Method for manufacturing battery, electrode, electrode body, and battery

Abstract

The invention discloses a battery manufacturing method, an electrode, an electrode body and a battery. A method for manufacturing a battery provided with an electrode including a current collector and an electrode layer disposed on the current collector, the method including a first step of forming the electrode layer on the current collector and a second step of forming a trench in the surface of the electrode layer, the trench is formed by removing a portion of the electrode layer by laser irradiation.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a battery, an electrode, an electrode body, and a battery. Background Art

[0002] In the manufacturing process of a battery using an electrolytic solution obtained by dissolving an electrolyte in an organic solvent, a liquid injection operation is performed to supply the electrolytic solution into an outer casing that houses an electrode body and allow the electrolytic solution to penetrate into the electrode body.

[0003] The electrodes of the battery are sometimes pressed at high pressure to increase the energy density. If the packing density of the electrode active material in the electrode is increased by pressing the electrode, the permeability of the electrolyte is reduced. The reduction in the permeability of the electrolyte becomes a cause of the reduction in the efficiency of the injection operation and the reduction in the production efficiency of the battery.

[0004] As a method of shortening the time required for the electrolyte injection operation into the electrode assembly, Patent Document 1 discloses, for example, providing a slit in a separator disposed between a positive electrode and a negative electrode.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2001-068085 Summary of the invention

[0008] When the electrode body is manufactured by laminating electrodes with a separator having slits disposed therebetween as in the method described in Patent Document 1, the density of the electrodes in the electrode body after pressing may not be sufficiently uniform.

[0009] An object of one embodiment of the present disclosure is to provide a novel method for manufacturing a battery, an electrode, an electrode body, and a battery that are excellent in electrolyte permeability and can maintain a good energy density.

[0010] Means for solving the above-mentioned problems include the following embodiments.

[0011] <1> A method for manufacturing a battery is a method for manufacturing a battery having the following electrode, wherein the electrode comprises a current collector and an electrode layer disposed on the current collector, the manufacturing method comprising:

[0012] A first step of forming an electrode layer on the current collector; and

[0013] a second step of forming grooves on the surface of the electrode layer,

[0014] The groove is formed by removing a portion of the electrode layer by laser irradiation.

[0015] <2> according to <1> In the battery manufacturing method, the density of the portion of the electrode layer corresponding to the lower portion of the groove is equal to the density of the portion of the electrode layer without the groove.

[0016] <3> An electrode comprises a current collector and an electrode layer arranged on the current collector.

[0017] The electrode layer has grooves on the surface,

[0018] The density of the portion of the electrode layer corresponding to the lower portion of the groove is equal to the density of the portion of the electrode layer not having the groove.

[0019] <4> An electrode body having <3> The electrode.

[0020] <5> A battery having <3> The electrode.

[0021] According to one embodiment of the present disclosure, it is possible to provide a novel method for manufacturing a battery, an electrode, an electrode body, and a battery that are excellent in electrolyte permeability and can maintain a good energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram schematically showing an example of the structure of an electrode body.

[0023] Figure 2 This is a diagram schematically showing an example in which a battery module is applied to an electric vehicle.

[0024] Figure 3 This is a diagram schematically showing an example of the configuration of a battery module.

[0025] Figure 4 This is a diagram schematically showing an example of the configuration of a battery module.

[0026] Figure 5 This is a diagram schematically showing an example of the configuration of battery cells included in a battery module. DETAILED DESCRIPTION

[0027] In the present disclosure, a numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the minimum value and the maximum value, respectively.

[0028] In the numerical ranges recorded in stages in the present disclosure, the upper limit or lower limit recorded in a certain numerical range can be replaced by the upper limit or lower limit of other numerical ranges recorded in stages. In the numerical ranges recorded in the present disclosure, the upper limit or lower limit recorded in a certain numerical range can be replaced by the value shown in the embodiment.

[0029] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0030] In the present disclosure, when an embodiment is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the sizes of components in each figure are conceptual, and the relative relationship between the sizes of the components is not limited to this.

[0031] <Battery Manufacturing Method>

[0032] The manufacturing method of the battery disclosed in the present invention is a manufacturing method of a battery having the following electrode, wherein the electrode comprises a current collector and an electrode layer disposed on the current collector, and the manufacturing method comprises:

[0033] A first step of forming an electrode layer on the current collector; and

[0034] a second step of forming grooves on the surface of the electrode layer,

[0035] The groove is formed by removing a portion of the electrode layer by laser irradiation.

[0036] In the method of the present disclosure, a portion of the electrode layer is removed by laser irradiation, thereby forming grooves on the surface of the electrode layer.

[0037] The grooves formed in the electrode layer serve as migration paths for the electrolyte in the surface direction of the electrode layer, for example, and play a role in promoting the penetration of the electrolyte into the electrode.

[0038] As a method for forming grooves in the electrode layer, there is a method in which a region where the electrode layer is formed and a region where the electrode layer is not formed are arranged in a pattern on the current collector, and the region where the electrode layer is not formed is used as the groove.

[0039] However, in the above method, since the electrode layer containing the active material does not exist in the portion corresponding to the groove, the energy density of the electrode may be reduced.

[0040] In the method of forming the groove by laser irradiation, the depth of the groove can be easily controlled to be smaller than the thickness of the electrode layer, and the active material can also be present in the region of the electrode layer corresponding to the groove. Therefore, the reduction in energy density caused by the formation of the groove can be suppressed.

[0041] As another method of forming a groove in the electrode layer, there is a method of pressurizing a region of the electrode layer corresponding to the groove to form a recessed portion, and utilizing the recessed portion as the groove.

[0042] However, in the above method, the density of the groove forming region of the electrode layer becomes higher than the designed value, and the permeability of the electrolyte may be reduced.

[0043] In the method of the present disclosure for forming grooves by laser irradiation, the grooves are formed by removing a portion of the electrode layer. Thus, the density of the region of the electrode layer corresponding to the grooves is not too high, and the permeability of the electrolyte is well maintained. In addition, a uniform density of the electrode layer regardless of the presence or absence of grooves is advantageous in achieving good battery performance.

[0044] A battery manufactured by the method disclosed herein includes an electrode including a current collector and an electrode layer disposed on the current collector, wherein at least a portion of the electrode has grooves formed in the electrode layer.

[0045] All electrodes included in the battery may have grooves formed in the electrode layer, or a part of electrodes included in the battery may have grooves formed in the electrode layer.

[0046] For example, when one of the negative electrode and the positive electrode included in the battery has a groove formed in the electrode layer, the other may or may not have a groove formed in the electrode layer.

[0047] Generally, the negative electrode has more spaces between active material particles than the positive electrode and has better permeability to the electrolyte. Therefore, the negative electrode may also have grooves formed in the electrode layer.

[0048] (1st step)

[0049] In the first step, an electrode layer is formed on the current collector.

[0050] The method for forming the electrode layer on the current collector is not particularly limited and can be selected from known methods. For example, the electrode layer can be formed by coating a composition containing the components contained in the electrode layer on the current collector. As the components contained in the electrode layer, electrode active materials, conductive materials, adhesives, etc. can be cited.

[0051] When the battery is a lithium ion secondary battery, the positive electrode active material may be a composite oxide composed of lithium and a transition metal and other metals that may be optionally contained (hereinafter also referred to as a lithium transition metal composite oxide). As transition metals and other metals, Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. may be mentioned.

[0052] Examples of the lithium transition metal composite oxide include layered lithium transition metal composite oxides, spinel lithium transition metal composite oxides, and olivine lithium transition metal composite oxides.

[0053] Examples of the layered lithium transition metal composite oxide include layered lithium transition metal composite oxides containing at least one selected from Ni, Co and Mn as a transition metal. Specifically, examples include LiNi a Co b Mn c A compound represented by the structural formula O2 (a, b, c are respectively numbers greater than 0 and less than 1, a+b+c=1), and a compound obtained by adding one or more elements selected from Al, Mg, La, Ti, Zn, B, W, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au, Si, etc. to the above compound.

[0054] Specific examples of spinel-type lithium transition metal composite oxides include LiMn 2 O 4 .

[0055] Specific examples of the olivine-type lithium transition metal composite oxide include LiMPO 4 (M: Fe, Co, Ni, or Mn).

[0056] The positive electrode active material contained in the electrode layer may be a single type or two or more types.

[0057] When the battery is a lithium ion secondary battery, specific examples of the negative electrode active material include carbon materials such as graphite, hard carbon, soft carbon, and activated carbon, silicon, metallic lithium, lithium alloys, and lithium titanate (LTO).

[0058] The negative electrode active material contained in the electrode layer may be a single type or two or more types.

[0059] Specific examples of the conductive material include carbon materials such as carbon black (acetylene black, thermal black, furnace black, etc.), carbon nanotubes, and graphite.

[0060] The conductive material contained in the electrode layer may be a single type or two or more types.

[0061] Specific examples of binders include polyvinylidene fluoride (PVdF), polyethylene, polypropylene, polyethylene terephthalate, cellulose, nitrocellulose, carboxymethyl cellulose, polyethylene oxide, polyepichlorohydrin, polyacrylonitrile, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), polyacrylate, polymethacrylate, polytetrafluoroethylene (PTFE), and the like.

[0062] The binder contained in the electrode layer may be a single type or two or more types.

[0063] Examples of the material of the current collector constituting the positive electrode include aluminum, aluminum alloys, nickel, titanium, stainless steel, etc. Examples of the shape of the current collector include foil, mesh, and the like.

[0064] Examples of the material of the current collector constituting the negative electrode include copper, copper alloys, nickel, titanium, stainless steel, etc. Examples of the shape of the current collector include foil, mesh, and the like.

[0065] (Second step)

[0066] In the second step, a groove is formed on the surface of the electrode layer formed in the first step. The groove is formed by removing a part of the electrode layer by laser irradiation.

[0067] The type of laser used for forming the groove is not particularly limited, and a known laser can be used.

[0068] Specific examples of the laser include solid lasers such as YAG lasers, fiber lasers, and semiconductor lasers, and gas lasers such as carbon dioxide lasers, excimer lasers, and He—Ne lasers.

[0069] The electrolyte solution mainly permeates the electrode layer from the end surface (cut surface) of the electrode layer. Therefore, from the viewpoint of promoting the permeation of the electrolyte solution, it is preferable that the end of the groove formed in the electrode layer is located at the end surface of the electrode layer.

[0070] From the viewpoint of further promoting the penetration of the electrolyte, the direction of the grooves formed in the electrode layer is preferably along the flow direction of the electrolyte when the electrolyte penetrates into the electrode.

[0071] The depth of the groove formed in the electrode layer is not particularly limited and can be selected according to the shape of the battery, the thickness of the electrode layer, and the like.

[0072] The depth of the groove formed in the electrode layer can be selected from a range of, for example, 10% to 90% of the thickness of the electrode layer.

[0073] The thickness of the electrode layer is not particularly limited and can be selected from the thickness of common electrode layers. For example, the thickness of the electrode layer can be selected from the range of 10 μm to 200 μm.

[0074] The number of grooves formed in the electrode layer may be one or more.

[0075] The grooves formed in the electrode layer may be arranged in a stripe shape, a lattice shape, or a dendrite shape (a structure consisting of a trunk and branches).

[0076] From the viewpoint of maintaining good electrolyte permeability and achieving good battery performance, the density of the portion of the electrode layer corresponding to the lower portion of the groove is preferably equal to the density of the portion of the electrode layer without the groove.

[0077] The electrode having grooves formed on the surface of the electrode layer can constitute an electrode body.

[0078] In the present disclosure, the electrode body means a structure including a stacked body composed of a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

[0079] Examples of the form of the electrode body including a stack composed of a positive electrode, a negative electrode, and a separator disposed therebetween include a stack of multiple stacks cut into predetermined sizes and a wound stack.

[0080] Examples of the separator included in the electrode body include nonwoven fabrics, cloths, and microporous films mainly composed of polyolefins such as polyethylene and polypropylene.

[0081] exist Figure 1 An example of the structure of the stacked body included in the electrode body is schematically shown in FIG.

[0082] Figure 1 The laminate 100 shown is composed of a positive electrode 10, a negative electrode 20, and a separator 30 disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10 is composed of a positive electrode layer 10A and a positive electrode collector 10B. The negative electrode 20 is composed of a negative electrode layer 20A and a negative electrode collector 20B.

[0083] The electrode assembly is housed in the outer casing of the battery.

[0084] The type of the outer casing that houses the electrode assembly is not particularly limited and can be selected according to the type of the battery.

[0085] In one embodiment, a sheet-shaped outer casing may be used.

[0086] As a sheet-like outer casing, an outer casing containing metal can be cited. Specifically, a laminate (so-called laminate film) having a metal layer containing a metal such as aluminum and a heat seal layer (heat seal layer) containing a resin melted by heating can be cited. That is, the battery manufactured by the method disclosed herein can be a battery using a laminate film as an outer casing (so-called laminate battery).

[0087] The outer casing may be a single member or may be composed of two or more members. For example, when the outer casing is a sheet-like object, the outer casing may be composed of a single sheet-like object or may be composed of two sheet-like objects.

[0088] If necessary, the recessed portion for accommodating the electrode body may be formed in the sheet-like outer casing by embossing.

[0089] As a method of housing the electrode assembly in an outer casing using a sheet-like outer casing, for example, the following method 1 and method 2 can be cited.

[0090] Method 1: A method in which the outer casing around the electrode assembly is joined in a state in which the electrode assembly is disposed between one outer casing folded in half or between two overlapping outer casings.

[0091] Method 2: A method in which a bag is prepared by joining the peripheries of a single outer casing folded in half or two overlapping outer casings, and the electrode assembly is placed in the bag.

[0092] The battery is obtained by allowing the electrolyte solution to permeate the electrode assembly housed in the outer casing.

[0093] As the electrolyte solution, an electrolyte solution obtained by dissolving an electrolyte such as LiPF 6 or LiFSi in a solvent can be used without particular limitation.

[0094] As the solvent, specifically, cyclic or chain carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) can be mentioned. The solvent can also be a mixture of two or more solvents, or a mixture comprising cyclic carbonates and chain carbonates.

[0095] The solvent may contain additives such as vinylene carbonate (VC).

[0096] <Electrode>

[0097] The electrode disclosed in the present invention comprises a current collector and an electrode layer disposed on the current collector.

[0098] The electrode layer has grooves on the surface,

[0099] The density of the portion of the electrode layer corresponding to the lower portion of the groove is equal to the density of the portion of the electrode layer not having the groove.

[0100] The electrode disclosed in the present invention has grooves on the surface of the electrode layer. The grooves serve as migration paths for the electrolyte in the surface direction of the electrode layer, for example, and play a role in promoting the penetration of the electrolyte into the electrode.

[0101] In the electrode disclosed herein, the density of the portion of the electrode layer corresponding to the lower portion of the groove is equal to the density of the portion of the electrode layer without the groove. Therefore, the density of the portion of the electrode layer corresponding to the groove is not too high, and the permeability of the electrolyte is well maintained. In addition, good battery performance can be achieved by uniform density of the electrode layer. Moreover, since active material is also present in the portion of the electrode layer where the groove is formed, the reduction in energy density of the electrode caused by the formation of the groove is small.

[0102] In the electrode of the present disclosure, a state in which the density of the portion of the electrode layer corresponding to the lower portion of the groove is equal to the density of the portion of the electrode layer without the groove can be created by, for example, removing a portion of the electrode layer in the region where the groove is formed.

[0103] The method of removing a portion of the electrode layer in the region where the groove is formed is not particularly limited, but laser irradiation is preferred from the viewpoint of accurately forming a groove of a desired size. Whether the groove is formed by laser irradiation can be determined based on the surface state of the groove and other traces.

[0104] The details and preferred embodiments of the electrode of the present disclosure are the same as the details and preferred embodiments of the electrode in the above-mentioned method for producing a battery.

[0105] <Electrode body>

[0106] The electrode body of the present disclosure includes the above-mentioned electrode of the present disclosure.

[0107] The details and preferred embodiments of the electrode body of the present disclosure are the same as the details and preferred embodiments of the electrode body in the above-mentioned method of manufacturing a battery.

[0108] <Battery>

[0109] The battery of the present disclosure includes the electrode of the present disclosure described above. The battery of the present disclosure may be a battery manufactured by the method for manufacturing the battery of the present disclosure described above.

[0110] The type of battery is not particularly limited.

[0111] Specific examples of the battery include secondary batteries such as lithium ion secondary batteries, lead storage batteries, nickel-metal hydride storage batteries, nickel-cadmium storage batteries, nickel-iron storage batteries, nickel-zinc storage batteries, silver oxide-zinc storage batteries, and cobalt-titanium-lithium secondary batteries.

[0112] From the viewpoint of energy density, versatility, etc., the battery may be a lithium ion secondary battery.

[0113] The battery of the present disclosure can be mounted on an electric vehicle. Hereinafter, an example of applying the battery of the present disclosure to an electric vehicle will be described with reference to the accompanying drawings. In the following description, "battery unit 20" corresponds to the battery of the present disclosure.

[0114] Figure 2 1 is a schematic plan view showing the main parts of a vehicle 100 to which the battery pack 10 according to the embodiment is applied. Figure 2 As shown, the vehicle 100 is an electric vehicle (BEV) equipped with a battery pack 10 under the floor. In addition, the arrows UP, FR, and LH in each figure respectively indicate the upper side in the vehicle vertical direction, the front side in the vehicle front-back direction, and the left side in the vehicle width direction. When the front-back, left-right, up-down and down directions are used for explanation, unless otherwise specified, they indicate the front-back in the vehicle front-back direction, the left-right in the vehicle width direction, and the up-down in the vehicle vertical direction.

[0115] The vehicle 100 of the present embodiment, as an example, is provided with a DC / DC converter 102, an electric compressor 104, and a PTC (Positive Temperature Coefficient) heater 106 on the vehicle front side relative to the battery pack 10. In addition, an electric motor 108, a gear box 110, an inverter 112, and a charger 114 are provided on the vehicle rear side relative to the battery pack 10.

[0116] The DC current output from battery pack 10 is regulated in voltage by DC / DC converter 102 and then supplied to electric compressor 104, PTC heater 106, inverter 112, etc. Furthermore, by supplying power to electric motor 108 via inverter 112, the rear wheels rotate and vehicle 100 travels.

[0117] A charging port 116 is provided at the right side of the rear portion of the vehicle 100 . By connecting a charging plug of an external charging device (not shown) to the charging port 116 , electricity can be stored in the battery pack 10 via the charger 114 .

[0118] The configuration and structure of each component constituting the vehicle 100 are not limited to the above-mentioned configuration. For example, it can also be applied to a hybrid vehicle (HV: Hybrid Vehicle) or a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle) equipped with an engine. In addition, in the present embodiment, the motor 108 is mounted on the rear of the vehicle and is a rear-wheel drive vehicle, but it is not limited to this. The motor 108 can also be mounted on the front of the vehicle. A front-wheel drive vehicle can also be mounted on the front and rear of the vehicle. In addition, it can also be a vehicle with an in-wheel motor on each wheel.

[0119] The battery pack 10 is composed of a plurality of battery modules 11. In the present embodiment, as an example, 10 battery modules 11 are provided. Specifically, five battery modules 11 are arranged in the vehicle front-rear direction on the right side of the vehicle 100, and five battery modules 11 are arranged in the vehicle front-rear direction on the left side of the vehicle 100. In addition, each battery module 11 is electrically connected.

[0120] Figure 3 1 is a schematic three-dimensional diagram of the battery module 11. Figure 3 As shown, the battery module 11 is formed into a substantially rectangular parallelepiped shape with the vehicle width direction as the length direction. In addition, the outer shell of the battery module 11 is formed of an aluminum alloy. For example, the outer shell of the battery module 11 is formed by joining aluminum die castings at both ends of an aluminum alloy extrusion material by laser welding or the like.

[0121] A pair of voltage terminals 12 and a connector 14 are provided at both ends of the battery module 11 in the vehicle width direction. A flexible printed circuit board 21 described later is connected to the connector 14. In addition, bus bars (not shown) are welded to both ends of the battery module 11 in the vehicle width direction.

[0122] The battery module 11 has a length MW in the vehicle width direction of, for example, 350 mm to 600 mm, a length ML in the vehicle front-rear direction of, for example, 150 mm to 250 mm, and a height MH in the vehicle up-down direction of, for example, 80 mm to 110 mm.

[0123] Figure 4 1 is a plan view of a state where the upper cover of the battery module 11 is removed. Figure 4 As shown, a plurality of battery cells 20 are housed in an aligned state inside the battery module 11. In the present embodiment, as an example, 24 battery cells 20 are aligned in the vehicle front-rear direction and bonded to each other.

[0124] A flexible printed circuit (FPC) board 21 is disposed on the battery cell 20. The flexible printed circuit board 21 is formed in a strip shape with the vehicle width direction as the longitudinal direction, and thermistors 23 are provided at both ends of the flexible printed circuit board 21. The thermistor 23 is not bonded to the battery cell 20 but is pressed toward the battery cell 20 by the upper cover of the battery module 11.

[0125] In addition, one or more buffer materials (not shown) are accommodated inside the battery module 11. For example, the buffer material is a thin plate-shaped member that can be elastically deformed, and is arranged between adjacent battery cells 20 with the arrangement direction of the battery cells 20 as the thickness direction. In this embodiment, as an example, buffer materials are respectively arranged at both ends in the longitudinal direction and the central part in the longitudinal direction of the battery module 11.

[0126] Figure 5 2 is a schematic diagram of a battery cell 20 housed in a battery module 11 as viewed from the thickness direction. Figure 5 As shown, the battery cell 20 is formed in a substantially rectangular plate shape, and an electrode body (not shown) is accommodated therein. The electrode body is formed by stacking a positive electrode, a negative electrode, and a separator, and is sealed by a laminate film 22 .

[0127] In this embodiment, as an example, the electrode body receiving portion is formed by folding and laminating the embossed sheet-shaped laminate film 22. The laminate film 22 can have any one of a single cup embossed structure with one embossing and a double cup embossed structure with two embossings. The laminate film 22 in one embodiment has a single cup embossed structure with a drawing depth of about 8 mm to 10 mm.

[0128] The upper ends of both ends of the battery cell 20 in the longitudinal direction are bent, and the corners become the outer shape. In addition, the upper end of the battery cell 20 is bent, and a fixing tape 24 is wound around the upper end of the battery cell 20 along the longitudinal direction.

[0129] Terminals (tabs) 26 are provided at both ends of the battery cell 20 in the longitudinal direction. In the present embodiment, as an example, the terminals 26 are provided at positions offset downward from the vertical center of the battery cell 20. The terminals 26 are joined to bus bars (not shown) by laser welding or the like.

[0130] For example, the length CW1 of the battery cell 20 in the vehicle width direction is 530mm~600mm, 600mm~700mm, 700mm~800mm, 800mm~900mm, or 1000mm or more, the length CW2 of the area accommodating the electrode body is 500mm~520mm, 600mm~700mm, 700mm~800mm, 800mm~900mm, or 1000mm or more, the height CH is 80mm~110mm, or 110mm~140mm, the thickness is 5.0mm~7.0mm, 7.0mm~9.0mm, or 9.0mm~11.0mm, and the height TH of the terminal 26 is 40mm~50mm, 50mm~60mm, or 60mm~70mm.

Claims

1. A method for manufacturing a battery, comprising: A first step of forming an electrode layer on the current collector; and a second step of forming grooves on the surface of the electrode layer, The groove is formed by removing a portion of the electrode layer by laser irradiation.

2. The method for manufacturing a battery according to claim 1, The density of the portion of the electrode layer corresponding to the lower portion of the groove is equal to the density of the portion of the electrode layer not having the groove.

3. An electrode comprising a current collector and an electrode layer disposed on the current collector, The electrode layer has grooves on the surface, The density of the portion of the electrode layer corresponding to the lower portion of the groove is equal to the density of the portion of the electrode layer not having the groove. An electrode body comprising the electrode according to claim 3.

5. A battery comprising the electrode according to claim 3.

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