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

Abstract

This positive electrode plate, included in a rolled electrode body, is characterized by comprising a belt-shape positive electrode core, a positive electrode active material layer which, along the long direction of the positive electrode core, is formed in a belt shape on at least part of the surface of the positive electrode core, and a positive electrode tab which extends in the short direction of the positive electrode core from the active material layer-uncoated area of the surface of the positive electrode core where the positive electrode active material layer is not formed, and the root width H1 and the maximum width H2 of the positive electrode tab satisfy the relation 0.4×H2 ≤ H1 ≤ 0.9×H2.

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] In recent years, there has been an increasing demand for higher capacity non-aqueous electrolyte secondary batteries used in vehicles such as electric vehicles. Therefore, it has become necessary to highly compress and introduce more active material into the active material layer formed on the surface of the electrode plate core body to increase the density of the active material layer. The region of the electrode plate core body having the active material layer on the surface is thicker than the active material layer uncoated portion where the electrode plate core body is exposed and the tab extending from the active material layer uncoated portion, and is therefore easily stretched by compression. Therefore, when the active material layer is compressed, a strong stress is applied to the periphery of the interface between the active material layer and the active material layer uncoated portion, and the core body may develop a crack extending from the base of the tab. Patent Document 1 discloses a method for removing the starting point of the crack in the core body by forming a structure in which the first electrode plate tab extends from the first electrode plate active material layer while the core body of the first electrode plate and the active material layer formed on its surface are notched at the base of the tab. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 204184 Summary of the Invention

[0004] However, the method disclosed in Patent Document 1 reduces battery capacity because the active material layer is cut off, and there is also a possibility that the active material may fall off from the cut-out portions of the active material layer, so there is still room for improvement.

[0005] Therefore, an object of the present disclosure is to provide an electrode plate in which the occurrence of cracks in the electrode plate core body is suppressed.

[0006] The electrode plate of one embodiment of the present disclosure is an electrode plate included in a wound electrode body, and has a band-shaped electrode plate core, an active material layer formed in a band shape on at least a part of the surface of the electrode plate core along the longitudinal direction of the electrode plate core, and a tab extending in the lateral direction of the electrode plate core from an uncoated portion of the surface of the electrode plate core where the active material layer is not formed, and is characterized in that the base width H1 and maximum width H2 of the tab satisfy the relationship 0.4×H2≦H1≦0.9×H2.

[0007] A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure is characterized by comprising a wound electrode assembly including the above-described electrode plate, and a battery case that houses the electrode assembly.

[0008] 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 electrode body, the method comprising the steps of: preparing a precursor of an electrode plate having a band-shaped electrode plate core; active material slurry applied in a band shape to at least a portion of the surface of the electrode plate core along the longitudinal direction of the electrode plate core; and a tab extending in the lateral direction of the electrode plate core from an uncoated portion of the surface of the electrode plate core where the active material slurry is not applied, the tab having a base width H1 and a maximum width H2 that satisfy the relationship 0.4×H2≦H1≦0.9×H2; and compressing the precursor.

[0009] According to one aspect of the present disclosure, it is possible to suppress the occurrence of cracks in the electrode plate core while responding to an increase in the capacity of the battery. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view showing a prismatic nonaqueous electrolyte secondary battery according to an embodiment of the present invention; [Diagram 2] 2 is a front vertical cross-sectional view seen in the direction AA of FIG. 1. [Diagram 3] 3 is a perspective view of a wound electrode body of the nonaqueous electrolyte secondary battery shown in FIG. 2, with the outer end of the winding developed. FIG. [Figure 4] 1(a) to 1(f) are enlarged views of the periphery of a positive electrode tab in one example of an embodiment. [Diagram 5]FIG. 13 illustrates a case where the positive electrode tabs are misaligned in an example embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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".

[0012] The configuration of a nonaqueous electrolyte secondary battery 100 as an example of the embodiment will be described with reference to FIG. 1 and FIG. 2. FIG. 1 is a perspective view showing the appearance of the nonaqueous electrolyte secondary battery 100 as an example of the 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 the present 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] The nonaqueous electrolyte secondary battery 100 includes an electrode assembly 3 and an electrolyte, and an exterior housing 1 accommodates the wound electrode assembly 3 and the electrolyte. As described below with reference to Fig. 3, the electrode assembly 3 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. At the top of the electrode assembly 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, and the positive electrode tab 28 and the negative electrode tab 38 are connected to the positive electrode collector 5 and the negative electrode collector 7, respectively, by welding or the like.

[0017] As shown in FIG. 2, the nonaqueous electrolyte secondary battery 100 may include an insulating sheet 12 disposed between the electrode body 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. The insulating sheet 12 may have a bottomed box-like or bag-like shape with an opening at the top, so that the electrode body 3 can be inserted through the opening of the insulating sheet 12 and the electrode body 3 can 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.

[0018] 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.

[0019] FIG. 3 is a perspective view of the electrode body 3, and is a view in which the outer end of the winding is developed. The electrode body 3 has a wound structure in which the positive electrode plate 20 and the negative electrode plate 30 are wound with a separator 40 interposed therebetween. The electrode body 3 is pressed and molded after winding, so that the front and back surfaces are approximately parallel and the left and right ends are curved to form a flat shape. In addition, two sets of four positive electrode tabs 28 (hereinafter sometimes referred to as "positive electrode tab groups") each protrude upward from the main body of the electrode body 3. Two sets of four negative electrode tabs 38 (hereinafter sometimes referred to as "negative electrode tab groups") each protrude upward from the main body of the electrode body 3, similar to the positive electrode tab groups. 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. Hereinafter, the positive electrode plate 20, negative electrode plate 30, and separator 40 constituting the electrode body 3, and in particular the positive electrode tabs 28, will be described in detail with reference to FIGS. 3 to 5.

[0020] [Positive electrode] As shown in FIG. 3, the positive electrode plate 20 has a strip-shaped positive electrode core 22, a positive electrode active material layer 24 formed on the surface of the positive electrode core 22, and a positive electrode tab 28 extending from one end of the positive electrode core 22 in the short side direction.

[0021] 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.

[0022] The positive electrode active material 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 active material layer 24 contains a positive electrode active material, a binder, and a conductive material, and is preferably provided at corresponding positions on both sides of the positive electrode core 22. The positive electrode active material layer 24 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.

[0023] 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. 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.

[0024] 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.

[0025] 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 active material 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 deteriorate 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.).

[0026] Examples of the binder contained in the positive electrode active material layer 24 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide-based resins, acrylic resins, and polyolefin-based resins. These binders may be used alone or in combination of multiple types.

[0027] Examples of the conductive material contained in the positive electrode active material 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.

[0028] The packing density of the positive electrode active material layer 24 is 3.5 g / cm 3 The packing density of the positive electrode active material layer 24 may be 4.0 g / cm 3 The higher the packing density of the positive electrode active material layer 24, the larger the capacity of the battery.

[0029] The positive electrode active material layer uncoated portion 26 is a region on the surface of the positive electrode core 22 where the positive electrode active material layer 24 is not formed and the positive electrode core 22 is exposed. The width of the positive electrode active material layer uncoated portion 26 is preferably greater than 0 mm and equal to or less than 3 mm, and more preferably equal to or less than 1 mm. The positive electrode active material layer uncoated portion 26 having such a width between the positive electrode active material layer 24 and the positive electrode tab 28 relieves stress generated when the positive electrode active material layer 24 is compressed, and suppresses the occurrence of cracks originating from the base of the positive electrode tab 28.

[0030] The positive electrode tab 28 extends in the short direction of the positive electrode core 22 from a positive electrode active material layer uncoated portion 26 on the surface of the positive electrode core 22 where the positive electrode active material layer 24 is not formed. 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.

[0031] A protective layer having a higher electrical resistance than the positive electrode core 22 may be provided so as to cover the positive electrode active material 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 active material 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).

[0032] Next, the shape of the positive electrode tab 28 will be described with reference to Fig. 4. (a) to (f) of Fig. 4 are each an enlarged view of the periphery of the positive electrode tab 28 in one example of the embodiment.

[0033] 4(a) shows a case where the angle α formed by the side of the positive electrode tab 28 and the side parallel to the longitudinal direction of the positive electrode core 22 at the intersection point of the side of the positive electrode tab 28 and the positive electrode core 22 at the base of the positive electrode tab 28 is an acute angle. The positive electrode tab 28 has a bilaterally symmetrical shape having a band-shaped main body portion and a base portion narrower than the main body portion.

[0034] The root width H1 and maximum width H2 of the positive electrode tab 28 satisfy the relationship 0.4×H2≦H1≦0.9×H2. The root width H1 indicates the width of the root of the positive electrode tab 28, and the maximum width H2 indicates the maximum width of the main body of the positive electrode tab 28. When the packing density of the positive electrode active material layer 24 is increased, cracks at the root of the positive electrode tab 28 can be suppressed by making the value of the root width H1 smaller. When the packing density of the positive electrode active material layer 24 is 3.5 g / cm 3 ~3.7g / cm 3If the root width H1 is 15 mm or less, the positive electrode tab 28 and the positive electrode active material layer uncoated portion 26 around the positive electrode tab 28 are easily deformed, and the stress generated when the positive electrode active material layer 24 is compressed is alleviated, so that it is possible to suppress the occurrence of cracks from the root of the positive electrode tab 28. In addition, the maximum width H2 is, for example, 10 mm to 40 mm, and more preferably 30 mm or less. If the length of the positive electrode plate 20 is long, it becomes difficult to align the positive electrode tab group. When the length of the positive electrode plate 20 is about 4000 to 5000 mm, if the maximum width H2 is 10 mm or more, the positive electrode tab group, which is a bundle of positive electrode tabs 28, can be welded to the positive electrode current collector 5 (see FIG. 2) even if the positive electrode tab group is not aligned and shifted by the shift width L as shown in FIG. 5. This misalignment of the positive electrode tabs 28 is caused by an error from the design value of the thickness of the positive electrode plate 20, and if the maximum width H2 is equal to or greater than twice the misalignment width L, the positive electrode tab group and the positive electrode current collector 5 can be well welded. By making the root width H1 and the maximum width H2 satisfy the relationship 0.4×H2≦H1≦0.9×H2, it is possible to narrow the root width H1 while widening the maximum width H2, thereby making it possible to suppress the occurrence of cracks in the positive electrode core 22 while responding to an increase in battery capacity.

[0035] FIG. 4(b) is a diagram showing another example of the positive electrode tab 28, and shows a case where the angle α formed by the side of the positive electrode tab 28 and the side parallel to the longitudinal direction of the positive electrode core 22 at the intersection point of the side of the positive electrode tab 28 and the positive electrode core 22 at the base of the positive electrode tab 28 is an obtuse angle. The positive electrode tab 28 has a bilaterally symmetrical shape, and the positive electrode tab 28 has a constriction with a minimum width H3. Also, FIG. 4(c) shows a case where the angle α formed by the side of the positive electrode tab 28 and the side parallel to the longitudinal direction of the positive electrode core 22 at the intersection point of the side of the positive electrode tab 28 and the positive electrode core 22 at the base of the positive electrode tab 28 is a right angle. FIG. 4(d) and FIG. 4(e) show a case where the side of the positive electrode tab 28 connected to the positive electrode core 22 at the base of the positive electrode tab 28 is a curved line. In this case, the angle α is formed between the tangent to the side of the positive electrode tab 28 and the side parallel to the longitudinal direction of the positive electrode core 22 at the base of the positive electrode tab 28. Therefore, Fig. 4(d) shows a case where the angle α is an acute angle, and Fig. 4(e) shows a case where the angle α is an obtuse angle. Fig. 4(f) shows a case where the angle α formed between the tangent to the side of the positive electrode tab 28 and the side parallel to the longitudinal direction of the positive electrode core 22 at the base of the positive electrode tab 28 is a right angle, and a curve is included in part of the side that defines the width direction of the positive electrode tab 28.

[0036] When the angle α is an acute angle, the set root width H1 can be designed as the minimum width of the positive electrode tab 28. Since the resistance of the positive electrode tab 28 is determined by the minimum width of the positive electrode tab 28, a design can be made that minimizes the reduction in resistance due to the positive electrode tab 28 by optimally setting the root width H1. On the other hand, when the angle α is an obtuse angle, cracks occurring from the root of the positive electrode tab 28 in the longitudinal direction of the positive electrode core 22 are even less likely to occur.

[0037] The positive electrode tabs 28 do not need to have a symmetrical shape, but it is preferable that the positive electrode tabs 28 have a symmetrical shape in order to avoid uneven distribution of stress that occurs when the positive electrode active material layer 24 is compressed and to suppress cracks in the positive electrode core 22. In addition, the positive electrode tabs 28 may each have a different shape, but it is preferable that they have the same shape in order to be bundled together.

[0038] Next, a manufacturing method of the positive electrode plate 20 will be described. The manufacturing method of the positive electrode plate 20 includes a step of preparing a precursor of the positive electrode plate 20 and a step of compressing the precursor. First, a positive electrode active material slurry is applied in a strip shape to the surface of the positive electrode core 22, leaving a positive electrode active material layer uncoated portion 26, and then dried. Next, a precursor of the positive electrode plate 20 is prepared by cutting a metal foil so as to cut out a positive electrode tab 28 from the positive electrode active material layer uncoated portion 26. Thereafter, the positive electrode plate 20 can be manufactured by compressing the precursor of the positive electrode plate 20 with a roller or the like. When cutting out the positive electrode tab 28 from the positive electrode active material layer uncoated portion 26, a punching die, a cutter, an energy beam such as a laser beam, or the like can be used. Using an energy beam is preferable because it does not require frequent replacement work due to wear of the punching die or cutter.

[0039] [Negative electrode] The negative electrode plate 30 has a metallic negative electrode core 32 and a negative electrode active material layer 34 containing a negative electrode active material formed on the surface of the negative electrode core 32. The negative electrode core 32 can 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 thickness of the negative electrode core 32 is, for example, 5 to 15 μm.

[0040] The negative electrode active material layers 34 contain a negative electrode active material and a binder, and are preferably provided at corresponding positions on both sides of the negative electrode core 32. The negative electrode plate 30 can be produced by applying a negative electrode active material slurry containing a negative electrode active material, a binder, and the like onto the negative electrode core 32, drying the coating, and then compressing it with a roller or the like to form the negative electrode active material layers 34 on both sides of the negative electrode core 32.

[0041] 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 active material layer 34 may also contain a lithium titanium composite oxide.

[0042] A known binder can be used for the binder contained in the negative electrode active material 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 active material 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).

[0043] The negative electrode tab 38 extends in the short direction of the negative electrode core 32 from a negative electrode active material layer uncoated portion 36 on the surface of the negative electrode core 32 where the negative electrode active material layer 34 is not formed. 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 negative electrode tab 38 in the longitudinal direction of the negative electrode core 32 is adjusted so as to be aligned when wound. In this embodiment, the negative electrode core 32 extends to form the negative electrode tab 38. Specifically, the negative electrode core 32 with the negative electrode tab 38 is produced by cutting a metal foil into a shape in which the negative electrode tab 38 is connected to the negative electrode core 32.

[0044] The negative electrode tab 38 may have a narrow base width, similar to the positive electrode tab 28. When the negative electrode active material layer 34 is densified, problems similar to those of the positive electrode plate 20 arise, so the base width H1 and maximum width H2 of the negative electrode tab 38 may satisfy the relationship 0.4×H2≦H1≦0.9×H2. The shape of the negative electrode tab 38 may be the same as or different from the shape of the positive electrode tab 28.

[0045] [Separator] 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.

[0046] The present embodiment will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0047] <Example 1> [Preparation of positive electrode plate] Lithium nickel cobalt manganese oxide as a positive electrode active material, 2% by mass of carbon black relative to the positive electrode active material, and 1% by mass of polyvinylidene fluoride (PVdF) relative to the positive electrode active material were mixed, and then N-methyl-2-pyrrolidone (NMP) was added and stirred using a mixer (TK Hivismix, manufactured by Primix Corporation) to prepare a positive electrode active material slurry. The positive electrode active material slurry was then applied in strips to corresponding positions on both sides of a positive electrode core made of aluminum foil with a thickness of 13 μm so as to form positive electrode active material layer uncoated portions 26, and then dried.

[0048] A positive electrode core with a positive electrode tab was produced by cutting the positive electrode active material layer uncoated portion 26 using a laser beam so that the positive electrode tab extended from the positive electrode core. The positive electrode tab had a shape as shown in FIG. 4(a), with a base width H1 of 12 mm and a maximum width H2 of 30 mm. The length of the positive electrode core was 4750 mm, the width of the positive electrode active material layer uncoated portion was 1 mm, and two groups of positive electrode tabs each consisting of 17 positive electrode tabs were provided. The distance between the positive electrode tabs was designed based on a state in which the thickness was 4 μm thinner than the thickness of the positive electrode plate expected after compression, and the positive electrode plate was intentionally shifted.

[0049] The positive electrode precursor was then compressed with a roller. The thickness of the region where the positive electrode active material layer was the surface was 180 μm before compression and 136 μm after compression. The packing density of the positive electrode active material layer after compression was 3.5 g / cm 3 It was.

[0050] [Preparation of negative electrode plate] Graphite was used as the negative electrode active material, and 1% by mass of styrene butadiene rubber (SBR) relative to the negative electrode active material and 1% by mass of carboxymethyl cellulose relative to the negative electrode active material were mixed, and water was added and stirred using a mixer (TK Hivismix, manufactured by Primix Corporation) to prepare a negative electrode active material slurry. The negative electrode active material slurry was applied in a strip shape to the corresponding positions on both sides of the negative electrode core, and then dried and compressed with a roller. A negative electrode core with a negative electrode tab was produced by cutting a copper foil with a thickness of 8 μm into a shape in which the negative electrode tab extended from the negative electrode core. The shape of the negative electrode tab was the same as that of the positive electrode tab. The length of the negative electrode core was 5073 mm, the width of the portion not coated with the negative electrode active material layer was 0 mm, and the position of the negative electrode tab was designed so that two sets of negative electrode tab groups consisting of 18 negative electrode tabs were provided. In this way, a negative electrode plate with a thickness of 160 μm in which a negative electrode active material layer was formed on both sides of the negative electrode core was produced.

[0051] [Preparation of electrode body] The positive and negative electrode plates were wound with a 16 μm-thick polyethylene microporous membrane separator interposed therebetween, and then press-molded to produce a flat wound electrode body.

[0052] <Example 2, Comparative Examples 1 to 3> For Example 2 and Comparative Examples 1 to 3, positive electrode plates, negative electrode plates, and electrode assemblies were produced in the same manner as in Example 1, except that the base width H1 and maximum width H2 were changed as shown in Table 1.

[0053] [Evaluation of crack occurrence] Before preparing the electrode body, the positive electrode plate was visually observed to evaluate whether or not cracks had occurred starting from the base of the tab. If a crack was confirmed, it was rated as "present", and otherwise it was rated as "absent".

[0054] [Weldability evaluation] In the produced electrode assembly, the deviation width L of the positive electrode tab was 7 mm. When the maximum width H2 was twice or more the deviation width L of the positive electrode tab, that is, when the maximum width H2 was 14 mm or more, it was rated as "good", and otherwise it was rated as "poor".

[0055] The evaluation results for each of the examples and comparative examples are shown in Table 1.

[0056] [Table 1]

[0057] As can be seen from Table 1, it was confirmed that when the root width H1 and maximum width H2 of the positive electrode tab satisfy the relationship 0.4×H2≦H1≦0.9×H2, the occurrence of cracks can be suppressed while ensuring weldability. [Explanation of symbols]

[0058] 1 Exterior body 2 Sealing plate 3 Electrode body 4 Positive terminal 5 Positive electrode current collector 6 Negative terminal 7 Negative terminal 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 Cathode active material layer 26 Positive electrode active material layer uncoated area 28 Positive tab 30 Negative plate 32 Negative electrode core 34 Negative electrode active material layer 36 Uncoated area of ​​negative electrode active material layer 38 Negative tab 40 Separator 100 Nonaqueous electrolyte secondary battery

Claims

1. A plate included in a wound electrode body, A strip-shaped electrode plate core body, an active material layer formed in a band shape on at least a part of a surface of the electrode plate core along the longitudinal direction of the electrode plate core; a tab extending in a lateral direction of the electrode plate core from an active material layer uncoated portion of the surface of the electrode plate core on which the active material layer is not formed, a base width H1 and a maximum width H2 of the tab satisfy the relationship 0.4×H2≦H1≦0.9×H2, The tab has a base width H1 of 15 mm or less, An electrode plate, wherein at a base of the tab, an angle formed by a side of the tab and a side of the electrode plate core parallel to a longitudinal direction thereof at an intersection between the side of the tab and the electrode plate core is an acute angle.

2. The electrode plate according to claim 1 , wherein the tab has a root width H1 of 12 mm or less.

3. The packing density of the active material layer is 3.5 g / cm ３ The electrode plate according to claim 1 or 2.

4. The electrode plate according to any one of claims 1 to 3, wherein the electrode plate is a positive electrode plate.

5. 5. A non-aqueous electrolyte secondary battery comprising: a wound electrode assembly including the electrode plate according to claim 1; and a battery case housing the electrode assembly.

6. A method for manufacturing an electrode plate included in a wound electrode body, comprising the steps of: a step of preparing a precursor of an electrode plate, the precursor having a strip-shaped electrode plate core, an active material slurry applied in a strip shape to at least a part of a surface of the electrode plate core along the longitudinal direction of the electrode plate core, and a tab extending in a lateral direction of the electrode plate core from an active material layer unapplied part of the surface of the electrode plate core where the active material slurry is not applied, wherein a base width H1 and a maximum width H2 of the tab satisfy a relationship of 0.4×H2≦H1≦0.9×H2, the base width H1 of the tab is 15 mm or less, and an angle formed by a side of the tab and a side parallel to the longitudinal direction of the electrode plate core at an intersection of the side of the tab and the electrode plate core at the base of the tab is an acute angle; and compressing the precursor.

7. The method for manufacturing an electrode plate according to claim 6 , wherein the step of preparing a precursor of the electrode plate includes a step of forming the tab by processing the portion not coated with the active material layer using an energy beam.

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