relative to the axial center of the electrode body 14 between the positive electrode tab 20 and the negative electrode tab 21 in the axial direction of the electrode body 14.

[0049] The gap between the positive electrode tab 20 and the negative electrode tab 21 along the axial direction of the electrode body 14 is preferably provided in a range of 20% or more and less than 50% of the axial length of the electrode body 14, starting from both ends along the axial direction of the electrode body 14, and more preferably in a range of 25% or more and less than 45%. In this case, it is easy to increase the strength of the axial central portion of the electrode body 14 while connecting the positive electrode tab 20 and the negative electrode tab 21 to the positive current collector exposed portion 32 and the negative current collector exposed portion 42, respectively. It should be noted that the axial length of the electrode body 14 refers to the length along the axial direction of the electrode body 14 from the upper end to the lower end of the electrode body 14. In this embodiment, it is the length along the axial direction of the electrode body 14 from the upper end to the lower end of the spacer 13.

[0050] The length of the gap between the positive electrode tab 20 and the negative electrode tab 21 along the axial direction of the electrode body 14 is preferably 3% or more, more preferably 5% or more, of the axial length of the electrode body 14. In this case, the generation of internal short circuits caused by contact between the positive electrode tab 20 and the negative electrode tab 21 can be suppressed. Furthermore, the length of the gap between the positive electrode tab 20 and the negative electrode tab 21 along the axial direction of the electrode body 14 is preferably 30% or less, more preferably 25% or less, of the axial length of the electrode body 14. In this case, the area where the positive electrode tab 20 and the negative electrode tab 21 are disposed becomes larger, which can further increase the strength of the electrode body 14. Therefore, the length of the gap between the positive electrode tab 20 and the negative electrode tab 21 along the axial direction of the electrode body 14 is preferably 3% or more and 30% or less, more preferably 5% or more and 25% or less, of the axial length of the electrode body 14.

[0051] The first positive current collector exposed portion 33 and the negative current collector exposed portion 42, which are separated by spacer 13 and face each other, can be respectively provided at multiple positions of the positive electrode 11 and the negative electrode 12. In addition, the positive electrode 11 may have a positive current collector exposed portion other than the positive current collector exposed portion 32, and the negative electrode 12 may have a negative current collector exposed portion other than the negative current collector exposed portion 42. For example, a negative current collector exposed portion that is not separated by spacer 13 and faces the positive current collector exposed portion can be provided at the winding start end of the negative electrode 12, and a negative electrode tab can be engaged at this negative current collector exposed portion.

[0052] Below, in reference Figure 5 Meanwhile, another embodiment of the non-aqueous electrolyte secondary battery of the present invention will be described in detail. Figure 5 This is a front view showing the positive electrode 11 and the negative electrode 12 in their unfolded state. It should be noted that... Figure 5 In the diagram, (a) is a top view of the inner surface of the positive electrode 11, (b) is a top view of the outer surface of the positive electrode 11, (c) is a top view of the inner surface of the negative electrode 12, and (d) is a top view of the outer surface of the negative electrode 12.

[0053] like Figure 5 As shown, in this embodiment, the positive current collector exposed portion 32 includes a first positive current collector exposed portion 33 and a second positive current collector exposed portion 35, and further includes a third positive current collector exposed portion 37. The third positive current collector exposed portion 37 is provided on the inner and outer surfaces of the positive electrode 11 in a manner that overlaps with each other along the thickness direction of the positive electrode 11. The third positive current collector exposed portion 37 is covered by the insulating member 50 in the same manner as the other positive current collector exposed portions 32.

[0054] Furthermore, in this embodiment, the exposed positive electrode current collector 32 is not provided throughout the entire width direction of the positive electrode 11. Specifically, the first exposed positive electrode current collector 33 contacts only the upper end 11A of the positive electrode 11, and the second exposed positive electrode current collector 35 and the third exposed positive electrode current collector 37 contact only the lower end 11B of the positive electrode 11. By making the exposed positive electrode current collector 32 contact only one of the two ends in the width direction of the positive electrode 11, the volume of the positive electrode flux layer 31 can be increased, thereby facilitating the realization of high capacity in the non-aqueous electrolyte secondary battery 10.

[0055] In this embodiment, the exposed portion 42 of the negative current collector is not provided throughout the entire width direction of the negative electrode 12, but only contacts the lower end 12B of the negative electrode 12. Therefore, with Figures 2 to 4 In the different embodiments shown, the exposed negative current collector 42, which is joined with the negative electrode tab 21, does not face the first exposed positive current collector 33, which is joined with the spacer 13. However, the exposed negative current collector 42 is provided in a region that overlaps with the region (opposing region) in the width direction of the negative electrode 12 that faces the first exposed positive current collector 33, which is joined with the spacer 13. Therefore, in this embodiment, the winding misalignment of the electrode body 14 is suppressed. It should be noted that the exposed negative current collector 42 only needs to be provided in a region that overlaps with the opposing region in the width direction of the negative electrode 12. In order to suppress lithium deposition at the exposed negative current collector 42 during charging, the third exposed positive current collector 37 is configured to face the exposed negative current collector 42, which is joined with the spacer 13. Similar to the second positive current collector exposed portion 35, it is not necessarily necessary to provide a third positive current collector exposed portion 37.

[0056] Figure 5In the example shown, the positive electrode tab 20 extends from the upper end of the electrode body 14 to a position beyond the axial center of the electrode body 14, and the negative electrode tab 21 extends from the lower end of the electrode body 14 to a position not exceeding the axial center of the electrode body 14. Therefore, the first positive current collector exposed portion 33 extends from the upper end 11A of the positive electrode 11 to a position beyond the center of the width direction of the positive electrode 11, and the second positive current collector exposed portion 35 and the third positive current collector exposed portion 37 extend from the lower end 11B of the positive electrode 11 to a position not exceeding the center of the width direction of the positive electrode 11.

[0057] Example

[0058] The present invention will be further described below through embodiments; however, the present invention is not limited to these embodiments.

[0059] <Example>

[0060] [The production of the positive electrode]

[0061] Aluminum-containing lithium nickel cobalt oxide was used as the positive electrode active material. This positive electrode active material, acetylene black (AB), and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 100:2:1, and N-methyl-2-pyrrolidone (NMP) was used as the dispersion medium to prepare a positive electrode slurry. Then, the positive electrode slurry was coated on both sides of a positive electrode current collector made of 15 μm thick aluminum foil, and the coating was allowed to dry. The coating was then calendered using calendering rollers and cut to the specified electrode size to fabricate the positive electrode. At this point, as... Figure 2 As shown, four positive current collector exposed portions are respectively provided on the surface of the positive current collector, and an aluminum positive electrode tab is welded to the first positive current collector exposed portion. It should be noted that the positive electrode tab is joined to a range extending beyond the center of the positive electrode in the width direction.

[0062] [Making the negative electrode]

[0063] A negative electrode active material was prepared by mixing artificial graphite and silicon-carbon composite (SiC) at a mass ratio of 90:10. This negative electrode active material, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed at a mass ratio of 100:1:1, using water as the dispersion medium to prepare a negative electrode slurry. The negative electrode slurry was then coated on both sides of a negative electrode current collector made of 8 μm thick copper foil, and the coating was allowed to dry. The coating was then calendered using calendering rollers and cut to the specified electrode size to fabricate the negative electrode. At this point, as... Figure 2As shown, first and second negative current collector exposed portions are respectively provided on the surface of the negative current collector, and a nickel negative electrode tab is welded to the first negative current collector exposed portion. It should be noted that the negative electrode tab is joined within a range not exceeding the center of the negative electrode in the width direction, and is disposed with a gap axially separated from the positive electrode tab during the fabrication of the electrode body. Furthermore, as... Figure 2 As shown, at one end of the negative electrode 12 along its length, there is a contact portion that exposes the surface of the negative electrode current collector.

[0064] [Fabrication of Electrodes]

[0065] An electrode body is manufactured by winding the positive and negative electrodes into a spiral shape, with a 14μm thick polyethylene spacer sandwiched between them. At this time, a gap is formed between the positive electrode tab and the negative electrode tab in a range of more than 25% and less than 35% of the axial length of the electrode body from the lower end of the electrode body.

[0066] [Preparation of non-aqueous electrolytes]

[0067] A non-aqueous electrolyte was prepared by adding 5 parts by mass of vinylene carbonate (VC) to 100 parts by mass of a mixed solvent obtained by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7, and then dissolving lithium hexafluoride phosphate (LiPF6) at a concentration of 1.3 mol / L.

[0068] [Fabrication of Non-Aqueous Electrolyte Secondary Batteries]

[0069] Insulating plates are placed above and below the fabricated electrode body, which is then housed inside the outer packaging can. It should be noted that a metal can made of bottomed cylindrical steel with a diameter of φ21mm and a height of 70mm is used as the outer packaging can. The negative electrode tab is welded to the bottom of the outer packaging can, and the positive electrode tab is welded to the sealing body. Furthermore, the contact portion of the outer circumference of the electrode body 14 contacts the inner surface of the outer packaging can. Afterward, a non-aqueous electrolyte is injected into the outer packaging can, and the opening of the outer packaging can is sealed using the sealing body with a gasket in between, thus fabricating a non-aqueous electrolyte secondary battery.

[0070] <Comparative Example>

[0071] Except that the positive electrode tab is joined within a range not exceeding the central portion of the width direction of the positive electrode, and the negative electrode tab is joined within a range not exceeding the central portion of the width direction of the negative electrode, it is manufactured in the same manner as the non-aqueous electrolyte secondary battery of the embodiment. At this time, a gap between the positive electrode tab and the negative electrode tab is formed in a range that does not overlap with the axial central portion of the electrode body and is located at more than 45% and less than 55% of the axial length of the electrode body from the upper (lower) end of the electrode body.

[0072] [Collision Test]

[0073] The fabricated non-aqueous electrolyte secondary battery was charged to 50% SOC at a constant current of 0.3C at 25°C. Then, a T6 impact test was conducted according to UN transport test conditions. Specifically, a 15.8mm diameter metal rod was placed at the axial center of the non-aqueous electrolyte secondary battery, and a 9.1kg weight was dropped from a height of 70cm. Afterward, the non-aqueous electrolyte secondary battery was disassembled to check for damage to any electrodes; batteries without damage were deemed OK. Ten non-aqueous electrolyte secondary batteries from both the example and comparative examples were tested, and the number of OK batteries was used for evaluation. It should be noted that the specified drop height of the weight in the T6 impact test was 61cm.

[0074] As a result, all 10 out of 10 non-aqueous electrolyte secondary batteries in the embodiment were deemed OK, while only 6 out of 10 non-aqueous electrolyte secondary batteries in the comparative example were deemed OK. Based on this result, it can be said that by offsetting the gap between the positive and negative electrode tabs from the axial center of the electrode body, and by placing the positive or negative electrode tab at the axial center of the electrode body, the strength of the axial center side of the electrode body can be increased, and deformation of the battery's axial center side caused by externally applied loads can be suppressed.

[0075] The present invention can be further illustrated by the following embodiments.

[0076] Component 1:

[0077] A non-aqueous electrolyte secondary battery comprises an electrode body formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode along their length, separated by a spacer, and a bottomed cylindrical outer packaging can containing the electrode body. The positive electrode has a positive current collector exposed portion without a positive electrode binder layer, and the negative electrode has a negative current collector exposed portion without a negative electrode binder layer. A positive electrode tab protruding from one of the two ends of the electrode body is joined to the positive current collector exposed portion. The negative current collector… The exposed portion is joined with a negative electrode tab that protrudes from the other end of the two ends of the electrode body along the axial direction. The exposed portion of the negative current collector is provided in a region where at least a portion of it overlaps with the opposing region in the width direction of the negative electrode. The opposing region is the region of the negative electrode that is opposite to the exposed portion of the positive current collector separated by the spacer. When viewed radially from the electrode body, the positive electrode tab and the negative electrode tab are provided with a gap along the axial direction of the electrode body. The gap is positioned at a position that does not overlap with the central portion of the axial direction of the electrode body.

[0078] Composition 2:

[0079] According to the non-aqueous electrolyte secondary battery described in configuration 1, the gap is provided in a range of 20% or more and less than 50% of the axial length of the electrode body, starting from both ends of the electrode body in the axial direction.

[0080] Composition 3:

[0081] According to configuration 1 or 2, the area of ​​the positive electrode opposite to the exposed portion of the negative electrode current collector, separated by the spacer, is covered by an insulating member.

[0082] Composition 4:

[0083] According to any one of the non-aqueous electrolyte secondary batteries described in 1 to 3, the exposed portion of the positive electrode current collector is provided throughout the width direction of the positive electrode.

[0084] The exposed portion of the aforementioned negative current collector is provided throughout the width direction of the aforementioned negative electrode.

[0085] Component 5:

[0086] According to any one of the non-aqueous electrolyte secondary batteries described in 1 to 3, the exposed portion of the positive electrode current collector contacts only one of the two ends in the width direction of the positive electrode, and the exposed portion of the negative electrode current collector contacts only the other end in the width direction of the negative electrode.

[0087] Explanation of reference numerals in the attached figures

[0088] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 11A upper end, 11B lower end, 12 Negative electrode, 12A upper end, 12B lower end, 13 Spacer, 14 Electrode body, 16 Outer packaging can, 17 Sealing body, 18, 19 Insulating plate, 20 Positive electrode tab, 21 Negative electrode tab, 22 Slotted part, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating component, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive current collector, 31 Positive electrode flux layer, 32 Exposed part of positive current collector, 33 Exposed part of the first positive current collector, 35 Exposed part of the second positive current collector, 37 Exposed part of the third positive current collector, 40 Negative current collector, 41 Negative electrode flux layer, 42 Exposed part of the negative current collector, 43 Contact portion, 50 insulating components.

Claims

1. A non-aqueous electrolyte secondary battery, comprising an electrode body formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode along the length direction with a spacer between them, and a bottomed cylindrical outer packaging can containing the electrode body. The positive electrode has a positive electrode current collector exposed portion where no positive electrode binder layer is provided. The negative electrode has an exposed portion of the negative electrode current collector where no negative electrode binder layer is provided. A positive electrode tab protruding from one of the two ends of the electrode body along its axial direction is joined to the exposed portion of the positive current collector. A negative electrode tab protruding from one of the two ends of the electrode body along its axial direction is engaged at the exposed portion of the negative current collector. The exposed portion of the negative current collector is disposed in a region where at least a portion overlaps with the opposing region in the width direction of the negative electrode. The opposing region is the area of ​​the negative electrode that is opposite to the exposed portion of the positive current collector, separated by the spacer. Viewed radially from the electrode body, the positive electrode tab and the negative electrode tab are disposed with a gap spaced apart along the axial direction of the electrode body. The gap is positioned so as not to overlap with the axial center of the electrode body.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The gap is provided within a range of more than 20% and less than 50% of the axial length of the electrode body, starting from both ends of the electrode body along its axial direction.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The area of ​​the positive electrode that is opposite to the exposed portion of the negative electrode current collector, separated by the spacer, is covered by an insulating member.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The exposed portion of the positive current collector is provided throughout the width direction of the positive electrode. The exposed portion of the negative current collector is provided throughout the width direction of the negative electrode.

5. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The exposed portion of the positive current collector contacts only one of the two ends of the positive electrode in the width direction. The exposed portion of the negative current collector contacts only one of the two ends of the negative electrode in the width direction.

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