Secondary battery

Abstract

To provide a secondary battery in which a short circuit in a gap between a cathode plate and an anode with a separator interposed therebetween can be prevented and a decrease in impregnation properties of an electrolytic solution into a wound electrode body can be suppressed.SOLUTION: A secondary battery according to an embodiment includes: a wound electrode body in which a cathode plate where a cathode active material layer is formed except for cathode current collector foil exposed portions extending along one long side of a band-shaped cathode current collector foil and an anode plate where an anode active material layer 41 is formed except for anode current collector foil exposed portions extending along one long side of a band-shaped anode current collector foil are wound around via a band-shaped separator; a battery case that houses the wound electrode body and an electrolytic solution; a cathode current collector terminal that is electrically connected to a cathode current collector foil portion where the cathode current collector foil exposed portions are collected; an anode current collector terminal electrically connected to an anode current collector foil portion where the anode current collector foil exposed portions are collected; and insulating layers formed in at least one of a region of the cathode current collector foil exposed portions except for the cathode current collector foil portion and a region of the anode current collector foil exposed portions except for the anode current collector foil portion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Patent Document 1 discloses a secondary battery including a wound electrode body in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween. The positive electrode plate protrudes from the separator on a 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 plate is wound on the outermost periphery side of the positive electrode plate. The portion of the separator wound on the outermost periphery side of the negative electrode plate extends to the first side and is stopped at the portion where the positive electrode current collector and the positive electrode plate are joined. This reduces the intrusion of foreign matter into the gap between the outermost positive electrode plate and the negative electrode plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-089639 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the outermost separator is stretched and the separator is joined to the positive electrode current collector together with the positive electrode plate, thereby preventing a short circuit in the gap between the outermost positive electrode plate and the negative electrode plate. However, Patent Document 1 does not take into consideration the impregnation of the wound electrode body when injecting the electrolyte, and there is a risk that the impregnation of the electrolyte may decrease.

[0005] The present invention has been made in consideration of such problems, and an object of the present invention is to provide a secondary battery that can prevent a short circuit in the gap between a positive electrode plate and a negative electrode plate with a separator interposed therebetween and suppress a decrease in the impregnation of the electrolyte into the wound electrode body. [Means for solving the problem]

[0006] A secondary battery according to one embodiment includes a wound electrode body formed by winding a positive electrode plate on which a positive electrode active material layer is formed except for a positive electrode current collector foil exposed portion along one long side of a band-shaped positive electrode current collector foil, and a negative electrode plate on which a negative electrode active material layer 41 is formed except for a negative electrode exposed portion along one long side of a band-shaped negative electrode current collector foil, with a band-shaped separator interposed therebetween, a battery case that contains the wound electrode body and an electrolyte, a positive electrode current collector terminal electrically connected to a positive electrode current collector portion that gathers together the positive electrode current collector foil exposed portions, a negative electrode current collector terminal electrically connected to a negative electrode current collector portion that gathers together the negative electrode current collector foil exposed portions, and an insulating layer formed on at least one of a region of the positive electrode current collector foil exposed portion excluding the positive electrode current collector portion and a region of the negative electrode current collector foil exposed portion excluding the negative electrode foil portion. Effect of the Invention

[0007] According to the present invention, it is possible to prevent a short circuit in the gap between the positive electrode plate and the negative electrode plate with the separator interposed therebetween, and to suppress a decrease in the impregnation of the electrolyte into the wound electrode body. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing the external shape of a secondary battery according to an embodiment; [Diagram 2] 2 is a diagram illustrating an internal configuration of the secondary battery of FIG. 1. [Diagram 3] FIG. 2 is an exploded view illustrating the configuration of a wound electrode body. [Figure 4] FIG. 4 is a side view of the wound electrode body. [Diagram 5] 5 is an enlarged view of a portion of the cross section of the wound electrode body taken along line V in FIG. [Figure 6] 6 is an enlarged view of a portion of the cross section of the wound electrode body taken along line VI in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is not intended to limit the technology disclosed herein. For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. The dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships. In addition, in each drawing, the same elements are given the same reference numerals, and repeated explanations are omitted as necessary.

[0010] The embodiments relate to a secondary battery used as a driving power source for electric vehicles and the like. In this specification, the term "secondary battery" refers to a general storage device that can be repeatedly charged and discharged, and includes storage elements such as so-called storage batteries and electric double layer capacitors. Here, the embodiments will be described in detail using a flat rectangular lithium ion secondary battery as an example. The term "lithium secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and realizes charging and discharging by the transfer of charge associated with the lithium ions between the positive and negative electrodes.

[0011] FIG. 1 is a diagram showing the external shape of a secondary battery 10 according to an embodiment. FIG. 2 is a diagram illustrating the internal configuration of the secondary battery 10 of FIG. 1. As shown in FIGS. 1 and 2, the secondary battery 10 has a structure in which a wound electrode body 20 and an electrolyte (not shown) are accommodated in a battery case 11. W in the diagram indicates the width direction of the battery case 11. H in the diagram indicates the height direction of the battery case 11. The direction perpendicular to the width direction W and the height direction H is defined as the thickness direction D of the battery case 11. Note that these directions do not limit the installation mode of the secondary battery 10.

[0012] The battery case 11 is a square container having an internal space and an outer shape of a substantially rectangular parallelepiped. For example, a lightweight metal material with good thermal conductivity, such as aluminum or stainless steel (SUS), is used for the battery case 11. The battery case 11 includes a main body 12 having an opening that opens upward, and a lid 13 that closes the opening. The main body 12 has a substantially rectangular bottom surface, a pair of wide surfaces, and a narrow surface disposed between the pair of wide surfaces. In FIG. 1, the pair of wide surfaces extend upward from the front end and rear end of the bottom surface, respectively. The pair of narrow surfaces also extend upward from the left end and right end of the bottom surface, respectively. The periphery of the opening of the main body 12 and the outer edge of the lid 13 are laser welded to seal the battery case 11.

[0013] The lid 13 of the battery case 11 is provided with a positive electrode external terminal 14 and a negative electrode external terminal 15. The lid 13 is also provided with a liquid injection port (not shown) for injecting an electrolyte. The liquid injection port may be provided, for example, between the positive electrode external terminal 14 and the negative electrode external terminal 15 of the lid 13. As shown in FIG. 2, parts of the positive electrode external terminal 14 and the negative electrode external terminal 15 are connected to a positive electrode current collector terminal 16 and a negative electrode current collector terminal 17, respectively, inside the battery case 11.

[0014] The wound electrode body 20 is housed in a space surrounded by the main body 12 and the lid body 13. Fig. 3 is an exploded view illustrating the configuration of the wound electrode body 20. Fig. 4 is a side view of the wound electrode body 20. Fig. 4 shows the side of the wound electrode body 20 to which the positive electrode collector terminal 16, indicated by the dashed line in Fig. 3, is connected.

[0015] As shown in FIG. 3, the wound electrode body 20 includes a strip-shaped first separator 1, a second separator 2, a positive electrode plate 3, and a negative electrode plate 4. The length direction of the first separator 1, the second separator 2, the positive electrode plate 3, and the negative electrode plate 4 is the long side direction, and the width direction is the short side direction. The first separator 1, the positive electrode plate 3, the second separator 2, and the negative electrode plate 4 are stacked in order with their long side directions aligned, and wound around a winding axis X. In this 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 shown in FIG. 4, the cross section of the wound electrode body 20 has an oval shape.

[0016] The positive electrode plate 3 includes a positive electrode current collector foil 30 and a positive electrode active material layer 31. The positive electrode current collector foil 30 is a support member for the positive electrode active material layer 31 and is a conductive member for extracting electric charge from the positive electrode active material layer 31. A positive electrode current collector foil exposed portion 32 is provided in a region along one long side of the band-shaped positive electrode current collector foil 30. The positive electrode active material layer 31 is formed in a region on the positive electrode current collector foil 30 excluding the positive electrode current collector foil exposed portion 32. The positive electrode active material layer 31 is formed in a band shape along the other long side of the positive electrode current collector foil 30. The positive electrode active material layer 31 can be formed on one side or both sides of the positive electrode current collector foil 30. Here, the positive electrode active material layer 31 is formed on both sides of the positive electrode current collector foil 30. That is, the positive electrode plate 3 is long, and is provided so that the wide positive electrode active material layer 31 and the narrow positive electrode current collector foil exposed portion 32 are aligned in the width direction.

[0017] Although not shown in FIG. 3, the negative electrode plate 4 includes a negative electrode current collector foil 40 and a negative electrode active material layer 41 (see FIG. 5). The negative electrode current collector foil 40 is a support member for the negative electrode active material layer 41 and is a conductive member for extracting electric charge from the negative electrode active material layer 41. A negative electrode current collector foil exposed portion is provided in a region along one long side of the band-shaped negative electrode current collector foil 40. The negative electrode active material layer 41 is formed in a region on the negative electrode current collector foil 40 excluding the negative electrode current collector foil exposed portion. The negative electrode active material layer 41 is formed in a band shape along the other long side of the negative electrode current collector foil 40. The negative electrode active material layer 41 can be formed on one side or both sides of the negative electrode current collector foil 40. Here, it is assumed that the negative electrode active material layer 41 is formed on both sides of the negative electrode current collector foil 40. That is, the negative electrode plate 4 is long, and is provided so that the wide negative electrode active material layer 41 and the narrow negative electrode current collector foil exposed portion are aligned in the width direction.

[0018] The components and materials constituting the secondary battery 10 are not particularly limited and may be the same as those used in widely known lithium ion secondary batteries. Examples of the components and materials constituting the secondary battery 10 are shown below.

[0019] The positive electrode current collector foil 30 constituting the positive electrode plate 3 is, for example, an aluminum (including aluminum alloy) foil. Examples of the positive electrode active material contained in the positive electrode active material layer 31 include lithium transition metal oxides (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , LiNiO 2 , LiCoO 2 , LiFeO 2 , LiMn 2 O 4 , LiNi 0.5 Mn 1.5 O 4 etc.), lithium transition metal phosphate compounds (e.g., LiFePO 4 The positive electrode active material layer 31 may include components other than the active material, such as a conductive material and a binder. As the conductive material, for example, carbon black such as acetylene black (AB) or other carbon materials (e.g., graphite) may be used. As the binder, for example, polyvinylidene fluoride (PVdF) may be used.

[0020] The negative electrode current collector foil 40 constituting the negative electrode plate 4 may be, for example, a copper foil. The negative electrode active material contained in the negative electrode active material layer 41 may be, for example, a carbon material such as graphite, hard carbon, or soft carbon. When graphite is used as the negative electrode active material, the negative electrode active material may be natural graphite or artificial graphite, and may be coated with an amorphous carbon material. The negative electrode active material layer 41 may contain components other than the active material, such as a binder or a thickener. As the binder, for example, styrene butadiene rubber (SBR) or the like may be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like may be used.

[0021] The first separator 1 and the second separator 2 insulate the positive electrode plate 3 and the negative electrode plate 4 from each other, and provide a path for charge carrier movement 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, a porous sheet (film) made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. Such a porous sheet may have 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) may be provided on the surface of the first separator 1 and the second separator 2.

[0022] The electrolyte typically contains a non-aqueous solvent and a supporting salt. As the non-aqueous solvent, a known solvent used as a non-aqueous solvent for an electrolyte for a lithium ion secondary battery can be used. For example, the non-aqueous solvent may be carbonates, ethers, esters, nitriles, sulfones, lactones, etc. 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 may be used alone or in combination of two or more.

[0023] The supporting salt is, for example, LiPF 6 , LiBF 4 , LiClO 4 Lithium salts such as (preferably LiPF 6 ) is preferably used. The electrolyte may contain other components. Examples of the other components include gas generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB), film forming agents, dispersants, thickeners, etc.

[0024] In the center of the wound electrode body 20 in the direction of the winding axis X, a positive electrode active material layer 31 and a negative electrode active material layer 41 are laminated to form a core portion where charge / discharge reactions take place. In addition, in the wound electrode body 20, at one end in the direction of the winding axis X (the left end in FIG. 3), there is a positive electrode current collector foil laminated portion 33 in which 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 direction of the winding axis X (the right end in FIG. 3, although not shown), there is a negative electrode current collector foil laminated portion in which the negative electrode current collector foil exposed portion protrudes from the positive electrode plate 3.

[0025] As shown in FIG. 4, the positive current collector foil exposed parts 32 are gathered together (hereinafter referred to as "collecting foil") at the center of the height direction H of the positive current collector foil laminated part 33 to form a positive current collector part 34. FIG. 5 is an enlarged view of a part of the cross section of the wound electrode body at the cutting line V in FIG. 4. FIG. 5 shows the vicinity of the positive current collector part 34 at the cutting line V as viewed from above (the side indicated by the outline arrow). As shown in FIG. 4, the positive current collector terminal 16 is electrically connected to the positive current collector part 34 by ultrasonic welding or the like. As shown in FIG. 5, the positive current collector part 34 collects the adjacent positive current collector foils 30, so that no foreign matter enters between the positive plate 3 and the negative plate 4.

[0026] Similarly, at the center of the height direction H of the negative current collector foil laminate, the exposed negative current collector foil portions are gathered together to form a negative current collector portion. A negative current collector terminal 17 is electrically connected to the negative current collector portion. Since adjacent negative current collector foils are collected in the negative current collector portion, no foreign matter can enter between the positive electrode plate 3 and the negative electrode plate 4.

[0027] An insulating layer 35 is formed on at least one of the region of the positive current collector foil exposed portion 32 excluding the positive electrode foil collecting portion 34 and the region of the negative current collector foil exposed portion excluding the negative electrode foil collecting portion. It is desirable that the insulating layer 35 is formed on both the region of the positive current collector foil exposed portion 32 excluding the positive electrode foil collecting portion 34 and the region of the negative current collector foil exposed portion excluding the negative electrode foil collecting portion.

[0028] The insulating layer 35 formed on the positive current collector foil exposed portion 32 will be described in detail below. The insulating layer 35 is also formed on the negative current collector foil exposed portion 32 in the same manner as the positive current collector foil exposed portion 32, and therefore will not be described. The insulating layer 35 is, for example, a hardened body of a liquid insulating paste. The insulating paste may include, 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 one of powdered alumina, boehmite, and titania. The solvent for the insulating paste is an NMP solution, which is an example of an organic solvent. The resin component functions as a binder in the insulating layer 35. The resin component may be at least one selected from the group consisting of PVDF, PVA, and acrylic, which are polymeric materials soluble in NMP. The insulating layer 35 preferably has flexibility when collecting the positive current collector foil exposed portion 32.

[0029] 3, the insulating layers 35 are formed at predetermined intervals along the long side direction of the positive current collector foil exposed portion 32. The "predetermined intervals" at which the insulating layers 35 are formed are preferably a pitch at which the insulating layers 35 are formed over the entire area of ​​the positive current collector foil exposed portion 32 excluding the positive current collector portion 34 when the positive current collector foil exposed portion 32 is wound. The insulating layers 35 are formed on both sides of the positive current collector foil exposed portion 32. As a result, when the positive current collector foil 3 is wound to form the wound electrode body 20, the positive current collector foil 30 is exposed only at the positive current collector portion 34.

[0030] Fig. 6 is an enlarged view of a portion of the cross section of the wound electrode body taken along cutting line VI in Fig. 4. Fig. 6 shows the vicinity of the positive current collector foil laminated portion 33 at cutting line VI as viewed from above (the side indicated by the outline arrow). As shown in Fig. 6, in the positive current collector foil laminated portion 33, insulating layers 35 are formed on both sides of the positive current collector foil exposed portion 32.

[0031] It is generally known that metal foreign matter such as welding spatters is generated during battery manufacturing and can infiltrate into the secondary battery 10 through the electrolyte filling port. Metal foreign matter that has infiltrated into the secondary battery 10 can cause electrical 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.

[0032] Typically, during impregnation with the electrolyte, the electrolyte permeates from the regions of the positive current collector foil laminated parts 33 above and below the positive electrode collector foil part 34 to the center of the wound electrode body 20. When a metallic foreign object that has entered the interior of the secondary battery 10 via the electrolyte inlet shorts out the positive and negative electrodes in the wound electrode body 20, one possible route is for the metallic foreign object to move along with the flow of the electrolyte that permeates the wound electrode body 20. One means for preventing a short circuit due to this route is to prevent the metallic foreign object from entering between the positive and negative electrodes.

[0033] In Patent Document 1, the outermost separator is extended and joined to the positive electrode current collector together with the positive electrode plate to prevent the intrusion of metallic foreign matter. However, being covered with the separator may reduce the impregnation of the electrolyte.

[0034] In contrast, in the embodiment, an insulating layer 35 is formed in the positive current collector exposed portion 32 in an area other than the positive current collector portion 34. Therefore, even if a metal foreign object F enters the gap between the positive electrode plate 3 and the negative electrode plate 4 of the wound electrode body 20 when the electrolyte is poured, the occurrence of a short circuit can be suppressed. In addition, as shown in FIG. 6, in the positive current collector laminated portion 33, the positive electrode plate 3 and the separator are not joined as in Patent Document 1, so that a gap is formed in the positive current collector laminated portion 33 other than the positive current collector portion 34 when the foils are collected. Therefore, it is possible to impregnate the wound electrode body 20 with the electrolyte without changing the electrolyte pouring conditions.

[0035] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0036] 1 First separator 2 Second separator 3 Positive plate 4 Negative plate 10 Secondary battery 11 Battery case 12 Main unit 13 Lid 14 Positive external terminal 15 Negative external terminal 16 Positive collector terminal 17 Negative current collector terminal 20 Wound electrode body 30 Positive electrode current collector foil 31 Positive electrode active material layer 32 Positive electrode current collector foil exposed part 33 Positive electrode current collector foil laminate 34 Positive electrode foil collection section 35 Insulating layer 40 Negative electrode current collector foil 41 Negative electrode active material layer X Winding axis

Claims

1. a positive electrode plate on which a positive electrode active material layer is formed except for an exposed portion of the positive electrode current collector foil along one long side of the band-shaped positive electrode current collector foil, and a negative electrode plate on which a negative electrode active material layer 41 is formed except for an exposed portion of the negative electrode current collector foil along one long side of the band-shaped negative electrode current collector foil, wound with a band-shaped separator interposed therebetween; a battery case that contains the wound electrode body and an electrolyte; a positive electrode current collecting terminal electrically connected to a positive electrode current collecting portion that gathers together the exposed portions of the positive electrode current collecting foil; a negative electrode current collecting terminal electrically connected to a negative electrode foil collecting portion that gathers together the exposed portions of the negative electrode current collecting foil; an insulating layer formed on at least one of a region of the positive current collector foil exposed portion excluding the positive current collector portion and a region of the negative current collector foil exposed portion excluding the negative current collector portion; A secondary battery comprising:

2. The insulating layers are formed at predetermined intervals along a long side direction of the positive electrode current collector foil or the negative electrode current collector foil. The secondary battery according to claim 1 .

3. the insulating layer is formed on both an area of ​​the positive current collector foil exposed portion excluding the positive current collector foil portion and an area of ​​the negative current collector foil exposed portion excluding the negative current collector foil portion. The secondary battery according to claim 1 .

4. The separator includes a first separator and a second separator, The first separator, the positive electrode plate, the second separator, and the negative electrode plate are stacked in order with their long sides aligned, and are wound around a winding axis set along the short side direction. The secondary battery according to claim 1 .

5. The battery case is a rectangular case having an outer shape of a substantially rectangular parallelepiped, The wound electrode body has an outer shape of a flat rectangular parallelepiped, the exposed portion of the positive electrode current collector foil is disposed in a stacked manner protruding from the negative electrode plate at one end in the winding axis direction, the negative electrode current collector foil exposed portion is disposed in a stacked manner protruding from the positive electrode plate at the other end portion in the winding axis direction, The wound electrode body is accommodated in the battery case such that the winding axis direction extends in the width direction of the battery case. The secondary battery according to claim 4 .

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