Anode electrode sheet, electrochemical device and electronic device

Abstract

Provided are an anode electrode sheet, an electrochemical device and an electronic device, which relate to the field of batteries. The anode electrode sheet is bent in a first direction X, the anode electrode sheet comprising an outer arc anode material layer, an anode current collector and an inner arc anode material layer which are arranged in sequence in the first direction X, wherein the outer arc anode material layer comprises a first anode material layer and a second anode material layer, the second anode material layer being arranged between the first anode material layer and the anode current collector; the first anode material layer contains graphite, and the second anode material layer and the inner arc anode material layer both contain hard carbon. The anode electrode sheet of the described structure can reduce arc rebound in a battery cell, improving the safety and reliability of the battery cell.

Description

Anode plate, electrochemical device and electronic device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an anode electrode, an electrochemical device, and an electronic device. Background Art

[0002] With the increasing diversity of consumer electronics applications, especially the development of virtual reality technology, the demand for battery cells compatible with head-mounted electronic devices is becoming increasingly urgent. Many well-known domestic and international companies have entered this field and have successfully launched a number of head-mounted virtual reality electronic devices. Because the battery cells in these head-mounted electronic devices need to match the terminal battery compartment, they are typically designed with a curved shape. However, these curved cells can experience arc rebound during manufacturing and consumer use, which can easily lead to black spots on the outer layer of the cell, affecting the safety and reliability of the cell.

[0003] Summary of the Invention

[0004] In view of the above problems, the present application provides an anode electrode, an electrochemical device and an electronic device, which can reduce the curvature rebound phenomenon of the battery cell and improve the safety and reliability of the battery cell.

[0005] In a first aspect, the present application provides an anode electrode sheet, the anode electrode sheet being bent in a first direction X, the anode electrode sheet comprising an outer arc anode material layer, an anode current collector, and an inner arc anode material layer sequentially arranged along the first direction X, the outer arc anode material layer comprising a first anode material layer and a second anode material layer, the second anode material layer being arranged between the first anode material layer and the anode current collector;

[0006] The first anode material layer includes graphite, and the second anode material layer and the inner arc anode material layer both include hard carbon.

[0007] In the technical solution of the embodiment of the present application, the anode pole piece is curved, the outer arc anode material layer is arranged in layers using different carbon-based materials, and the inner arc anode material layer is also designed with a different carbon-based material relative to the outer arc anode material layer: the first anode material layer close to the outer arc side of the outer arc anode material layer contains graphite, which can be designed as an anode material layer with large rebound, the second anode material layer close to the inner arc side contains hard carbon, which can be designed as an anode material layer with small rebound, and the inner arc anode material layer contains hard carbon, which can be designed as an anode material layer with small rebound. The anode pole piece adopts a rebound difference design, so that during the use of the arc-shaped battery cell, along the plane direction of the anode pole piece, the first anode material layer with large rebound generates shear stress on the second anode material layer and the inner arc anode material layer with small rebound, which can reduce the arc rebound phenomenon. At the same time, along the thickness direction of the anode pole piece, the first anode material layer with large rebound can also supplement the outer arc space to reduce the slip and spacing between the pole pieces, thereby improving the safety and reliability of the battery.

[0008] In any one or more optional embodiments above, the median particle size Dv50 of the graphite is 10 to 20 μm, and the median particle size Dv50 of the hard carbon is 2 to 10 μm.

[0009] In any one or more of the above optional embodiments, the graphite powder compaction density is 1.5 to 2.0 g / cm 3 The compacted density of the hard carbon powder is 0.5 to 1.5 g / cm 3 .

[0010] In any one or more optional embodiments above, the anode plate satisfies at least one of the following conditions:

[0011] (1) The first anode material layer includes a binder, and based on the mass of the first anode material layer, the mass percentage of the graphite is 96-98%, and the mass percentage of the binder is 1-2%; (2) The second anode material layer includes a binder, and based on the mass of the second anode material layer, the mass percentage of the hard carbon is 96-98%, and the mass percentage of the binder is 1-2%; (3) The inner arc anode material layer includes a binder, and based on the mass of the inner arc anode material layer, the mass percentage of the hard carbon is 96-98%, and the mass percentage of the binder is 1-2%.

[0012] In the technical solution of the embodiment of the present application, by adopting specific formulations for different anode material layers, the rebound difference control between the outer arc anode material layer and the inner arc anode material layer of the anode pole piece can be achieved.

[0013] In any one or more optional embodiments above, the first anode material layer, the second anode material layer and the inner arc anode material layer all include a binder, and the binders of the first anode material layer, the second anode material layer and the inner arc anode material layer are independently selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, alginic acid and sodium alginate.

[0014] In any one or more of the above optional embodiments, the relationship between the thickness a1 of the first anode material layer and the thickness A of the outer arc anode material layer satisfies a1: A = 0.25-0.75. In the outer arc anode material layer of the anode plate, the greater the proportion of the thickness of the first anode material layer with large rebound, the more conducive it is to reducing the curvature rebound of the anode plate; and the smaller the proportion of the thickness of the first anode material layer with large rebound, the more conducive it is to improving the energy density of the anode plate.

[0015] In any one or more optional embodiments above, the relationship between the thickness a1 of the first anode material layer and the thickness A of the outer arc anode material layer satisfies a1: A=0.4-0.6.

[0016] In any one or more of the above optional embodiments, the relationship between the thickness A of the outer arc anode material layer and the thickness B of the inner arc anode material layer satisfies B≤A≤2B. In the anode plate, a larger ratio of the thickness of the outer arc anode material layer to the thickness of the inner arc anode material layer is more conducive to reducing the curvature rebound of the anode plate; and a smaller ratio of the thickness of the outer arc anode material layer to the thickness of the inner arc anode material layer is more conducive to improving the energy density of the anode plate.

[0017] In any one or more optional embodiments above, a relationship between a thickness A of the outer arc anode material layer and a thickness B of the inner arc anode material layer satisfies 1.3B≤A≤1.7B.

[0018] In a second aspect, the present application provides an electrochemical device, which includes the anode electrode of the aforementioned embodiment.

[0019] In a third aspect, the present application provides an electronic device, which includes the electrochemical device of the aforementioned embodiment.

[0020] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0022] FIG1 is a schematic structural diagram of an anode electrode provided in an embodiment of the present application.

[0023] Icon: 1110 - anode plate; 1111 - first anode material layer; 1112 - second anode material layer; 1113 - anode current collector; 1114 - inner arc anode material layer. DETAILED DESCRIPTION

[0024] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0026] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0027] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0029] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "thickness", "up", "down", "inside", and "outside" is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the embodiments of the present application.

[0030] In the description of the embodiments of this application, unless otherwise expressly specified or limited, technical terms such as "installation," "connection," and "fixation" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on specific circumstances.

[0031] At present, with the increasing diversification of application scenarios for consumer secondary batteries, especially the development of virtual reality technology, the demand for curved secondary batteries that match head-mounted electronic products is becoming increasingly strong. Currently, well-known domestic and international giants have entered this field and have successfully launched a number of head-mounted virtual reality electronic products.

[0032] Since the electrode assembly in this head-mounted electronic product needs to match the terminal battery compartment, it is usually designed to be an arc-shaped electrode assembly. However, this arc-shaped electrode assembly will experience arc rebound during manufacturing and use, which can easily lead to black spots on the outermost layer of the electrode assembly. The range of the black spots gradually decreases from the outer arc to the inner arc, thereby affecting the safety and reliability of the battery.

[0033] During manufacturing and use, arc-shaped electrode assemblies are typically required to maintain a stable curvature to ensure smooth contact between the cathode and anode electrodes and avoid interface problems caused by increased spacing between the electrodes. Arc-shaped electrode assemblies are bent during manufacturing, which causes the active material layers on the outer arcs of the cathode and anode electrodes to be stretched and the active material layers on the inner arcs to be squeezed. After the pressure is released, the cathode and anode electrodes will rebound in curvature. This phenomenon not only increases the spacing between the electrodes, leading to black spots, but also creates serious appearance issues, impacting the safety and reliability of the battery.

[0034] In order to reduce the curvature rebound phenomenon of the electrode assembly, currently methods such as pressurized shaping and increasing the diaphragm adhesive content and thickness can be used, but these methods will reduce production efficiency, increase production costs, and reduce energy density.

[0035] In order to effectively reduce the curvature rebound problem of the electrode assembly, an anode electrode can be designed. By performing a differentiated rebound design, the curvature rebound phenomenon of the electrode assembly can be reduced, the black spot problem can be reduced, and the safety and reliability of the battery can be improved.

[0036] An embodiment of the present application provides an electronic device, which can be any electronic device, such as a VR device, a mobile phone, a laptop computer, a video camera, a digital camera, an electric toy, an electric car, etc. The electronic device is provided with an electrochemical device for providing electrical energy.

[0037] According to some embodiments of the present application, the present application provides an anode plate 1110. Figure 1 is a structural schematic diagram of the anode plate 1110 provided in an embodiment of the present application. The anode plate 1110 is bent toward a first direction X. The anode plate 1110 includes an outer arc anode material layer, an anode current collector 1113 and an inner arc anode material layer arranged in sequence along the first direction X. The outer arc anode material layer includes a first anode material layer and a second anode material layer. The second anode material layer 1112 is arranged between the first anode material layer 1111 and the anode current collector 1113; the first anode material layer includes graphite, and the second anode material layer and the inner arc anode material layer both include hard carbon.

[0038] The anode plate 1110 is bent in the first direction X, which means that the anode plate 1110 is arched toward one side. The present application does not limit the degree of curvature of the anode plate 1110, which can be the same or different. For arc-shaped cells, electrode assemblies with the same degree of curvature at all locations are more common, so this article uses electrode assemblies with the same degree of curvature at all locations as an example. Those skilled in the art will understand that the description of the anode plate 1110 with the same degree of curvature at all locations in the present application is only a specific description of what can be achieved in this solution, and is not intended to limit the present invention. In other embodiments, the degree of curvature of the curved anode plate 1110 at various locations may be different.

[0039] In the anode electrode 1110, the anode current collector 1113 has two surfaces opposite to each other in the direction of its own thickness. The first anode material layer 1111 and the second anode material layer 1112 are located on the outer arc surface of the anode current collector 1113, and the inner arc anode material layer 1114 is located on the inner arc surface of the anode current collector 1113. The "outer arc" and "inner arc" are based on the positions in the bent state. The "outer arc" refers to the arched surface or position of the bent anode current collector 1113, and the "inner arc" refers to the concave surface or position of the bent anode current collector 1113.

[0040] The graphite in the embodiments of the present application may be natural graphite, artificial graphite, or modified graphite; the hard carbon may be resin carbon, organic polymer pyrolytic carbon, or carbon black.

[0041] In some embodiments, the anode current collector 1113 can be any material suitable for use as an anode current collector 1113 in lithium-ion batteries, specifically a metal foil or a composite current collector. Alternatively, the anode current collector 1113 includes copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

[0042] The anode electrode 1110 of the embodiment of the present application adopts a rebound difference design. The first anode material layer 1111 in the outer arc anode material layer contains graphite and can be designed as an anode material layer with large rebound. The second anode material layer 1112 contains hard carbon and can be designed as an anode material layer with small rebound. The inner arc anode material layer 1114 located in the inner arc contains hard carbon and can be designed as an anode material layer with small rebound. The first anode material layer 1111 may not contain hard carbon or only add a small amount of hard carbon, the second anode material layer 1112 and the inner arc anode material layer 1114 may respectively not contain graphite or only add a small amount of graphite. In order to achieve the rebound difference, the graphite mass content of the first anode material layer 1111 is greater than the graphite mass content of the second anode material layer 1112, and the hard carbon mass content of the first anode material layer 1111 is less than the hard carbon mass content of the second anode material layer 1112, the graphite mass of the first anode material layer 1111 is greater than the graphite mass content of the inner arc anode material layer 1114, and the hard carbon mass content of the first anode material layer 1111 is less than the hard carbon mass content of the inner arc anode material layer 1114. This rebound difference design allows the arc-shaped battery cell to generate shear stress on the second anode material layer 1112 and the inner arc anode material layer 1114 with smaller rebound along the plane direction of the anode electrode 1110 during use, thereby reducing the arc rebound phenomenon. At the same time, along the thickness direction of the anode electrode 1110, the first anode material layer 1111 with larger rebound can also supplement the outer arc space to reduce the slippage and spacing between the electrodes, thereby improving the safety and reliability of the battery.

[0043] According to some embodiments of the present application, the median particle size Dv50 of graphite is 10 to 20 μm, and the median particle size Dv50 of hard carbon is 2 to 10 μm. For example, the median particle size Dv50 of graphite can be 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm, or any intermediate value between the above two values; the median particle size Dv50 of hard carbon can be 2 μm, 4 μm, 6 μm, 8 μm, or 10 μm, or any intermediate value between the above two values.

[0044] In some embodiments of the present application, the median particle size Dv50 of graphite is larger than the median particle size Dv50 of hard carbon. By detecting the median particle size of the anode material in the anode material layer, it can be determined whether it is graphite or hard carbon.

[0045] According to some embodiments of the present application, the compacted density of graphite powder is 1.5 to 2.0 g / cm 3 The compacted density of hard carbon powder is 0.5~1.5g / cm 3 For example, the graphite powder compaction density is 1.5 g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 or 2.0g / cm 3 , or any intermediate value between the above two values; the compacted density of hard carbon powder is 0.5g / cm 3 , 0.7g / cm 3 , 1g / cm 3 , 1.2g / cm 3 or 1.5g / cm 3 , or it can be an intermediate value between any of the above two values.

[0046] In some embodiments of the present application, the powder compaction density of graphite is greater than the powder compaction density of hard carbon. By detecting the powder compaction density of the anode material in the anode material layer, it can be determined whether it is graphite or hard carbon.

[0047] The median particle size Dv50 in the embodiments of the present application is measured using a laser particle size analyzer. The powder compaction density is measured in accordance with GB / T 24533-2009 "Graphite-based negative electrode materials for lithium-ion batteries," and is calculated using density = mass / volume.

[0048] According to some embodiments of the present application, the anode plate 1110 satisfies at least one of the following conditions:

[0049] (1) The first anode material layer 1111 includes a binder and a dispersant. Based on the mass of the first anode material layer, the mass percentage of graphite is 96-98%, the mass percentage of the binder is 1-2%, and the mass percentage of the dispersant is 1-2%; (2) The second anode material layer 1112 includes a binder and a dispersant. Based on the mass of the second anode material layer 1112, the mass percentage of hard carbon is 96-98%, the mass percentage of the binder is 1-2%, and the mass percentage of the dispersant is 1-2%; (3) The inner arc anode material layer 1114 includes a binder and a dispersant. Based on the mass of the inner arc anode material layer 1114, the mass percentage of hard carbon is 96-98%, the mass percentage of the binder is 1-2%, and the mass percentage of the dispersant is 1-2%.

[0050] According to some embodiments of the present application, the first anode material layer 1111, the second anode material layer 1112 and the inner arc anode material layer 1114 all include a binder, and the binders of the first anode material layer 1111, the second anode material layer 1112 and the inner arc anode material layer 1114 are independently selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, alginic acid and sodium alginate.

[0051] According to some embodiments of the present application, the first anode material layer 1111, the second anode material layer 1112 and the inner arc anode material layer 1114 all include a dispersant, and the dispersants of the first anode material layer 1111, the second anode material layer 1112 and the inner arc anode material layer 1114 are independently selected from at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0052] According to some embodiments of the present application, the relationship between the thickness a1 of the first anode material layer 1111 and the thickness A of the outer arc anode material layer satisfies a1: A=0.25-0.75.

[0053] According to some embodiments of the present application, the relationship between the thickness a1 of the first anode material layer 1111 and the thickness A of the outer arc anode material layer satisfies a1: A=0.4-0.6.

[0054] For example, the ratio of a1:A may be 0.25, 0.3, 0.4, 0.5, 0.6 or 0.75, etc. It may also be any value within the range of 0.25 to 0.75.

[0055] According to some embodiments of the present application, the relationship between the thickness A of the outer arc anode material layer and the thickness B of the inner arc anode material layer 1114 satisfies B≤A≤2B.

[0056] According to some embodiments of the present application, the relationship between the thickness A of the outer arc anode material layer and the thickness B of the inner arc anode material layer 1114 satisfies 1.3B≤A≤1.7B.

[0057] For example, the value of A / B may be 1, 1.3, 1.5, 1.7 or 2, etc. It may also be any value within the range of 1 to 2.

[0058] According to some embodiments of the present application, the present application provides an electrochemical device, which includes the anode plate 1110 of any of the above solutions.

[0059] According to some embodiments of the present application, the electrochemical device further includes a cathode electrode sheet and an isolation membrane. The anode electrode sheet 1110, the cathode electrode sheet, and the isolation membrane constitute an electrode assembly. Each layer of anode electrode sheet 1110 corresponds to a layer of cathode electrode sheet, and an isolation membrane is provided to separate the anode electrode sheet 1110 and the cathode electrode sheet to form an electrode sheet unit. Exemplarily, each electrode sheet unit includes: 1 layer of anode electrode sheet 1110, 1 layer of cathode electrode sheet, and 2 layers of isolation membrane.

[0060] In some embodiments, the electrode assembly is bent toward the first direction X, that is, each electrode unit is bent toward the first direction X.

[0061] According to some embodiments of the present application, the cathode electrode sheet includes a cathode current collector and a cathode active material layer, and the cathode active material layer includes a cathode active material, a binder and a conductive agent.

[0062] In some embodiments, the cathode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.

[0063] In some embodiments, the cathode active material includes at least one of lithium cobaltate, lithium nickel manganese cobaltate, lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel lithium manganese oxide, spinel lithium nickel manganese oxide, and lithium titanate.

[0064] In some embodiments, the binder comprises an adhesive polymer, such as at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane. In some embodiments, the polyolefin binder comprises at least one of polyethylene, polypropylene, polyolefin ester, polyolefin alcohol, or polyacrylic acid.

[0065] In some embodiments, the conductive agent includes a carbon-based material, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black or carbon fiber; a metal-based material, such as metal powder or metal fiber of copper, nickel, aluminum, silver, etc.; a conductive polymer, such as a polyphenylene derivative; or a mixture thereof.

[0066] The present application has no particular limitation on the material and shape of the isolation membrane, which may be any material disclosed in the prior art.

[0067] In some embodiments, the isolation film includes a polymer or inorganic material formed of a material that is stable to the electrolyte of the present application. For example, the isolation film may include a substrate layer and a surface treatment layer.

[0068] The substrate layer is a non-woven fabric, film, or composite film having a porous structure. The material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric, or polypropylene-polyethylene-polypropylene porous composite film can be used.

[0069] A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic material. The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer includes a polymer, and the polymer material is selected from at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0070] In some embodiments, the electrochemical device further includes a housing, wherein the electrode assembly is housed in the housing.

[0071] In some embodiments, the electrochemical device further includes an electrolyte within the housing, the electrolyte comprising an organic solution, specifically comprising a combination of one or more of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, methyl acetate, ethylene carbonate (EC), propylene carbonate (PC), and propylene carbonate.

[0072] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of an organic lithium salt and an inorganic lithium salt. Optionally, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalatoborate) LiB(C2O4)2 (LiBOB), and lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB).

[0073] The housing can be used to encapsulate the electrode assembly and electrolyte. According to some embodiments of the present application, the housing is a packaging bag, illustratively a soft-pack packaging bag. The soft-pack packaging bag can be made of plastic, specifically polypropylene, polybutylene terephthalate, polybutylene succinate, etc.

[0074] According to some embodiments of the present application, the present application provides an electronic device, which includes the electrochemical device of any of the above schemes, and the electrochemical device is used to provide electrical energy for the electronic device.

[0075] According to some embodiments of the present application, the present application provides a method for preparing an electrochemical device according to any of the above schemes, which comprises the following steps:

[0076] A first anode material layer and a second anode material layer are coated on one side of the anode current collector 1113 by die extrusion double-layer coating, and an inner arc anode material layer is coated on the other side to obtain an anode pole piece 1110;

[0077] The anode plates 1110 are stacked in sequence and bent through a bending process.

[0078] As an implementation method, the processing process of the electrochemical device is: stirring - coating - cold pressing - striping - lamination - bending - transfer welding - packaging - vacuum baking - liquid injection - standing - formation - vacuuming - capacity - visual inspection. The bending process is to place the straight lamination assembly in an arc-shaped fixture, stand it at 50-90°C and 1-3MPa pressure, and bend it in the middle to form an arc-shaped electrode assembly.

[0079] Next, one or more embodiments will be described in more detail with reference to the following examples. Of course, these examples do not limit the scope of one or more embodiments.

[0080] Example

[0081] A secondary battery, the assembly process is as follows:

[0082] Preparation of anode electrode:

[0083] The anode material graphite (having a certain median particle size Dv50 and powder compaction density), the dispersant sodium carboxymethyl cellulose CMC, and the binder styrene-butadiene rubber are mixed in a mass ratio of 97:1:2, and deionized water is added to obtain a first anode slurry with a solid content of 50% under the action of a vacuum mixer;

[0084] The anode material hard carbon (which has a certain median particle size Dv50 and powder compaction density), the dispersant sodium carboxymethyl cellulose CMC, and the binder styrene-butadiene rubber are mixed in a mass ratio of 97:1:2, deionized water is added, and a second anode slurry with a solid content of 50% is obtained under the action of a vacuum mixer.

[0085] The anode material hard carbon (which has a certain median particle size Dv50 and a powder compaction density of 1.2 g / cm 3 ), dispersant sodium carboxymethyl cellulose CMC, and binder styrene-butadiene rubber are mixed in a mass ratio of 97:1:2, deionized water is added, and a third anode slurry is obtained under the action of a vacuum mixer with a solid content of 50%.

[0086] A die head extrusion double-layer coating method is used to coat a first anode slurry for forming a first anode material layer and a second anode slurry for forming a second anode material layer on one side of an anode collector copper foil with a thickness of 10 μm. The second anode slurry is adjacent to the anode collector. A third anode slurry for forming an inner arc anode material layer is coated on the other side of the anode collector. The mixture is dried at 110°C, cold pressed, and cut to obtain an anode pole piece. The thickness of the first anode material layer is a1, the thickness of the second anode material layer is a2, the thickness of the outer arc anode material layer is A = thickness a1 + thickness a2, and the thickness of the inner arc anode material layer is B.

[0087] Preparation of cathode electrode:

[0088] 96 wt% lithium cobalt oxide, 2 wt% superconducting carbon black, and 2 wt% binder polyvinylidene fluoride were mixed, and N-methylpyrrolidone was used as solvent. The cathode active slurry was mixed thoroughly with 0.3 g / 1540.25 mm 2 The coating amount is coated on both surfaces of a cathode current collector aluminum foil with a thickness of 9 μm and then dried to obtain a cathode active slurry layer; then cold pressing, cutting and bending are performed to obtain a cathode electrode sheet.

[0089] Preparation of electrode assembly:

[0090] The separator is made of PP (polypropylene) and has a thickness of 20μm. The anode electrode, separator, cathode electrode, and separator are repeatedly stacked in sequence to form a 24-layer stack. This stack is then bent to form an electrode assembly.

[0091] Preparation of secondary batteries:

[0092] The electrode assembly is placed in a packaging bag, and an electrolyte is injected, followed by formation to obtain an electrochemical device. The solute in the electrolyte is 2 mol / L lithium hexafluorophosphate, and the solvent in the electrolyte is ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1.

[0093] Comparative Example

[0094] A secondary battery, the assembly process of which is substantially the same as that of Example 1, the main difference being that the anode materials used in the inner arc anode material layer and / or the outer arc anode material layer are different.

[0095] The main parameters of each embodiment and comparative example are shown in Table 1 below:

[0096] Table 1 Parameters of each embodiment and comparative example

[0097] The secondary batteries provided in each embodiment and comparative example were subjected to a radian change rate test and a cycle capacity retention rate test. The test process is as follows:

[0098] Electrode assembly arc change rate test: ① Obtaining the initial arc radius: Before the secondary battery is cycled, use a 3D profilometer to scan the 3D structure of the electrode assembly surface, then average the scanned surface to obtain an arc line, fit three points on the arc line to obtain a standard arc line, and then read the arc radius a. ② Obtaining the arc radius after 800 cycles: After the secondary battery completes the cycle test, use a 3D profilometer to scan the 3D structure of the electrode assembly surface, then average the scanned surface to obtain an arc line, fit three points on the arc line to obtain a standard arc line, and then read the arc radius b. ③ Obtaining the arc radius change rate: The arc radius change rate of the electrode assembly 1000 is (b a) / a.

[0099] Secondary battery cycle capacity retention rate test: The secondary battery is charged at a constant current of 0.5C to the full charge voltage of the system, the constant voltage is increased to 0.05C, and the full discharge is performed to 3.0V under the condition of a constant current of 0.5C. This is one cycle, and a total of 800 cycles are performed. The cycle capacity retention rate test = discharge capacity in the Nth cycle mAh / initial discharge capacity in the first cycle mAh.

[0100] The test results are shown in Table 2:

[0101] Table 2 Test results

[0102] Combined with the results in Table 2, we can see that:

[0103] Compared with comparative examples 1 to 3, the outer arc anode material layer of the anode pole pieces of embodiments 1 to 18 includes a first anode material layer and a second anode material layer, the second anode material layer is adjacent to the anode current collector, and the first anode material layer includes graphite, and the second anode material layer and the inner arc anode material layer both include hard carbon, which can reduce the curvature rebound phenomenon of the battery cell and improve the cycle performance of the battery cell.

[0104] According to Examples 1 to 3, when the median particle size Dv50 of the graphite contained in the anode plate is 10 to 20 μm and the compacted density of the graphite powder is 1.5 to 2.0 g / cm 3 , which can reduce the curvature rebound phenomenon of the battery cell and improve the cycle performance of the battery cell.

[0105] According to Example 1, and Examples 4 to 6, when the median particle size Dv50 of the hard carbon contained in the anode plate is 2 to 10 μm, the compacted density of the hard carbon powder is 0.5 to 1.5 g / cm 3 , which can reduce the curvature rebound phenomenon of the battery cell and improve the cycle performance of the battery cell.

[0106] According to Example 1, and Examples 7 to 12, the relationship between the thickness a1 of the first anode material layer and the thickness A of the outer arc anode material layer satisfies a1: A = 0.25 to 0.75, preferably 0.4 to 0.6, which can reduce the curvature rebound phenomenon of the battery cell and improve the cycle performance of the battery cell.

[0107] According to Example 1, and Examples 13 to 18, the relationship between the thickness A of the outer arc anode material layer and the thickness B of the inner arc anode material layer satisfies A / B=1 to 2, preferably 1.3 to 1.7, which can reduce the curvature rebound phenomenon of the battery cell and improve the cycle performance of the battery cell.

[0108] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. An anode electrode, characterized in that: The anode electrode sheet is bent in a first direction X, and includes an outer arc anode material layer, an anode current collector, and an inner arc anode material layer sequentially arranged along the first direction X. The outer arc anode material layer includes a first anode material layer and a second anode material layer, and the second anode material layer is arranged between the first anode material layer and the anode current collector; The first anode material layer includes graphite, and the second anode material layer and the inner arc anode material layer both include hard carbon.

2. The anode plate according to claim 1, characterized in that: The median particle size Dv50 of the graphite is 10 to 20 μm, and the median particle size Dv50 of the hard carbon is 2 to 10 μm.

3. The anode plate according to claim 1, characterized in that: The graphite powder compaction density is 1.5 to 2.0 g / cm 3 The compacted density of the hard carbon powder is 0.5 to 1.5 g / cm 3 .

4. The anode plate according to any one of claims 1 to 3, characterized in that: The anode plate satisfies at least one of the following conditions: (1) The first anode material layer includes a binder, and based on the mass of the first anode material layer, the mass percentage of the graphite is 96-98%, and the mass percentage of the binder is 1-2%; (2) the second anode material layer includes a binder, and based on the mass of the second anode material layer, the mass percentage of the hard carbon is 96-98%, and the mass percentage of the binder is 1-2%; (3) The inner arc anode material layer includes a binder. Based on the mass of the inner arc anode material layer, the mass percentage of the hard carbon is 96-98%, and the mass percentage of the binder is 1-2%.

5. The anode plate according to claim 4, characterized in that: The first anode material layer, the second anode material layer and the inner arc anode material layer all include a binder, and the binders of the first anode material layer, the second anode material layer and the inner arc anode material layer are independently selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, alginic acid and sodium alginate.

6. The anode plate according to any one of claims 1 to 3, characterized in that: The relationship between the thickness a1 of the first anode material layer and the thickness A of the outer arc anode material layer satisfies a1: A=0.25-0.

75.

7. The anode plate according to claim 6, characterized in that: The relationship between the thickness a1 of the first anode material layer and the thickness A of the outer arc anode material layer satisfies a1: A=0.4-0.

6.

8. The anode plate according to any one of claims 1 to 3, characterized in that: The relationship between the thickness A of the outer arc anode material layer and the thickness B of the inner arc anode material layer satisfies B≤A≤2B.

9. The anode plate according to claim 8, characterized in that: The relationship between the thickness A of the outer arc anode material layer and the thickness B of the inner arc anode material layer satisfies 1.3B≤A≤1.7B.

10. An electrochemical device, characterized in that The electrochemical device comprises the anode piece according to any one of claims 1 to 9.

11. An electronic device, characterized in that: The electronic device comprises the electrochemical device according to claim 10.

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