Electrode plate, non-aqueous electrolyte secondary battery, and method for manufacturing electrode plate

Abstract

An electrode plate which is to be contained in a wound or multilayer electrode body, and which is provided with: a band-like electrode plate core body; mixture layers that are formed on both surfaces of the electrode plate core body; and a tab that extends from one end of the electrode plate core body in the short-side direction. With respect to this electrode plate, the front edge of the electrode plate core body at the end from which the tab extends is covered by the mixture layers.

Description

[Technical field]

[0001] The present disclosure relates to an electrode plate, a non-aqueous electrolyte secondary battery, and a method for manufacturing an electrode plate. [Background technology]

[0002] The positive or negative electrode plates constituting the non-aqueous electrolyte secondary battery have a mixture layer on the surface of each core. If the active material contained in the mixture layer falls off inside the battery, an internal short circuit may occur, and the reliability of the battery can be improved by suppressing the fall-off of the active material. Since the fall-off of the active material is particularly likely to occur at the ends of the electrode plates, for example, Patent Document 1 discloses a secondary battery in which the mixture layer is removed from the ends of the electrode plates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-34009 A Summary of the Invention

[0004] In the method disclosed in Patent Document 1, there is a possibility that the active material may fall off at the interface between the exposed portion of the core and the portion where the mixture layer is formed on the surface of the core, and there is still room for improvement.

[0005] The electrode plate of one embodiment of the present disclosure is an electrode plate included in a wound or laminated electrode body, and is characterized in that it comprises a band-shaped electrode plate core, a mixture layer formed on both sides of the electrode plate core, and a tab extending from one end of the electrode plate core in the short direction, and at the end from which the tab extends, the tip of the electrode plate core is covered with the mixture layer.

[0006] A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure is a nonaqueous electrolyte secondary battery comprising a wound or stacked electrode assembly including the above-described electrode plate, an exterior body having an opening for accommodating the electrode assembly, and a sealing plate for sealing the opening and connecting to a tab, characterized in that the width of the end of the electrode plate core in the short direction is such that width a on one side is greater than width b on the other side, the tab is inclined at its base, and the angle formed between the surface on the side where the width of the end of the tab is a and the upper surface of the electrode assembly is an obtuse angle.

[0007] A method for manufacturing an electrode plate according to one embodiment of the present disclosure is a method for manufacturing an electrode plate included in a wound or laminated electrode body, and includes a mixture layer forming step of forming a band-shaped mixture layer on both sides of a band-shaped electrode plate core substrate along the longitudinal direction of the band-shaped electrode plate core substrate, and a cutting step of cutting out an electrode plate having a band-shaped electrode plate core having mixture layers formed on both sides thereof and a tab extending from one end of the electrode plate core in the short direction by irradiating one side of the electrode plate core substrate with laser light, and wherein the electrode plate cut out in the cutting step is characterized in that the tip of the electrode plate core is covered with the mixture layer at the end from which the tab extends.

[0008] According to one aspect of the present disclosure, it is possible to suppress the active material from falling off from the electrode plate. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a prismatic nonaqueous electrolyte secondary battery as an example of the embodiment. [Diagram 2] FIG. 2 is a front vertical cross-sectional view seen in the direction AA in FIG. [Diagram 3] FIG. 3 is a perspective view of the electrode group of the nonaqueous electrolyte secondary battery shown in FIG. 2, showing the outer wound end of the electrode body on the near side in a developed state. [Figure 4] FIG. 4 is a front view showing a negative electrode plate in an example of the embodiment in a developed state. [Diagram 5] FIG. 5 is a cross-sectional view taken along line CC in FIG. [Figure 6]FIG. 6 is a photograph taken by a scanning electron microscope of the vicinity of the tip of a cross section of a negative electrode plate in an example of the embodiment cut in the thickness direction. [Figure 7] FIG. 7 is an enlarged cross-sectional view of the periphery of the negative electrode tab in a cross section taken along line BB in FIG. [Figure 8] FIG. 8 is a diagram illustrating a method for cutting the negative electrode plate in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An example of an embodiment will be described in detail below. In this specification, the vertical direction on the paper surface of Figures 1 to 3 may be expressed as "upper, lower", the horizontal direction as "left, right", and the depth direction as "front, back".

[0011] With reference to FIG. 1 and FIG. 2, the configuration of a nonaqueous electrolyte secondary battery 100 as an example of an embodiment will be described. FIG. 1 is a perspective view showing the appearance of a nonaqueous electrolyte secondary battery 100 as an example of an embodiment, and FIG. 2 is a front longitudinal sectional view seen in the AA direction in FIG. 1. As shown in FIG. 1 and FIG. 2, the nonaqueous electrolyte secondary battery 100 includes a battery case 16 having an exterior body 1 with an opening at the top and a sealing plate 2 that seals the opening. The exterior body 1 and the sealing plate 2 are preferably made of metal, and can be made of aluminum or an aluminum alloy, for example. The exterior body 1 is a rectangular, bottomed, cylindrical exterior body having a bottom and a side wall and an opening at a position opposite to the bottom. The nonaqueous electrolyte secondary battery 100 shown in FIG. 1 is an example of a rectangular nonaqueous electrolyte secondary battery having a rectangular battery case 16, but the nonaqueous electrolyte secondary battery of this embodiment is not limited thereto. For example, the battery case may have an opening shaped like a circle, an oval, or an ellipse, or may be a laminated nonaqueous electrolyte secondary battery having a battery case made of a laminate sheet formed by laminating a metal foil with a resin sheet. The sealing plate 2 is connected to the edge of the opening of the rectangular exterior body 1 by laser welding or the like.

[0012] The sealing plate 2 has an electrolyte injection hole 13. After an electrolyte, which will be described later, is injected into the electrolyte injection hole 13, the hole is sealed with a sealing plug 14. The sealing plate 2 also has a gas exhaust valve 15. This gas exhaust valve 15 operates when the pressure inside the battery reaches or exceeds a predetermined value, and exhausts gas inside the battery to the outside of the battery.

[0013] A positive electrode terminal 4 is attached to the sealing plate 2 so as to protrude outside the battery case 16. Specifically, the positive electrode terminal 4 is inserted into a positive electrode terminal attachment hole formed in the sealing plate 2, and is attached to the sealing plate 2 in a state in which it is electrically insulated from the sealing plate 2 by an external insulating member 9 arranged on the outside of the battery of the positive electrode terminal attachment hole, and an internal insulating member 8 arranged on the inside of the battery. The positive electrode terminal 4 is electrically connected to a positive electrode current collector 5 inside the battery case 16. The positive electrode current collector 5 is provided on the sealing plate 2 with the internal insulating member 8 sandwiched therebetween. The internal insulating member 8 and the external insulating member 9 are each preferably made of resin.

[0014] In addition, a negative electrode terminal 6 is attached to the sealing plate 2 so as to protrude outside the battery case 16. Specifically, the negative electrode terminal 6 is inserted into a negative electrode terminal attachment hole formed in the sealing plate 2, and is attached to the sealing plate 2 in a state in which it is electrically insulated from the sealing plate 2 by an external insulating member 11 arranged on the outside of the battery of the negative electrode terminal attachment hole, and an internal insulating member 10 arranged on the inside of the battery. The negative electrode terminal 6 is electrically connected to a negative electrode current collector 7 inside the battery case 16. The negative electrode current collector 7 is provided on the sealing plate 2 with the internal insulating member 10 sandwiched therebetween. It is preferable that each of the internal insulating member 10 and the external insulating member 11 is made of resin.

[0015] The nonaqueous electrolyte secondary battery 100 includes an electrode group 3 and an electrolytic solution, and the exterior body 1 accommodates the wound electrode group 3 and the electrolytic solution. As described below, the electrode group 3 includes two electrode bodies having a wound structure in which a positive electrode plate 20 and a negative electrode plate 30 are wound with a separator 40 interposed therebetween. At the upper part of the electrode group 3, a positive electrode tab 28 and a negative electrode tab 38 protrude from the positive electrode plate 20 and the negative electrode plate 30, respectively. The positive electrode tab 28 and the negative electrode tab 38 are bent in the depth direction and are connected to the positive electrode collector 5 and the negative electrode collector 7, respectively, by welding or the like. The electrode body is not limited to a wound type, and may be a laminated type.

[0016] As shown in FIG. 2, the nonaqueous electrolyte secondary battery 100 may include an insulating sheet 12 disposed between the electrode group 3 and the exterior body 1. The insulating sheet 12 may have a bottomed box-like or bag-like shape with an opening at the top, similar to the exterior body 1. By having the insulating sheet 12 have a bottomed box-like or bag-like shape with an opening at the top, the electrode group 3 may be inserted through the opening of the insulating sheet 12, and the electrode group 3 may be covered by the insulating sheet 12. The material of the insulating sheet 12 is not particularly limited as long as it has electrical insulation, chemical stability that is not corroded by the electrolyte, and electrical stability that does not electrolyze against the voltage of the nonaqueous electrolyte secondary battery 100. As the material of the insulating sheet 12, for example, a resin material such as polyethylene, polypropylene, or polyethylene fluoride may be used from the viewpoints of industrial versatility, manufacturing cost, and quality stability.

[0017] The electrolytic solution includes a solvent and an electrolyte salt dissolved in the solvent. The solvent may be a non-aqueous solvent. For example, carbonates, esters, ethers, nitriles, amides, and mixed solvents of two or more of these may be used as the non-aqueous solvent. Examples of carbonates include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, and vinylene carbonate; and chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate. The non-aqueous solvent may contain a halogen-substituted product in which at least a part of the hydrogen of the above-mentioned solvent is substituted with a halogen atom such as fluorine. The electrolytic solution is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel-like polymer or the like. The electrolyte salt includes a lithium salt. The lithium salt may be LiPF6 or the like, which is generally used as a supporting salt in the conventional non-aqueous electrolyte secondary battery 100. In addition, an additive such as vinylene carbonate (VC) may be added as appropriate.

[0018] FIG. 3 is a perspective view of an electrode group 3 consisting of two wound electrode bodies 3a and 3b, and shows the outer end of the electrode body 3a on the front side developed. Each of the electrode bodies 3a and 3b has a wound structure in which a positive electrode plate 20 and a negative electrode plate 30 are wound with a separator 40 interposed therebetween. Since each of the electrode bodies 3a and 3b is pressed and molded after being wound, the front and rear surfaces are approximately parallel, and the left and right ends are curved to form a flat shape. The number of electrode bodies constituting the electrode group 3 is not limited to two, and may be one or three or more. In addition, a bundle of positive electrode tabs 28 (hereinafter sometimes referred to as a "positive electrode tab group") protrudes upward from each of the electrode bodies 3a and 3b. A bundle of negative electrode tabs 38 (hereinafter sometimes referred to as a "negative electrode tab group") also protrudes upward from each of the electrode bodies 3a and 3b, similar to the positive electrode tab group. The number of positive electrode tab groups and negative electrode tab groups, and the number of each electrode tab constituting them are not particularly limited.

[0019] The separator 40 is made of a porous sheet having ion permeability and insulation properties. Specific examples of the porous sheet include a microporous membrane, a woven fabric, and a nonwoven fabric. The separator 40 is preferably made of an olefin resin such as polyethylene or polypropylene, or cellulose. The separator 40 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. The separator 40 may also be a multi-layer separator including a polyethylene layer and a polypropylene layer, and the separator 40 may have a surface coated with a resin such as an aramid resin, or inorganic fine particles such as alumina or titania.

[0020] Hereinafter, the positive electrode plate 20 and the negative electrode plate 30 constituting the electrode group 3 will be described in detail with reference to FIGS.

[0021] First, the positive electrode plate 20 will be described. As shown in Fig. 3, the positive electrode plate 20 has a strip-shaped positive electrode core 22, a positive electrode mixture layer 24 formed on both sides of the positive electrode core 22, and a positive electrode tab 28 extending upward from one end of the positive electrode core 22 in the short side direction.

[0022] The positive electrode core 22 is made of a foil of a metal such as aluminum that is stable within the potential range of the positive electrode plate 20. The thickness of the positive electrode core 22 is, for example, 10 to 20 μm.

[0023] The positive electrode mixture layer 24 is formed in a band shape on at least a part of the surface of the positive electrode core 22 along the longitudinal direction of the positive electrode core 22. The positive electrode mixture layer 24 is preferably provided at corresponding positions on both sides of the positive electrode core 22. The positive electrode mixture layer 24 contains a positive electrode active material, a binder, and a conductive material, and can be produced by applying a positive electrode active material slurry containing a positive electrode active material, a binder, a conductive material, and the like to both sides of the positive electrode core 22, drying the coating, and then compressing it with a roller or the like.

[0024] The positive electrode active material is generally Li 1+x M a O 2+b(wherein x, a, and b satisfy the conditions of x + a = 1, -0.2 < x ≤ 0.2, and -0.1 ≤ b ≤ 0.1, M contains Ni and Co, and contains at least one element selected from the group consisting of Mn and Al) and contains a lithium metal composite oxide represented by the formula. As the positive electrode active material, a small amount of other lithium metal composite oxides or the like may be contained, but it is preferable that the lithium metal composite oxide represented by the above general formula be the main component.

[0025] The lithium metal composite oxide may contain elements other than Ni, Co, Mn, and Al. Examples of other elements include alkali metal elements other than Li, transition metal elements other than Ni, Co, and Mn, alkaline earth metal elements, Group 12 elements, Group 13 elements other than Al, and Group 14 elements. Specifically, Zr, B, Mg, Ti, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, etc. can be exemplified. In addition, inorganic compound particles such as zirconium oxide, tungsten oxide, aluminum oxide, and lanthanoid-containing compounds may be adhered to the particle surface of the lithium metal composite oxide.

[0026] The particle size of the lithium metal composite oxide is not particularly limited, but for example, it is preferable that the average particle size is 2 μm or more and less than 30 μm. When the average particle size is less than 2 μm, the conduction by the conductive material in the positive electrode mixture layer 24 may be inhibited and the resistance may increase. On the other hand, when the average particle size is 30 μm or more, the load characteristics may decrease due to a decrease in the reaction area. The average particle size is the volume average particle size measured by the laser diffraction method, and means the median diameter at which the volume integration value is 50% in the particle size distribution. The average particle size can be measured, for example, using a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba, Ltd.).

[0027] Examples of the binder contained in the positive electrode mixture layer 24 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide-based resins, acrylic-based resins, and polyolefin-based resins. These binders may be used alone or in combination of two or more.

[0028] Examples of the conductive material contained in the positive electrode mixture layer 24 include carbon materials such as carbon black (CB), acetylene black (AB), ketjen black, graphite, etc. These conductive materials may be used alone or in combination.

[0029] The filling density of the positive electrode mixture layer 24 is 2.0 g / cm 3 ~4.0g / cm 3 The higher the packing density of the positive electrode mixture layer 24, the larger the capacity of the battery.

[0030] 3, the positive electrode mixture layer uncoated portion 26 is a region on the surface of the positive electrode core 22 where the positive electrode mixture layer 24 is not formed and the positive electrode core 22 is exposed. Similarly to the negative electrode plate 30 described below, the positive electrode plate 20 may not have the positive electrode mixture layer uncoated portion 26 and the positive electrode mixture layer 24 may be formed on the entire surface of the positive electrode core 22. In addition, in the short direction of the positive electrode core 22, the tip of the end on the side from which the positive electrode tab 28 extends may be covered with the positive electrode mixture layer 24.

[0031] The positive electrode tab 28 extends from one end in the short direction of the positive electrode core 22. The positive electrode plate 20 has a plurality of positive electrode tabs 28 in the longitudinal direction of the positive electrode core 22, and the distance between the positive electrode tabs 28 in the longitudinal direction of the positive electrode core 22 is adjusted so as to be aligned when wound.

[0032] A protective layer having a higher electrical resistance than the positive electrode core 22 may be provided so as to cover a part or all of the positive electrode mixture layer uncoated portion 26 including the base of the positive electrode tab 28. The protective layer is provided to prevent current from passing through unintended portions of the positive electrode mixture layer uncoated portion 26. The thickness of the protective layer is, for example, 20 μm to 120 μm, and may be 50 μm to 100 μm. The protective layer may contain ceramic particles such as alumina, zirconia, titania, and silica, and a binder such as polyvinylidene fluoride (PVdF).

[0033] The shape of the positive electrode tab 28 is not particularly limited, but may be, for example, a symmetrical shape. The positive electrode tabs 28 may each have a different shape, but preferably have the same shape in order to be bundled together.

[0034] Next, the negative electrode plate 30 will be described. As shown in Fig. 3, the negative electrode plate 30 has a strip-shaped negative electrode core 32, a negative electrode mixture layer 34 formed on both sides of the negative electrode core 32, and a negative electrode tab 38 extending upward from one end of the negative electrode core 32 in the short side direction.

[0035] The negative electrode core 32 may be made of a foil of a metal such as copper that is stable within the potential range of the negative electrode plate 30. The negative electrode core 32 has a thickness of, for example, 5 to 15 μm.

[0036] The negative electrode mixture layer 34 is formed in a band shape on the surface of the negative electrode core 32 along the longitudinal direction of the negative electrode core 32, and may be formed on the entire surface of the negative electrode core 32. The negative electrode mixture layer 34 is preferably provided at corresponding positions on both sides of the negative electrode core 32. The negative electrode plate 30 contains a negative electrode active material and a binder. The negative electrode plate 30 can be produced by applying a negative electrode active material slurry containing a negative electrode active material and a binder, etc., onto the negative electrode core 32, drying the coating, and then compressing it with a roller or the like to form the negative electrode mixture layer 34 on both sides of the negative electrode core 32.

[0037] The negative electrode active material may be, for example, low-crystalline carbon-coated graphite formed by forming a coating of low-crystalline carbon on the surface of graphite. Low-crystalline carbon is a carbon material in which the graphite crystal structure is not developed and is in an amorphous or microcrystalline turbostratic state, or a carbon material that is not spherical or flaky but has a very fine particle size. For example, a carbon material having a d(002) interplanar distance of more than 0.340 nm by X-ray diffraction is low-crystalline carbon. In addition, a carbon material having an average particle size of 1 μm or less of primary particles observed and measured by a scanning electron microscope (SEM) or the like is also low-crystalline carbon. Specific examples of low-crystalline carbon include hard carbon (hardly graphitizable carbon), soft carbon (easily graphitizable carbon), carbon black such as acetylene black, ketjen black, thermal black, and furnace black, carbon fiber, activated carbon, and the like. The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions, and examples of the material that can be used include carbon materials such as natural graphite and artificial graphite, metals that can be alloyed with Li, such as silicon (Si) and tin (Sn), and oxides containing metal elements such as Si and Sn. The negative electrode mixture layer 34 may also contain a lithium titanium composite oxide.

[0038] A known binder can be used for the binder contained in the negative electrode mixture layer 34, and fluororesins such as PTFE and PVdF, PAN, polyimide resins, acrylic resins, and polyolefin resins can be used, as in the case of the positive electrode mixture layer 24. Examples of binders used when preparing the negative electrode active material slurry using an aqueous solvent include CMC or a salt thereof, styrene butadiene rubber (SBR), polyacrylic acid (PAA) or a salt thereof, and polyvinyl alcohol (PVA).

[0039] The packing density of the negative electrode mixture layer 34 is 1.0 g / cm 3 ~2.0g / cm 3 The higher the packing density of the negative electrode mixture layer 34, the larger the capacity of the battery.

[0040] Next, the negative electrode plate 30 will be described with reference to Figures 4 and 5. Figure 4 is a front view showing the negative electrode plate 30 in an expanded state, and Figure 5 is a cross-sectional view taken along line CC in Figure 4. As shown in Figure 4, the negative electrode plate 30 has a plurality of negative electrode tabs 38 in the longitudinal direction of the negative electrode core 32, and the distance between each of the negative electrode tabs 38 in the longitudinal direction of the negative electrode core 32 is adjusted so as to be aligned when wound.

[0041] The shape of the negative electrode tab 38 is not particularly limited, but may be, for example, a symmetrical shape. Furthermore, the negative electrode tabs 38 may each have a different shape, but preferably have the same shape in order to be bundled together.

[0042] 5, at the end portion on the side where the negative electrode tab 38 extends, the tip portion 36 of the negative electrode core 32 is covered with the negative electrode mixture layer 34. As a result, at the tip portion 36, there is no interface between the part where the negative electrode core 32 is exposed and the part where the negative electrode mixture layer 34 is formed on the surface of the negative electrode core 32, so that it is possible to suppress the falling off of the negative electrode active material from the negative electrode plate 30. Here, the tip portion 36 refers to the end face of the negative electrode core 32 at the end portion on the side where the negative electrode tab 38 of the negative electrode core 32 extends, and a part on the surface of the negative electrode core 32 adjacent to the end face of the negative electrode core 32.

[0043] The thickness of the negative electrode mixture layer 34 covering the tip portion 36 may be thinner than the thickness of one side of the negative electrode mixture layer 34 formed on the inner side of the tip portion 36 of the negative electrode core 32 .

[0044] Furthermore, the width of the tip portion 36 in the short side direction of the negative electrode core 32 may be such that the width a on one surface is greater than the width b on the other surface. In Fig. 5, the tip portion 36 is composed of the end face of the negative electrode core 32 and portions of width a and width b adjacent to the end face of the negative electrode core 32 on the surface of the negative electrode core 32. Furthermore, the thickness of the negative electrode mixture layer 34 covering the tip portion 36 in Fig. 5 is approximately the same, but may be non-uniform.

[0045] The width a of the tip 36 on one surface is, for example, 30 μm to 100 μm, and the width b of the tip 36 on the other surface is, for example, 5 μm to 50 μm.

[0046] 6 is a photograph taken by a scanning electron microscope of the vicinity of the tip 36 in a cross section of the negative electrode plate 30 cut in the thickness direction. The negative electrode plate 30 has a thickness of 169 μm, and the negative electrode core 32 is a copper plate having a thickness of 8 μm. The negative electrode mixture layer 34 is made of 98.3 mass % graphite, 0.7 mass % CMC, and 1.0 mass % SBR, and has a packing density of 1.6 g / cm. 3 The manufacturing method of the negative electrode plate 30 will be described in detail later, but the vicinity of the tip 36 is cut by a laser beam. The negative electrode plate 30 was irradiated with a laser beam having a wavelength of 1.06 μm, a peak output of 37.5 kW, a repetition frequency of 20 kHz, and a pulse width of 100 ns at a scanning speed of 30 m / min while being focused by a lens with a focal length of 100 mm. The energy per plate thickness was 0.89 mJ / mm·μm. The energy per plate thickness is expressed as "energy per plate thickness = pulse energy (mJ) × number of irradiations per mm / plate thickness (μm)". Here, the number of irradiations per mm is the number of times the laser beam is irradiated while the plate advances 1 mm. The laser beam was irradiated so that the negative electrode plate 30 was approximately at the position of the beam waist of the laser beam. In FIG. 6, the tip 36 is covered with the negative electrode mixture layer 34 as in the cross-sectional view of the negative electrode plate 30 shown in FIG. 5. The thickness of the negative electrode mixture layer covering the tip portion is thinner than the thickness of one side of the negative electrode mixture layer formed on the inner side of the tip portion .

[0047] 6, the tip portion 36 may have a claw shape in a cross section cut along the thickness direction of the negative electrode core 32. This improves the binding strength between the tip portion 36 and the negative electrode mixture layer 34, thereby further preventing the active material from falling off. In addition, since the claw shape is covered by the negative electrode mixture layer 34, it is possible to prevent the claw shape from contacting and damaging the separator 40.

[0048] Next, the negative electrode tab 38 in the nonaqueous electrolyte secondary battery 100 will be described with reference to FIG. 7. FIG. 7 is a cross-sectional view showing an enlarged view of the periphery of the negative electrode tab 38 in a cross section taken along the line BB in FIG. 2. The negative electrode tab 38a extending from the electrode body 3a has its root inclined toward the front side in the depth direction, and is connected to the negative electrode current collector 7 attached to the sealing plate 2 after bending. Here, the surface of the tip portion 36 having a width a, which is not shown in FIG. 7, faces the back side in the depth direction, and the angle α1 formed between the surface of the tip portion 36 of the negative electrode tab 38a having a width a and the upper surface 50a of the electrode body 3a may be an obtuse angle. In addition, the negative electrode tab 38b extending from the electrode body 3b has its root inclined toward the back side in the depth direction, and is connected to the negative electrode current collector 7 attached to the sealing plate 2 after bending. 7, the surface of the tip portion 36 having a width a faces toward the front side in the depth direction, and the angle α2 between the surface of the tip portion 36 of the negative electrode tab 38b having a width a and the upper surface 50b of the electrode body 3b may be an obtuse angle. α1 and α2 may be the same angle or different angles.

[0049] 3, the surfaces of the tip portions 36 can be aligned by moving the negative electrode tabs 38a, 38b to only one side with respect to the winding cores of the electrode bodies 3a, 3b. In FIG. 3, the negative electrode tabs 38a, 38b are moved to the side closer to the exterior body 1 in the depth direction, so that when the electrode group 3 is housed in the nonaqueous electrolyte secondary battery 100 as shown in FIG. 7, the surface of the tip portion 36 of the negative electrode tab 38 on the side with width a faces the inside of the winding.

[0050] Next, a method for manufacturing the negative electrode plate 30 will be described. The method for manufacturing the negative electrode plate 30 includes a mixture layer forming step and a cutting step. In the mixture layer forming step, a band-shaped negative electrode mixture layer 34 is formed on both sides of the substrate for the negative electrode core 32 along the longitudinal direction of the substrate for the negative electrode core 32. The negative electrode mixture layer 34 can be produced by applying a negative electrode active material slurry containing a negative electrode active material and a binder, etc., to the surface of the substrate for the negative electrode core 32, drying the coating, and then compressing it with a roller or the like to form the negative electrode mixture layer 34 on both sides of the negative electrode core 32. In the cutting step, a laser beam is irradiated onto one side of the substrate for the negative electrode core 32 to cut out a negative electrode plate 30 having a band-shaped negative electrode core 32 with the negative electrode mixture layer 34 formed on both sides and a negative electrode tab 38 extending from one end of the negative electrode core 32 in the short direction. In the negative electrode plate 30 cut out in the cutting step, the tip portion 36 of the negative electrode core 32 is covered with the negative electrode mixture layer 34 at the end portion from which the tab extends.

[0051] Hereinafter, a method for cutting the negative electrode plate 30 will be described, but the positive electrode plate 20 may be cut in the same manner. FIG. 8 is a diagram for explaining an example of a method for cutting the negative electrode plate 30. The dotted lines in FIG. 8 indicate the scanning traces of the laser light. A band-shaped negative electrode mixture layer 34 is formed on both sides of the substrate for the negative electrode core 32 along the longitudinal direction of the substrate for the band-shaped negative electrode core 32, and the negative electrode core 32 is exposed in the portion where the negative electrode mixture layer 34 is not formed. In the cutting step, the laser light is scanned according to the shape of the tip portion 36 and the negative electrode tab 38. The tip portion 36 is cut out by scanning the portion where the negative electrode mixture layer 34 is formed, which is on the inner side of the boundary between the portion where the negative electrode core 32 is exposed and the portion where the negative electrode mixture layer 34 is formed, with the laser light. The negative electrode tab 38 protrudes outward from the tip portion 36, and is cut out by cutting the portion where the negative electrode core 32 is exposed, including the portion where the negative electrode mixture layer 34 is formed at the base portion.

[0052] The characteristics of the laser light and the laser irradiation optical system are not particularly limited, but by appropriately adjusting them according to the thickness, composition, etc. of the negative electrode core 32 and the negative electrode mixture layer 34 within the range of conditions in Table 1, for example, the desired negative electrode plate 30 can be manufactured.

[0053] [Table 1]

[0054] If the repetition frequency is low, the pulse energy increases and the cut surface of the electrode plate becomes rough, so a repetition frequency of 10 kHz or more is preferable, and if the repetition frequency is high, the pulse energy decreases, resulting in poor workability and a slow line speed, so a repetition frequency of 150 kHz or less is preferable.

[0055] If the energy per unit thickness of the electrode plate is too small, the mixture will peel off from the core surface, so a value of 0.33 mJ / mm μm or more is preferable, and if the energy per unit thickness of the electrode plate is too large, the width a of the tip portion 36 will become too large, so a value of 4.13 mJ / mm μm or less is preferable.

[0056] The pulse width is preferably from 10 to 300 ns, and more preferably from 50 to 200 ns.

[0057] To scan the laser light, the substrate for the negative electrode core 32 may be moved, or the laser light may be moved using, for example, a galvano scanner system. In addition, the end on the opposite side to the side from which the negative electrode tab 38 extends, the winding start end, and the winding end may be cut using a laser light as described above, or may be cut using a slit blade.

[0058] As described above, according to the electrode plate of this embodiment, it is possible to suppress the active material from falling off. [Explanation of symbols]

[0059] 1 Exterior body 2 Sealing plate 3 electrode groups 4 Positive terminal 5 Positive electrode current collector 6 Negative terminal 7 Negative electrode current collector 8,10 Inner insulating member 9,11 External insulating member 12 Insulation sheet 13 Electrolyte injection hole 14 Sealing plug 15 Gas exhaust valve 16 Battery case 20 Positive electrode plate 22 Positive electrode core 24 Positive electrode mixture layer 28 Positive tab 30 Negative plate 32 Negative electrode core 34 Negative electrode mixture layer 36 Tip 38 Negative tab 40 Separator 50 (Electrode body) top surface 100 Nonaqueous electrolyte secondary battery

Claims

1. An electrode plate included in a wound or laminated electrode body, A strip-shaped electrode plate core body, A mixture layer formed on both sides of the electrode plate core; A tab extending from one end of the electrode plate core in a short direction, At the end portion on the side where the tab extends, the entire tip portion of the electrode core is covered with the mixture layer so that there is no interface between a portion where the electrode core is exposed and a portion where the mixture layer is formed on the surface of the electrode core, a thickness of the mixture layer covering the tip portion is smaller than a thickness of one surface of the mixture layer formed on an inner side of the tip portion of the electrode plate core; A plate in which the width a of the tip portion in the short side direction of the electrode plate core body on one surface is larger than the width b on the other surface.

2. The electrode plate according to claim 1 , wherein the tip portion has a claw shape in a cross section cut along a thickness direction of the electrode plate core body.

3. 3. The electrode plate according to claim 1 or 2, wherein the electrode plate is a negative electrode plate.

4. A wound or laminated electrode assembly including the electrode plate according to claim 1; an exterior body having an opening for accommodating the electrode assembly; a sealing plate that seals the opening and connects to the tab, the tab has an inclined base, and the angle between the surface of the tip of the tab on the side having width a and the upper surface of the electrode body is an obtuse angle.

5. The electrode body is wound, 5. The nonaqueous electrolyte secondary battery according to claim 4, wherein the surface of the electrode body on the side where the tip portion has width a faces an inner side of the winding.

6. A method for manufacturing an electrode plate included in a wound or laminated electrode body, comprising the steps of: A mixture layer forming step of forming a band-shaped mixture layer on both sides of the electrode core substrate along the longitudinal direction of the band-shaped electrode core substrate; a cutting step of cutting out an electrode plate having a band-shaped electrode plate core having the mixture layers formed on both sides thereof and a tab extending from one end in a short side direction of the electrode plate core by irradiating one side of the electrode plate core substrate with a laser beam, In the electrode plate cut out in the cutting step, At the end portion on the side where the tab extends, the entire tip portion of the electrode core is covered with the mixture layer so that there is no interface between a portion where the electrode core is exposed and a portion where the mixture layer is formed on the surface of the electrode core, a thickness of the mixture layer covering the tip portion is smaller than a thickness of one surface of the mixture layer formed on an inner side of the tip portion of the electrode plate core; A method for manufacturing an electrode plate, wherein a width a of the tip portion in the short side direction of the electrode plate core body on one surface is larger than a width b on the other surface.

7. 7. A method for manufacturing an electrode plate included in the wound or laminated electrode body according to claim 6, wherein the irradiation conditions of the laser light are a wavelength of 1.06 μm, a repetition frequency of 10 to 150 kHz, energy per electrode plate thickness of 0.33 mJ / mm μm to 2.00 mJ / mm μm, and a pulse width of 30 ns to 300 ns.

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