Secondary battery

Abstract

The utility model relates to a secondary battery. This secondary battery is provided with: a wound electrode body in which a positive electrode sheet in which a positive electrode active material layer is formed excluding a positive electrode collector foil exposed portion along one long side of a positive electrode collector foil, and a negative electrode sheet in which a negative electrode active material layer is formed are wound with a separator interposed therebetween; a negative electrode active material layer is formed on the negative electrode sheet except a negative electrode exposed part along one long side of the negative electrode current collector foil; a battery case accommodating the wound electrode body and an electrolyte; a positive electrode collector terminal electrically connected to a positive electrode collector foil portion formed by converging the positive electrode collector foil exposed portions; a negative electrode collector terminal electrically connected to a negative electrode collector foil portion formed by gathering the negative electrode collector foil exposed portions; and an insulating layer formed in at least one of a region of the exposed positive electrode collector foil portion other than the positive electrode collector foil portion and a region of the exposed negative electrode collector foil portion other than the negative electrode collector foil portion.

Description

Technical Field

[0001] The present utility model relates to a secondary battery. Background Art

[0002] In Japanese Unexamined Patent Application Publication No. 2023-089639, a secondary battery is disclosed that includes a wound electrode body formed by winding a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween. The positive electrode sheet extends beyond the separator on the first side in the winding axis direction, and a positive electrode current collector is joined to this portion. The outermost periphery of the negative electrode sheet is wound on the outer peripheral side with respect to the outermost periphery of the positive electrode sheet. The portion of the separator that is wound on the outer peripheral side with respect to the outermost periphery of the negative electrode sheet extends along the first side and ends at the portion where the positive electrode current collector is joined to the positive electrode sheet. Thereby, the situation where foreign matter enters the gap between the outermost positive electrode sheet and the negative electrode sheet is reduced. Summary of the Utility Model

[0003] In Japanese Unexamined Patent Application Publication No. 2023-089639, by elongating the outermost separator and joining the separator and the positive electrode sheet to the positive electrode current collector together, it is possible to prevent a short circuit at the gap between the outermost positive electrode sheet and the negative electrode sheet. However, in Japanese Unexamined Patent Application Publication No. 2023-089639, the impregnation property of the electrolyte into the wound electrode body is not considered, and the impregnation property of the electrolyte sometimes decreases.

[0004] The present utility model has been completed in view of such problems. An object of the present utility model is to provide a secondary battery that can prevent a short circuit at the gap between the positive electrode sheet and the negative electrode sheet with a separator interposed therebetween and suppress a decrease in the impregnation property of the electrolyte into the wound electrode body.

[0005] A secondary battery according to one aspect includes:

[0006] A wound electrode body formed by winding a positive electrode sheet and a negative electrode sheet with a strip-shaped separator interposed therebetween, wherein the positive electrode sheet is formed with a positive electrode active material layer except for a positive electrode current collector foil exposed portion along one long side of the strip-shaped positive electrode current collector foil, and the negative electrode sheet is formed with a negative electrode active material layer except for a negative electrode current collector foil exposed portion along one long side of the strip-shaped negative electrode current collector foil;

[0007] A battery case that houses the wound electrode body and the electrolyte;

[0008] A positive electrode current collecting terminal electrically connected to a positive electrode current collector foil portion formed by gathering the positive electrode current collector foil exposed portions;

[0009] A negative electrode current collecting terminal electrically connected to a negative electrode current collector foil portion formed by gathering the negative electrode current collector foil exposed portions; and

[0010] An insulating layer formed in at least any one of a region of the positive electrode current collector foil exposed portion other than the positive electrode current collector foil portion and a region of the negative electrode current collector foil exposed portion other than the negative electrode current collector foil portion.

[0011] According to the secondary battery of the above aspect, the insulating layer is formed at predetermined intervals along the longitudinal direction of the positive electrode current collecting foil or the negative electrode current collecting foil.

[0012] According to the secondary battery of the above aspect, the insulating layer is formed on both the region of the positive electrode current collector foil exposed portion excluding the positive electrode current collector foil portion and the region of the negative electrode current collector foil exposed portion excluding the negative electrode current collector foil portion.

[0013] According to the secondary battery described in the above embodiment, the separator includes a first separator and a second separator, and the first separator, the positive electrode sheet, the second separator and the negative electrode sheet are sequentially overlapped and aligned along the long side direction and wound around a winding axis set along the short side direction.

[0014] The secondary battery according to the above-described method is characterized in that the battery case is a square case having a substantially rectangular outer shape, the wound electrode body has a flat rectangular outer shape, at one end in the direction of the winding axis, the exposed portion of the positive electrode collector foil is arranged to protrude from the negative electrode sheet and is stacked, and at the other end in the direction of the winding axis, the exposed portion of the negative electrode collector foil is arranged to protrude from the positive electrode sheet and is stacked, and the wound electrode body is housed in the battery case in such a manner that the winding axis extends in the width direction of the battery case.

[0015] According to the present invention, a short circuit can be prevented at the gap between the positive electrode sheet and the negative electrode sheet via the separator, and a decrease in the permeability of the electrolyte solution to the wound electrode body can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like symbols represent like elements, and wherein:

[0017] Figure 1 It is a diagram showing the external appearance of a secondary battery according to an embodiment.

[0018] Figure 2 It is an explanation Figure 1 Diagram of the internal structure of a secondary battery.

[0019] Figure 3 It is an exploded view illustrating the structure of a wound electrode body.

[0020] Figure 4 This is a diagram of a wound electrode body viewed from the side.

[0021] Figure 5 It will Figure 4 FIG1 is an enlarged view of a portion of the cross section of the wound electrode body taken along the cutting line V.

[0022] Figure 6 It is a view obtained by magnifying a part of the cross-section of the wound electrode body in the cut line VI of Figure 4 . DETAILED DESCRIPTION

[0023] Hereinafter, this embodiment will be described with reference to the drawings. In addition, the following embodiments are not intended to limit the technology disclosed herein. For the sake of clarity, the following description and drawings are appropriately omitted and simplified. The dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships. In addition, in each drawing, the same reference numerals are attached to the same elements, and repeated descriptions are omitted as needed.

[0024] The embodiment relates to, for example, a secondary battery used as a driving power source for a battery electric vehicle or the like. In this specification, a "secondary battery" refers to a general electrical storage device capable of repeated charge and discharge, including electrical storage elements such as so-called storage batteries and electric double layer capacitors. Here, a flat square lithium ion secondary battery will be described in detail as an example. A "lithium secondary battery" is a secondary battery that uses lithium ions as charge carriers and realizes charge and discharge through the movement of charges accompanied by lithium ions between the positive and negative electrodes.

[0025] Figure 1 It is a view showing the outer shape of the secondary battery 10 of the embodiment. Figure 2 It is a view for explaining Figure 1 the internal structure of the secondary battery 10. As shown in Figure 1 , 2 , the secondary battery 10 has a structure in which a wound electrode body 20 and an electrolytic solution (not shown) are housed in a battery case 11. W in the figure represents the width direction of the battery case 11. H in the figure represents the height direction of the battery case 11. In addition, the direction orthogonal to the width direction W and the height direction H is defined as the thickness direction D of the battery case 11. In addition, these directions do not limit the installation method of the secondary battery 10.

[0026] The battery case 11 is a square container having an outer shape of a substantially rectangular parallelepiped with an internal space. As the battery case 11, for example, a light and highly thermally conductive metal material such as aluminum or stainless steel (SUS) is used. The battery case 11 includes a main body 12 having an opening portion opening upward and a lid body 13 closing the opening portion. The main body 12 has a bottom surface having a substantially rectangular shape, a pair of wide surfaces, and a narrow surface disposed between the pair of wide surfaces. In Figure 1 , the pair of wide surfaces extend upward from the front end and the rear end of the bottom surface, respectively. In addition, the pair of narrow surfaces extend upward from the left end and the right end of the bottom surface, respectively. The edge of the opening portion of the main body 12 and the outer edge of the lid body 13 are laser welded to seal the battery case 11.

[0027] The lid 13 of the battery case 11 is provided with a positive external terminal 14 and a negative external terminal 15. In addition, the lid 13 is provided with a liquid injection port (not shown) for injecting electrolyte. The liquid injection port can be provided, for example, between the positive external terminal 14 and the negative external terminal 15 of the lid 13. As Figure 2 shown, a part of the positive external terminal 14 and the negative external terminal 15 are respectively connected to the positive current collecting terminal 16 and the negative current collecting terminal 17 inside the battery case 11.

[0028] The wound electrode body 20 is housed in a space surrounded by the main body 12 and the lid 13. Figure 3 is an exploded view illustrating the structure of the wound electrode body 20. Figure 4 is a view when observing the wound electrode body 20 from the side. In Figure 4 it shows the side surface of the wound electrode body 20 on the side connected to the positive current collecting terminal 16, indicated by the dashed line of Figure 3 .

[0029] As Figure 3 shown, the wound electrode body 20 includes a strip-shaped first separator 1, a second separator 2, a positive electrode sheet 3, and a negative electrode sheet 4. The length direction of the first separator 1, the second separator 2, the positive electrode sheet 3, and the negative electrode sheet 4 is set as the long side direction, and the width direction is set as the short side direction. The first separator 1, the positive electrode sheet 3, the second separator 2, and the negative electrode sheet 4 are sequentially overlapped and aligned in the long side direction and wound around the winding axis X. In the present embodiment, the direction of the winding axis X of the wound electrode body 20 coincides with the width direction W of the secondary battery 10. As Figure 4 shown, the cross section of the wound electrode body 20 is an elliptical shape.

[0030] The positive electrode sheet 3 includes a positive current collecting foil 30 and a positive electrode active material layer 31. The positive current collecting foil 30 is a supporting member for the positive electrode active material layer 31 and is a conductive member for extracting charges from the positive electrode active material layer 31. In a region along one long side of the strip-shaped positive current collecting foil 30, a positive current collecting foil exposed portion 32 is provided. The positive electrode active material layer 31 is formed in a region of the positive current collecting foil 30 other than the positive current collecting foil exposed portion 32. The positive electrode active material layer 31 is formed in a strip shape along the other long side of the positive current collecting foil 30. The positive electrode active material layer 31 can be formed on one side or both sides of the positive current collecting foil 30. Here, the positive electrode active material layer 31 is formed on both sides of the positive current collecting foil 30. That is, the positive electrode sheet 3 is in a long strip shape and is arranged such that the wide positive electrode active material layer 31 and the narrow positive current collecting foil exposed portion 32 are arranged in the width direction.

[0031] In addition, although not shown in Figure 3 , the negative electrode sheet 4 includes a negative current collecting foil 40 and a negative electrode active material layer 41 (refer toFigure 5 )。The negative current collector foil 40 is a supporting member for the negative active material layer 41 and is a conductive member for extracting electric charges from the negative active material layer 41. In a region along one long side of the strip-shaped negative current collector foil 40, a negative current collector foil exposed portion is provided. The negative active material layer 41 is formed in a region of the negative current collector foil 40 other than the negative current collector foil exposed portion. The negative active material layer 41 is formed in a strip shape along the other long side of the negative current collector foil 40. The negative active material layer 41 may be formed on one or both sides of the negative current collector foil 40. Here, the negative active material layer 41 is formed on both sides of the negative current collector foil 40. That is, the negative electrode sheet 4 is long and is arranged in such a manner that the wide negative active material layer 41 and the narrow negative current collector foil exposed portion are arranged in the width direction.

[0032] As the members and materials constituting the secondary battery 10, the same members and materials as those used in widely known lithium ion secondary batteries are used, and they are not particularly limited. An example of the members and materials constituting the secondary battery 10 is shown below.

[0033] As the positive current collector foil 30 constituting the positive electrode sheet 3, for example, aluminum (including aluminum alloy) foil or the like can be cited. As examples of the positive active material contained in the positive active material layer 31, lithium transition metal oxides (for example, LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, etc.), lithium transition metal phosphorus oxides (for example, LiFePO4, etc.), etc. The positive active material layer 31 may contain components other than the active material, such as a conductive material, a binder, etc. As the conductive material, for example, carbon black such as acetylene black (AB) or other carbon materials (for example, graphite, etc.) can be used. As the binder, for example, polyvinylidene fluoride (PVdF) or the like can be used.

[0034] As the negative current collector foil 40 constituting the negative electrode sheet 4, for example, copper foil or the like can be cited. As the negative active material contained in the negative active material layer 41, for example, carbon materials such as graphite, hard carbon, and soft carbon can be used. When graphite is used as the negative active material, the negative active material can be natural graphite, artificial graphite, or can be coated with an amorphous carbon material. The negative active material layer 41 may contain components other than the active material, such as a binder, a thickener, etc. As the binder, for example, styrene-butadiene rubber (SBR) or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like can be used.

[0035] The first separator 1 and the second separator 2 insulate the positive electrode plate 3 from the negative electrode plate 4 and provide a movement path for charge carriers between the positive electrode active material layer 31 and the negative electrode active material layer 41. As the first separator 1 and the second separator 2, porous sheets (films) made of polyolefins such as polyethylene (PE) and polypropylene (PP) can be used. Such porous sheets can be either a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat-resistant layer (HRL) can also be provided on the surfaces of the first separator 1 and the second separator 2.

[0036] The electrolytic solution typically includes a non-aqueous solvent and a supporting salt. As the non-aqueous solvent, known solvents used as non-aqueous solvents for electrolytic solutions of lithium-ion secondary batteries can be used. For example, as the non-aqueous solvent, carbonates, ethers, esters, nitriles, sulfones, lactones, etc. can be cited. Examples of carbonates include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. Such non-aqueous solvents can be used alone or in combination of two or more.

[0037] As the supporting salt, for example, lithium salts such as LiPF6, LiBF4, LiClO4, etc. (preferably LiPF6) are appropriately used. The electrolytic solution can also contain other components. Examples of other components include gas generators such as biphenyl (BP) and cyclohexylbenzene (CHB), film-forming agents, dispersants, thickeners, etc.

[0038] At the central portion in the winding axis X direction of the wound electrode body 20, the positive electrode active material layer 31 and the negative electrode active material layer 41 are laminated to form a core portion where charge and discharge reactions occur. In addition, in the wound electrode body 20, at one end in the winding axis X direction ( Figure 3 the left end), there is a positive electrode current collector foil laminated portion 33, which is laminated in a state where the positive electrode current collector foil exposed portion 32 protrudes from the negative electrode plate 4. In addition, in the wound electrode body 20, at the other end in the winding axis X direction (not shown, which is Figure 3 the right end), there is a negative electrode current collector foil laminated portion, which is laminated in a state where the negative electrode current collector foil exposed portion protrudes from the positive electrode plate 3.

[0039] As Figure 4 shown, the positive electrode current collector foil exposed portion 32 (hereinafter referred to as "collector foil") converges at the central portion in the height direction H of the positive electrode current collector foil laminated portion 33 to form a positive electrode collector foil portion 34. Figure 5 is a diagram obtained by magnifying a part of the cross-section of the wound electrode body at the cut line V of Figure 4 . At Figure 5In [the figure], the vicinity of the positive electrode current collector foil portion 34 at the cut line V as viewed from the upper side (hollow arrow side) is shown. As Figure 4 shown, the positive electrode current collector terminal 16 is electrically connected to the positive electrode current collector foil portion 34 by ultrasonic welding or the like. As Figure 5 shown, in the positive electrode current collector foil portion 34, adjacent positive electrode current collector foils 30 are collected, so foreign matter does not intrude between the positive electrode sheet 3 and the negative electrode sheet 4.

[0040] Similarly, in the central portion in the height direction H of the negative electrode current collector foil laminated portion, a negative electrode current collector foil exposed portion is collected to form a negative electrode current collector foil portion. The negative electrode current collector terminal 17 is electrically connected to the negative electrode current collector foil portion. In the negative electrode current collector foil portion, adjacent negative electrode current collector foils are collected, so foreign matter does not intrude between the positive electrode sheet 3 and the negative electrode sheet 4.

[0041] An insulating layer 35 is formed in at least any one of the region of the positive electrode current collector foil exposed portion 32 other than the positive electrode current collector foil portion 34 and the region of the negative electrode current collector foil exposed portion other than the negative electrode current collector foil portion. The insulating layer 35 is preferably formed in both the region of the positive electrode current collector foil exposed portion 32 other than the positive electrode current collector foil portion 34 and the region of the negative electrode current collector foil exposed portion other than the negative electrode current collector foil portion.

[0042] Hereinafter, the insulating layer 35 formed in the positive electrode current collector foil exposed portion 32 will be described in detail. In addition, in the negative electrode current collector foil exposed portion, an insulating layer 35 is also formed in the same manner as the positive electrode current collector foil exposed portion 32, so the description thereof is omitted. The insulating layer 35 is, for example, a cured body of a liquid insulating paste. The insulating paste may contain, for example, an inorganic substance having insulating properties, a solvent for the insulating paste, and a resin component. The inorganic substance may be at least 1 of powdered alumina, boehmite, and titanium dioxide. The solvent for the insulating paste uses an NMP solution as an example of an organic solvent. The resin component functions as an adhesive in the insulating layer 35. The resin component may be at least 1 selected from the group including PVDF, PVA, and propylene, which are polymer materials soluble in NMP. The insulating layer 35 preferably has flexibility when the positive electrode current collector foil exposed portion 32 is collected.

[0043] As Figure 3 shown, the insulating layer 35 is formed at a predetermined interval along the long side direction of the positive electrode current collector foil exposed portion 32. The "predetermined interval" for forming the insulating layer 35 is preferably a pitch at which the insulating layer 35 is formed over the entire region of the positive electrode current collector foil exposed portion 32 other than the positive electrode current collector foil portion 34 when the positive electrode sheet 3 is wound. In addition, the insulating layer 35 is formed on both sides of the positive electrode current collector foil exposed portion 32. Thus, when the positive electrode sheet 3 is wound to form the wound electrode body 20, the positive electrode current collector foil 30 is exposed only at the positive electrode current collector foil portion 34.

[0044] Figure 6 is to Figure 4An enlarged view of a part of the cross-section of the wound electrode body in cutting line VI. In Figure 6 , the vicinity of the positive current collector foil laminated portion 33 at cutting line VI as viewed from the upper side (the side of the hollow arrow) is shown. As Figure 6 shown, in the positive current collector foil laminated portion 33, insulating layers 35 are formed on both surfaces of the positive current collector foil exposed portion 32.

[0045] Generally, it is known that metal foreign matters such as welding spatter are generated during battery manufacturing and invade the inside of the secondary battery 10 through the liquid injection port. The metal foreign matters invading the inside of the secondary battery 10 may cause conduction between the battery case 11 and the wound electrode body 20 or between the positive and negative electrodes in the wound electrode body 20, resulting in a short circuit.

[0046] Usually, during electrolyte infiltration, the electrolyte infiltrates from the regions of the positive current collector foil laminated portion 33 above and below the positive current collector foil portion 34 toward the center of the wound electrode body 20. Considering the case where a metal foreign matter invading the inside of the secondary battery 10 through the liquid injection port short-circuits between the positive and negative electrodes in the wound electrode body 20, the path along which the metal foreign matter moves along with the flow of the electrolyte infiltrating into the wound electrode body 20. As a means of preventing a short circuit based on this path, preventing metal foreign matters from invading between the positive and negative electrodes can be cited.

[0047] In Japanese Unexamined Patent Application Publication No. 2023-089639, the outermost diaphragm is elongated and the diaphragm is joined to the positive current collector together with the positive electrode sheet, thereby suppressing the invasion of metal foreign matters. However, since it is covered with the diaphragm, the infiltration property of the electrolyte may decrease.

[0048] In contrast, in the embodiment, in the positive current collector foil exposed portion 32, insulating layers 35 are formed in regions other than the positive current collector foil portion 34. Therefore, when injecting the electrolyte, even if a metal foreign matter F enters the gap between the positive electrode sheet 3 and the negative electrode sheet 4 of the wound electrode body 20, the generation of a short circuit can be suppressed. In addition, as Figure 6 shown, in the positive current collector foil laminated portion 33, the positive electrode sheet 3 is not joined to the diaphragm as in Japanese Unexamined Patent Application Publication No. 2023-089639, so gaps are generated in the positive current collector foil laminated portion 33 other than the positive current collector foil portion 34 during current collection. Therefore, the electrolyte can infiltrate into the wound electrode body 20 without changing the liquid injection conditions of the electrolyte.

[0049] In addition, the present utility model is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist.

Claims

1. A secondary battery, characterized in that Comprising: A wound electrode body formed by winding a positive electrode sheet and a negative electrode sheet with a strip-shaped separator interposed therebetween. The positive electrode sheet has a positive electrode active material layer formed thereon except for a positive electrode current collector foil exposed portion along one long side of the strip-shaped positive electrode current collector foil. The negative electrode sheet has a negative electrode active material layer formed thereon except for a negative electrode current collector foil exposed portion along one long side of the strip-shaped negative electrode current collector foil. A battery case for housing the wound electrode body and an electrolytic solution. A positive electrode current collector terminal electrically connected to a positive electrode current collector foil portion formed by gathering the positive electrode current collector foil exposed portions. A negative electrode current collector terminal electrically connected to a negative electrode current collector foil portion formed by gathering the negative electrode current collector foil exposed portions; and An insulating layer formed in at least any one of a region of the positive electrode current collector foil exposed portion other than the positive electrode current collector foil portion and a region of the negative electrode current collector foil exposed portion other than the negative electrode current collector foil portion.

2. The secondary battery according to claim 1, wherein the insulating layer is formed at a predetermined interval along the long side direction of the positive electrode current collector foil or the negative electrode current collector foil.

3. The secondary battery according to claim 1, wherein the insulating layer is formed in both a region of the positive electrode current collector foil exposed portion other than the positive electrode current collector foil portion and a region of the negative electrode current collector foil exposed portion other than the negative electrode current collector foil portion.

4. The secondary battery according to claim 1, wherein the separator includes a first separator and a second separator, and the first separator, the positive electrode sheet, the second separator, and the negative electrode sheet are sequentially overlapped and wound around a winding axis set along the short side direction in alignment with each other along the long side direction.

5. The secondary battery according to claim 4, wherein the battery case is a square case having a substantially rectangular parallelepiped outer shape, the wound electrode body has a flat rectangular parallelepiped outer shape, at one end in the winding axis direction, the positive electrode current collector foil exposed portion is laminated so as to protrude from the negative electrode sheet, at the other end in the winding axis direction, the negative electrode current collector foil exposed portion is laminated so as to protrude from the positive electrode sheet, and the wound electrode body is housed in the battery case such that the winding axis direction extends in the width direction of the battery case.

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