Pole piece, electrochemical device, and electronic device

Abstract

The application provides a pole piece, an electrochemical device and an electronic device. The pole piece comprises a current collector and an active material layer on the current collector. The active material layer comprises a particle group, the particle group comprises active material particles and first binder particles, the first binder particles bind at least three active material particles, wherein a single particle group comprises the first binder particles and the at least three active material particles bound by the first binder particles, and the particle diameter of the first binder particles in the plurality of particle groups is 0.1-3.5 μm. The composition of the first binder particles of the application comprises polyolefin, which improves the adhesion of the active material particles to the current collector. In addition, the hardness of the polyolefin is small, and the use of the polyolefin in the active material layer also avoids or alleviates the adverse effect on the compaction density of the active material layer.

Description

[0001] This application is a divisional application of the invention patent filed on December 31, 2020, with application number 202080025234.5 (international application number: PCT / CN2020 / 142269), entitled "Electrode, Electrochemical Device and Electronic Device". Technical Field

[0002] This application relates to the field of electrochemical energy storage, and in particular to electrodes, electrochemical devices and electronic devices. Background Technology

[0003] With the development and advancement of electrochemical devices (e.g., lithium-ion batteries), increasingly higher demands are being placed on their energy density and safety performance. Although current technologies for improving electrochemical devices can enhance their energy density and safety performance to some extent, they are still unsatisfactory and require further improvement. Summary of the Invention

[0004] An embodiment of this application provides an electrode, which includes a current collector and an active material layer located on the current collector. The active material layer includes multiple particle groups, each particle group comprising a first binder particle and at least three active material particles bonded together by the first binder particle, wherein the particle size of the first binder particle in the multiple particle groups is 0.1-3.5 μm.

[0005] In some embodiments, the particle size of the first binder particle in the plurality of particle groups is 0.3-1.5 μm.

[0006] In some embodiments, the first binder particles comprise polyolefins.

[0007] In some embodiments, the polyolefin includes at least one of polypropylene or polyethylene.

[0008] In some embodiments, the particle size of the active material particles in the plurality of particle groups is from 1 μm to 40 μm.

[0009] In some embodiments, the at least three active material particles include a first active material particle, a second active material particle, and a third active material particle. The particle size of the first active material particle in the plurality of particle groups is 4 μm to 17 μm larger than the particle size of the second active material particle in the plurality of particle groups. The ratio of the particle size of the first active material particle in the plurality of particle groups to the particle size of the second active material particle in the plurality of particle groups is 2:1 to 7:1. The particle size of the second active material particle in the plurality of particle groups is 0.01 μm to 8 μm larger than the particle size of the third active material particle in the plurality of particle groups. Furthermore, the ratio of the particle size of the second active material particle in the plurality of particle groups to the particle size of the third active material particle in the plurality of particle groups is greater than 1 and less than or equal to 4.

[0010] In some embodiments, the active material layer further includes a second adhesive, the second adhesive comprising at least one of polyacrylate, polyacrylic acid, polyacrylate, polymethyl methacrylate, polyacrylonitrile, polyamide, or sodium carboxymethyl cellulose.

[0011] In some embodiments, the percentage of the total mass of the first binder particles and the second binder is 0.5% to 8% based on the total mass of the active material layer, and the mass ratio of the first binder particles to the second binder is 1:10 to 10:1.

[0012] In some embodiments, the electrode is a positive electrode, and the active material layer includes at least one of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxide phosphate, sodium vanadium oxide phosphate, lithium vanadium oxide phosphate, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, or lithium nickel cobalt aluminum oxide.

[0013] Another embodiment of the present invention provides an electrochemical device, which includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is an electrode provided in the embodiment of the present invention.

[0014] Another embodiment of the present invention provides an electronic device, including the electrochemical device provided in the embodiments of the present invention.

[0015] The first binder particles of this application comprise polyolefins, which improves the adhesion between the active material particles and the current collector. Furthermore, the low hardness of polyolefins and their use in the active material layer also avoids or mitigates the adverse effects on the compaction density of the active material layer. On the other hand, this application provides a preferred size relationship between the binder particles and the active material particles bonded to them in the active material layer. This size relationship results in a more compact spatial arrangement of the binder particles and active material particles, improving the volume utilization of the active material layer. Furthermore, this can increase the energy density of the electrochemical device including this active material layer. Attached Figure Description

[0016] Figure 1A A schematic diagram of an electrochemical device 100 in some embodiments of this application is shown.

[0017] Figure 1B A schematic diagram of the electrode assembly 1 of the electrochemical device 100 in some embodiments of this application is shown.

[0018] Figure 2 Schematic diagrams of electrodes in some embodiments of this application are shown.

[0019] Figure 3 It shows Figure 2 A cross-sectional view of the intermediate electrode along its thickness direction.

[0020] Figure 4 and Figure 5 Scanning electron microscope (SEM) images of the active material layer of the positive electrode 10 in Examples 1 and 4 are shown respectively.

[0021] Figure 6 Scanning electron microscope (SEM) images of the active material layer of the positive electrode 10 in some embodiments of this application are shown. Detailed Implementation

[0022] The following embodiments are intended to enable those skilled in the art to fully understand this application, but do not limit this application in any way.

[0023] Figure 1A This is a schematic diagram of an electrochemical device 100 in some embodiments of this application. The electrochemical device 100 includes an electrode assembly 1. The electrode assembly 1 may include a positive electrode 10, a negative electrode 12, and a separator 11 disposed between the positive electrode 10 and the negative electrode 12.

[0024] In some embodiments, the electrochemical device 100 may be formed by winding or stacking electrode assemblies 1. For example, in some embodiments of this application, the positive electrode 10, the separator 11, and the negative electrode 12 are sequentially wound or stacked to form the electrode assembly 1, then encapsulated in, for example, an aluminum-plastic film, injected with electrolyte, formed, and encapsulated to form the electrochemical device 100. The positive electrode 10, the separator 11, and the negative electrode 12 are immersed in the electrolyte. A description of the electrode assembly 1, the positive electrode 10, and the negative electrode 12 can be found in this application. Figure 1B And its related descriptions.

[0025] In some embodiments, the electrochemical device 100 may be a lithium-ion battery, but this application is not limited thereto. In some embodiments, the electrochemical device 100 may further include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte solution, wherein the electrolyte solution includes a lithium salt and a non-aqueous solvent. The lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, or lithium difluoroborate. For example, LiPF6 is selected as the lithium salt because it has high ionic conductivity and can improve cycle characteristics.

[0026] The non-aqueous solvent may be a carbonate compound, a carboxylic acid ester compound, an ether compound, other organic solvents, or a combination thereof.

[0027] Carbonate compounds can be chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.

[0028] Examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), or combinations thereof. Examples of fluorinated carbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or combinations thereof.

[0029] Examples of carboxylic acid ester compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonic acid lactone, caprolactone, methyl formate, or combinations thereof.

[0030] Examples of ether compounds are dibutyl ether, tetraethylene dimethyl ether, diethylene dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or combinations thereof.

[0031] Examples of other organic solvents include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.

[0032] Those skilled in the art will understand that the electrochemical device 100 (e.g., a lithium-ion battery) and the method for preparing the electrochemical device 100 described above are merely illustrative and should not be used to limit the scope of this application. Other electrochemical devices 100 may be used, and other methods commonly used in the art may be employed to prepare the electrochemical device 100 without departing from the disclosure of this application. For example, although... Figure 1A The electrochemical device in the present application is bag-shaped. However, the electrochemical device according to the embodiments of this application may be other shapes, such as rectangular, cylindrical, coin-shaped, etc.

[0033] Figure 1B A schematic diagram of the electrode assembly 1 of the electrochemical device 100 in some embodiments of this application is shown. Figure 1B As shown, the electrode assembly 1 includes a positive electrode 10, a negative electrode 12, and a separator 11 disposed between the positive electrode 10 and the negative electrode 12. The positive electrode 10 consists of a positive current collector and a positive active material layer coated on at least one surface of the positive current collector. The negative electrode 11 consists of a negative current collector and a negative active material layer coated on at least one surface of the negative current collector. Descriptions of the positive current collector, the positive active material layer, the negative current collector, and the negative active material layer can be found in [reference needed]. Figure 2 And its corresponding description.

[0034] In some embodiments, the separator 11 comprises at least one selected from polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene comprises at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Polyethylene and polypropylene, in particular, are effective in preventing short circuits and can improve battery stability through a turn-off effect. In some embodiments, the thickness of the separator 11 is in the range of about 5 μm to 500 μm.

[0035] In some embodiments, the surface of the separator 11 may further include a porous layer disposed on at least one surface of the substrate of the separator 11. The porous layer comprises inorganic particles and a binder. The inorganic particles are selected from at least one of alumina (Al2O3), silicon oxide (SiO2), magnesium oxide (MgO), titanium oxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium dioxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. In some embodiments, the pores of the separator 11 have a diameter in the range of about 0.01 μm to 1 μm. The binder for the porous layer is selected from at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The porous layer on the surface of the separator 11 can improve the heat resistance, oxidation resistance, and electrolyte wetting properties of the separator 11, and enhance the adhesion between the separator 11 and the electrode.

[0036] Figure 2 A schematic diagram of an electrode sheet in some embodiments of this application is shown. The electrode sheet includes a current collector 20 and an active material layer 21 disposed on the current collector 20. In some embodiments, the electrode sheet may be the positive electrode sheet 10 and / or the negative electrode sheet 12 shown in FIG. 1.

[0037] When the electrode is the positive electrode 10, the current collector 20 is the positive current collector. The active material layer 21 is the positive active material layer.

[0038] The positive current collector is a structure or component that collects positive current. In some embodiments, the positive current collector is an Al foil. Of course, other positive current collectors commonly used in the art can also be used. In some embodiments, the thickness of the positive current collector can be from 1 μm to 200 μm.

[0039] A portion of the positive electrode current collector is coated with a layer of positive electrode active material. In some embodiments, the thickness of the active material layer can be from 10 μm to 500 μm.

[0040] The positive electrode active material layer includes the positive electrode active substance, the positive electrode conductive agent, and the positive electrode binder.

[0041] The positive electrode active material may be a material that allows reversible insertion and extraction of lithium ions. In some embodiments, the positive electrode active material uses a compound that allows reversible insertion and extraction of lithium ions. For example, the positive electrode active material may include at least one of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxide phosphate, sodium vanadium oxide phosphate, lithium vanadium oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, or lithium nickel cobalt aluminum oxide.

[0042] The positive electrode conductive agent provides conductivity to the positive electrode. For example, the positive electrode conductive agent can achieve electrical contact between the positive electrode active material and the positive electrode current collector, thereby providing conductivity to the positive electrode. The positive electrode conductive agent may include at least one of conductive carbon black, Ketjen black, sheet graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the mass ratio of the active material, conductive agent, and binder in the active material layer may be (70 to 98):(1 to 15):(1 to 15). It should be understood that the above description is merely an example, and the active material layer of the positive electrode 10 may use any other suitable material, thickness, and mass ratio.

[0043] The positive electrode binder bonds the positive electrode conductive agent and the positive electrode active material to the positive electrode current collector. Positive electrode binders may include resin-based polymers such as polyethylene, polypropylene, sodium polyacrylate, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or their hydrogenated products; and EPDM (ethylene-propylene-diene terpolymer). Thermoplastic elastomers such as styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers, or their hydrogenated products; soft resinous polymers such as polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene-ethylene copolymers, and polytetrafluoroethylene-vinylidene fluoride copolymers; or other polymer compositions with ion conductivity of alkali metal ions (especially lithium ions). Preferably, the positive electrode binder is a polyolefin, such as at least one of polyethylene and polypropylene.

[0044] When the electrode is the negative electrode 12, the current collector 20 is the negative electrode current collector. The active material layer 21 is the negative electrode active material layer.

[0045] The negative electrode current collector is a structure or component that collects negative electrode current. In some embodiments, the current collector of the negative electrode 12 may be at least one of copper foil, nickel foil, or carbon-based current collector.

[0046] The negative electrode active material layer includes the negative electrode active substance, the negative electrode conductive agent, and the negative electrode binder.

[0047] The negative electrode active material may include materials that allow reversible insertion and extraction of lithium ions. For example, it may include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, tin, silicon-carbon, silicon-oxygen, or lithium titanate.

[0048] The negative electrode conductive agent provides conductivity to the negative electrode. For example, the negative electrode conductive agent can achieve electrical contact between the negative electrode active material and the negative electrode current collector, thereby providing conductivity to the negative electrode. The negative electrode conductive agent may include at least one of conductive carbon black, Ketjen black, sheet graphite, graphene, carbon nanotubes, carbon fibers, copper (Cu), nickel (Ni), aluminum (Al), silver (Ag) metal powders or fibers, or conductive polymers such as polyphenylene derivatives. In some embodiments, the mass ratio of the negative electrode active material (e.g., silicon-based materials and carbon materials), conductive agent, and binder (including a first binder and a second binder) in the active material layer may be (70 to 98): (1 to 15): (1 to 15). It should be understood that the above description is merely an example, and any other suitable materials and mass ratios may be used.

[0049] The negative electrode binder bonds the negative electrode conductive agent and the negative electrode active material to the negative electrode current collector. The negative electrode binder may include at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber (SBR), acrylated (acrylic-modified) SBR, epoxy resin, or nylon.

[0050] It should be understood that, although Figure 2 The active material layer 21 is shown as being disposed on both sides of the current collector 20, but this is merely exemplary and not intended to limit the scope of this application. The active material layer 21 may be disposed on one or both sides of the current collector 20. In some embodiments, the active material layer 21 may be disposed on only one side of the current collector 20. Although Figure 2 The current collector 20 and the active material layer 21 are shown in direct contact, but in some embodiments, an additional layer may be disposed between the current collector 20 and the active material layer 21. In some embodiments, the current collector 20 may be disposed only on a portion of the surface of the active material layer 21.

[0051] According to some embodiments of this application, Figure 3 To show Figure 2 A cross-sectional view of the intermediate electrode along its thickness direction.

[0052] like Figure 3As shown, in some embodiments, the active material layer 21 includes a particle group 30, which comprises active material particles 301 and first binder particles 302. In the active material layer 21, the first binder particles 302 serve to bind the active material particles 301. The active material particles 301 bonded to the first binder particles 302 constitute the particle group 30. It should be understood that only one particle group 30 is shown in the figure. In some embodiments, the active material layer 21 includes multiple particle groups 30.

[0053] The active material particles 301 and the first binder particles 302 may have the same or different particle sizes.

[0054] In some embodiments, the particle size of a single particle (e.g., the first binder particle 302, the active material particle 301, etc.) of this application can be determined by: determining the cross-sectional area of ​​the particle; and determining the diameter of a circle with the same cross-sectional area as the particle size. In some embodiments, the particle size of the particles of this application can be determined by: determining the length of the longest diagonal of the particle, determining the length of the shortest diagonal of the particle, and the particle size being the arithmetic mean of the lengths of the longest and shortest diagonals. In some embodiments, the length of the longest diagonal of the particle is the particle size. In some embodiments, the length of the longest side of the particle is the particle size. In some embodiments, a scanning electron microscope can be used to scan the cross-section of the electrode along the thickness direction to determine the cross-sectional area of ​​the particle, the length of the longest diagonal, the length of the shortest diagonal, and / or the longest side of the particle. In some embodiments, the electrode processing and scanning can be performed with reference to the method provided in Embodiment 1 of this application.

[0055] The first binder particle 302 can bind multiple particles. In some embodiments, the first binder particle 302 binds at least three active material particles. Figure 3 As shown, in some embodiments, at least three active material particles 301 include a first active material particle 3011, a second active material particle 3012, and a third active material particle 3013. The first active material particle 3011, the second active material particle 3012, and the third active material particle 3013 may have the same or different particle sizes. In some embodiments, the first active material particle 3011, the second active material particle 3012, and the third active material particle 3013 have different particle sizes. By employing active material particles of various sizes, the packing efficiency between active material particles is increased, packing porosity is reduced, the volume utilization rate of the active material layer is improved, and the energy density of the electrochemical device 100 is enhanced.

[0056] In some embodiments, the particle size of the first active material particle 3011 is larger than that of the second active material particle 3012, and the particle size of the second active material particle 3012 is larger than that of the third active material particle 3013. In some embodiments, the first active material particle 3011, the second active material particle 3012, and the third active material particle 3013 are the top three active material particles in descending order of particle size among the active material particles bonded by the corresponding first binder particles 302.

[0057] The first active material particle 3011 can be bonded by at least one binder particle 302. In some embodiments, the ratio of the length of the edge of the cross-section of the first active material particle 3011 bonded to the first binder particle 302 to the perimeter of the cross-section of the first active material particle 3011 is 0.05 to 0.2. In some embodiments, a first active material particle 3011 may be bonded to multiple first binder particles 302, and the ratio of the length of the cross-section of the first active material particle 3011 in physical contact with the multiple first binder particles 302 to the total perimeter of the first active material particle 3011 is the ratio of the length of the edge of the cross-section of the first active material particle 3011 bonded to the first binder particle 302 to the perimeter of the cross-section of the first active material particle 3011. In some embodiments, this ratio can be determined by scanning the cross-section of the electrode sheet in the thickness direction using a scanning electron microscope. In some embodiments, the electrode sheet can be processed and scanned with reference to the method provided in Embodiment 1 of this application. It should be understood that this is only exemplary, and other suitable methods can also be used. Figure 6 As shown, the edge of the cross-section of the first active material particle 3011 is adjacent to the first binder particle 302 ( Figure 6There are four bonding locations (not shown in the figure), corresponding to the edge lengths of the first active material particles 3011 corresponding to line segments 61, 62, 63, and 64 shown in the figure. In this application, the edge length of the first active material particle 3011 corresponding to a certain line segment (e.g., 61, 62, 63, 64) is the edge length of the first active material particle 3011 defined by the two endpoints of the line segment. The ratio of the sum of the edge lengths of the first active material particles 3011 corresponding to 61, 62, 63, and 64 to the perimeter of the cross-section of the first active material particle 3011 is the ratio of the length of the bond between the edge of the cross-section of the first active material particle 3011 and the first adhesive particle 302 to the perimeter of the cross-section of the first active material particle 3011. In some embodiments, the above ratio may be the result obtained by evaluating the first active material particles 3011 of multiple particle groups 30 under a scanning electron microscope. In some embodiments, if the ratio is too small, the adhesion between the first binder particles 302 and the first active material particles 3011 may be relatively weak, thereby affecting the adhesion between the active material layer 21 and the current collector 20. If the ratio is too large, it indicates that the particle size of the first active material particles 3011 is too small, the specific surface area is too large, the side reactions between the active material particles 301 and the electrolyte increase, and the cycle performance of the electrochemical device 100 is affected.

[0058] Although Figure 3 Only one particle group 30 is shown in the illustration, but this is merely exemplary and not intended to limit the scope of this application. The active material layer 21 may also include one or more other particle groups 30 not shown. In some embodiments, the active material layer 21 includes multiple particle groups 30. For example, a first particle group, a second particle group, a third particle group, ... a Nth particle group. N is a positive integer greater than or equal to 1.

[0059] The first binder particle 302 in the plurality of particle groups 30 has a preferred particle size.

[0060] In some embodiments, the particle size of the first binder particles 302 in the plurality of particle groups 30 is from 0.1 μm to 3.5 μm. Preferably, the particle size of the first binder particles 302 in the plurality of particle groups 30 is from 0.1 μm to 2 μm. Preferably, the particle size of the first binder particles 302 in the plurality of particle groups 30 is from 0.3 μm to 1.5 μm. Preferably, the particle size of the first binder particles 302 in the plurality of particle groups 30 is from 0.5 μm to 1 μm. The particle size of the first binder particles 302 in the plurality of particle groups 30 can be determined based on the particle size of the plurality of first binder particles 302 in the plurality of particle groups 30. In some embodiments, the plurality of first binder particles 302 in the plurality of particle groups 30 have the same particle size. In this case, the particle size of the first binder particles 302 in the plurality of particle groups 30 is equal to the particle size of the first binder particles 302 in a single particle group. In some embodiments, the plurality of first binder particles 302 in the plurality of particle groups 30 have different particle sizes. At this time, the particle size of the first binder particles 302 in the plurality of particle groups 30 is determined as follows: n (e.g., 100) particle groups are randomly selected from the plurality of particle groups 30, namely, the first particle group, the second particle group, ... the nth particle group; the particle size of the first binder particles 302 corresponding to each particle group 30 is determined, resulting in n particle sizes; the range in which more than 50% of the n particle sizes are located is the particle size of the first binder particles 302 in the plurality of particle groups 30. In some embodiments, there may be multiple ranges in which more than 50% of the n particle sizes are located. The narrowest range is selected as the particle size of the first binder particles 302 in the plurality of particle groups 30.

[0061] In some embodiments, when the particle size of the first binder particles 302 in the plurality of particle groups 30 is between 0.1 μm and 3.5 μm, the performance of the electrode can be improved. When the particle size of the first binder particles 302 in the plurality of particle groups 30 is less than 0.1 μm, the number of active material particles bonded around a single first binder particle 302 will be less than 3, and the bonding strength between the active material layer 21 and the current collector 20 will decrease. When the particle size of the first binder particles 302 in the plurality of particle groups 30 is greater than 3.5 μm, the first binder particles 302 are too large and cannot efficiently fill the pores of the active material particles 301, resulting in pores between them. Consequently, the effective bonding area of ​​the first binder particles 302 is reduced, the bonding strength between the active material layer 21 and the current collector 20 is reduced, and the electrode thickness also increases, leading to a decrease in the energy density of the electrochemical device.

[0062] The active material particles 301 in the multiple particle groups 30 have a preferred particle size.

[0063] In some embodiments, the particle size of the active material particles 301 in the plurality of particle groups 30 is from 1 μm to 40 μm. In some embodiments, the particle size of the active material particles 301 in the plurality of particle groups 30 is obtained by evaluating the multiple active material particles 301 under a scanning electron microscope. In some embodiments, the multiple active material particles 301 in the plurality of particle groups 30 have the same particle size. In this case, the particle size of the active material particles 301 in the plurality of particle groups 30 is equal to the particle size of the active material particles 301 in a single particle group. In some embodiments, the multiple active material particles 301 in the plurality of particle groups 30 have different particle sizes. In this case, the particle size of the active material particles 301 in the plurality of particle groups 30 is determined as follows: n (e.g., 100) particle groups are randomly selected from the plurality of particle groups 30, namely, the first particle group, the second particle group, ... the nth particle group; the particle size of the active material particles 301 corresponding to each particle group is determined, resulting in n particle sizes; the range in which more than 50% of the n particle sizes are located is the particle size of the active material particles 301 in the plurality of particle groups 30. In some embodiments, there may be multiple ranges within which more than 50% of the n particle sizes fall. The narrowest range is selected as the particle size of the active material particles 301 in the plurality of particle groups 30. In some embodiments, a single particle group 30 includes a plurality of active material particles 301, and the particle size of the active material particles 301 in a single particle group 30 is the particle size of the largest active material particle in that particle group, i.e., the particle size of the first active material particle 3011.

[0064] In some embodiments, when the particle size of the active material particles 301 in the plurality of particle groups 30 is between 1 μm and 40 μm, the performance of the electrode can be improved. If the particle size of the active material particles 301 in the plurality of particle groups 30 is too small, the specific surface area is too large, the side reactions between the active material particles 301 and the electrolyte increase, and the cycle performance of the electrochemical device is affected. On the other hand, if the particle size of the active material particles 301 in the plurality of particle groups 30 is too large, for example, greater than 40 μm, the packing efficiency between the active material particles 301 decreases, the porosity between the active material particles 301 increases, which reduces the volume utilization rate of the active material layer 21 and reduces the energy density of the electrochemical device. In addition, if the active material particles 301 in the plurality of particle groups 30 are too large, the number of active material particles 301 bonded around a single first binder particle 302 will be reduced, which is not conducive to the bonding between the active material particles 301 and the current collector 20.

[0065] In some embodiments, the particle size of the first active material particle 3011 in the plurality of particle groups 30 is 4 μm to 17 μm larger than the particle size of the second active material particle 3012 in the plurality of particle groups 30, the ratio of the particle size of the first active material particle 3011 to the particle size of the second active material particle 3012 in the plurality of particle groups 30 is 2:1 to 7:1, the particle size of the second active material particle 3012 in the plurality of particle groups 30 is 0.01 μm to 8 μm larger than the particle size of the third active material particle 3013 in the plurality of particle groups 30, and the ratio of the particle size of the second active material particle 3012 to the particle size of the third active material particle 3013 in the plurality of particle groups 30 is greater than 1 and less than or equal to 4.

[0066] In this application, the particle size of the first active material particles 3011 in the plurality of particle groups 30 is obtained by evaluating the first active material particles 3011 in the plurality of particle groups 30 under a scanning electron microscope. In some embodiments, the plurality of first active material particles 3011 in the plurality of particle groups 30 have the same particle size. In this case, the particle size of the first active material particles 3011 in the plurality of particle groups 30 is equal to the particle size of the first active material particles 3011 in a single particle group. In some embodiments, the plurality of first active material particles 3011 in the plurality of particle groups 30 have different particle sizes. In this case, the particle size of the first active material particles 3011 in the plurality of particle groups 30 can be obtained by evaluating the first active material particles 3011 in the plurality of particle groups 30 under a scanning electron microscope. The first active material particles 3011 in the plurality of particle groups 30 in this application can be determined by referring to the method for determining the first binder particles 302 in the plurality of particle groups 30 in this application. Similarly, the particle sizes of the second active material particles 3012 and the third active material particles 3013 in the plurality of particle groups 30 can be determined.

[0067] In this application, the ratio of the particle size of the first active material particle 3011 to the particle size of the second active material particle 3012 in the plurality of particle groups 30 can be determined as follows: n (e.g., 100) particle groups are randomly selected from the plurality of particle groups 30, namely, the first particle group, the second particle group, ... the nth particle group; for each particle group, the ratio of the particle size of the first active material particle 3011 to the particle size of the second active material particle 3012 in that particle group is calculated, resulting in n ratios; the range of these ratios being 50% or higher is the ratio of the particle size of the first active material particle 3011 to the particle size of the second active material particle 3012 in the plurality of particle groups 30. Similarly, the ratio of the particle size of the second active material particle 3012 to the particle size of the third active material particle 3013 in the plurality of particle groups 30 can be determined.

[0068] By setting appropriate ratios and differences in particle sizes among the first active material particles 3011, the second active material particles 3012, and the third active material particles 3013 in multiple particle groups 30, the packing efficiency among the active material particles 301 is improved, the porosity among the active material particles 301 is reduced, and the volume utilization rate of the active material layer is further improved. Applying the aforementioned active material layer to an electrochemical device 100 (e.g., a lithium-ion battery) can increase the energy density of the electrochemical device 100. Furthermore, the number of active material particles 301 bonded around a single first binder particle 302 can be increased, improving the adhesion between the active material particles 301 and the current collector 20.

[0069] In some embodiments, the ratio of the length of the edge of the cross-section of the first active material particle 3011 in the plurality of particle groups 30 bonded to the first binder particle 302 to the perimeter of the cross-section of the first active material particle 3011 is 0.05 to 0.2. In some embodiments, a first active material particle 3011 may be bonded to a plurality of first binder particles 302. The ratio of the length of the cross-section of the first active material particle 3011 in physical contact with the plurality of first binder particles 302 to the total perimeter of the first active material particle 3011 is the ratio of the length of the edge of the cross-section of the first active material particle 3011 bonded to the first binder particle 302 to the perimeter of the cross-section of the first active material particle 3011. In this application, the ratio of the length of the edge of the cross-section of the first active material particle 3011 in the plurality of particle groups 30 bonded to the first binder particle 302 to the perimeter of the cross-section of the first active material particle 3011 can be the result obtained by evaluating the first active material particles 3011 in the plurality of particle groups 30 under a scanning electron microscope. For a single first active material particle 3011, the ratio of the length of the bond between the edge of the cross-section of the first active material particle 3011 and the first binder particle 302 to the perimeter of the cross-section of the first active material particle 3011 can be calculated. Multiple particle groups contain multiple first active material particles 3011. The ratios corresponding to multiple first active material particles 3011 can be determined. The range of ratios exceeding 50% represents the ratio of the length of the bond between the edge of the cross-section of the first active material particle 3011 and the first binder particle 302 to the perimeter of the cross-section of the first active material particle 3011 in the multiple particle groups 30.

[0070] In some embodiments, if the ratio is too small, the adhesion between the first binder particles 302 and the first active material particles 3011 may be relatively weak, thereby affecting the adhesion between the active material layer 21 and the current collector 20. If the ratio is too large, it indicates that the particle size of the first active material particles 3011 is too small, the specific surface area is too large, the side reactions between the active material particles 301 and the electrolyte increase, and the cycle performance of the electrochemical device 100 is affected.

[0071] The active material layer 21 may include at least one binder. In some embodiments, the active material layer 21 includes a first binder, such as first binder particles 302. In some embodiments, the first binder particles 302 are composed of polyolefins. Typically, to improve the adhesion between the active material layer 21 and the current collector 20, the binder content is increased or a high-strength binder is used. However, increasing the binder content has a limited effect on improving the adhesion. For example, when the mass content of the binder polyvinylidene fluoride (PVDF) in the active material layer increases from 1% to 3%, the adhesion strength of the wet active material layer in the electrolyte increases from 9 N / m to 18 N / m, a limited increase. Moreover, reducing the content of the active material leads to a decrease in energy density. In addition, some current high-strength binders have high hardness, and the active material also has high hardness. If the compaction density is increased during the cold pressing stage of the electrode, the electrode is prone to brittle fracture, thus limiting the cold pressing density of the electrode and reducing the energy density. The first binder particles in this application comprise polyolefins, which can bond well with the current collector 20, thereby improving the adhesion between the active material layer 21 and the current collector 20. Furthermore, the polyolefins have low hardness, making them less prone to causing brittle fracture of the electrode sheet during cold pressing, thus reducing the adverse effects of using a hard binder on the compaction density of the electrode sheet. The polyolefins include at least one of polypropylene or polyethylene.

[0072] In some embodiments, the active material layer 21 further includes a second binder, which includes at least one selected from polyacrylate, polyacrylic acid, polyacrylate, polymethyl methacrylate, polyacrylonitrile, polyamide, or sodium carboxymethyl cellulose. These second binders are high-strength binders that can further enhance the bond strength between the active material layer 21 and the current collector 20. In some embodiments, the total mass percentage of the first binder and the second binder is 0.5% to 8% based on the total mass of the active material layer 21. If the total mass percentage of the first binder and the second binder is too small, it will affect their bonding performance; if the total mass percentage of the first binder and the second binder is too large, it will reduce the amount of active material in the active material layer 21, thereby reducing the energy density of the electrochemical device 100. In some embodiments, the mass ratio of the first binder to the second binder in the active material layer 21 is 1:10 to 10:1.

[0073] It should be understood that Figure 3 The particle sizes of the first active material particles 3011, the second active material particles 3012, and the third active material particles 3013 are merely exemplary and not intended to limit the scope of this application. For example, in some embodiments, active material particles 301 and / or first binder particles 302 that do not constitute particle group 30 may be present in the active material layer 21. In some embodiments, the first binder particles 302 bind at least three active material particles 301. It should be understood that... Figure 3 The active material layer 21 located on one side of the current collector 20 is shown only schematically to illustrate the embodiment. The number, shape, and size of the active material layer 21 are not intended to limit this application.

[0074] In some embodiments, the microstructure of the active material layer in the thickness direction can be observed and tested using scanning electron microscopy (SEM) to determine the distribution of active material particles and binder particles. For example, this includes the number of active material particles bonded to a single first binder particle, the particle size and ratio of the first, second, and third active material particles, and the ratio of the edge of the first active material particle's cross-section to the length bonded to the first binder particle to the perimeter of the first active material particle's cross-section. It should be understood that this is merely exemplary, and other commonly used methods may also be employed.

[0075] Embodiments of this application also provide electronic devices including the electrochemical device 100 described above. The electronic devices in the embodiments of this application are not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0076] The following specific embodiments and comparative examples are provided to better illustrate this application, wherein a lithium-ion battery is used as an example. For ease of explanation, polyolefin is used in the active material layer of the positive electrode 10. Those skilled in the art will readily know or be able to know that when such a structure is used in the active material layer of the negative electrode 12, the same effect can be obtained as when polyolefin is used in the active material layer of the positive electrode 10.

[0077] Example 1

[0078] Preparation of the positive electrode 10: The positive electrode active material is lithium cobalt oxide, the conductive agent is conductive carbon black particles, the first binder is polypropylene, the second binder is sodium polyacrylate, and the positive electrode current collector is aluminum foil. Lithium cobalt oxide, conductive carbon black, polypropylene, and sodium polyacrylate are dissolved in an N-methylpyrrolidone (NMP) solution in a weight ratio of 97:1:1:1 to form a positive electrode slurry. The positive electrode slurry is coated onto the aluminum foil to obtain the active material layer. After drying, cold pressing, and cutting, the positive electrode 10 is obtained.

[0079] Preparation of negative electrode sheet 12: The positive electrode active material is graphite, the conductive agent is sodium carboxymethyl cellulose (CMC), the binder is styrene-butadiene rubber, and the negative electrode current collector is copper foil. Graphite, sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber are dissolved in deionized water at a weight ratio of 97.7:1.3:1 to form an active material slurry. A 10 μm thick copper foil is used as the negative electrode current collector, and the negative electrode slurry is coated onto the current collector at a coating amount of 9.3 mg / cm². 2 After drying and cutting, negative electrode sheet 12 is obtained.

[0080] Preparation of the separator 11: The substrate of the separator 11 is 8μm thick polyethylene (PE). A 2μm thick alumina ceramic layer is coated on each side of the substrate of the separator 11. Finally, 2.5mg of polyvinylidene fluoride (PVDF) adhesive is coated on each side of the ceramic layer and then dried.

[0081] Preparation of electrolyte: Under an environment with a water content of less than 10 ppm, LiPF6 was added to a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC), acrylate: vinylene carbonate (VC) = 20:30:20:28:2, by weight), with a LiPF6 concentration of 1.15 mol / L. The mixture was stirred evenly to obtain the electrolyte.

[0082] Preparation of lithium-ion batteries: Positive electrode 10, separator 11, and negative electrode 12 are stacked sequentially, with separator 11 positioned between the positive and negative electrode 10 for isolation. The electrode assembly 1 is then wound to obtain the electrode assembly 1. The electrode assembly 1 is placed in an outer aluminum-plastic film, and after dehydration at 80°C, the electrolyte is injected and the assembly is sealed. Following formation, degassing, and edge trimming processes, a lithium-ion battery is obtained.

[0083] The examples and comparative examples are based on the steps of Example 1 with parameter changes. The specific parameters that have been changed are shown in the table below.

[0084] In Examples 2 to 4, the mass percentage of polypropylene particles and sodium polyacrylate particles in the active material layer differed from those in Example 1.

[0085] In Comparative Example 1, the adhesive used was not polypropylene and sodium polyacrylate, but rather 2% polyvinylidene fluoride by mass. In Comparative Example 2, the adhesive used was not polypropylene, but rather 2% sodium polyacrylate by mass.

[0086] In Examples 5 to 7 and Comparative Examples 3 and 4, the particle size range of the polypropylene particles differed from that in Example 1.

[0087] In Examples 8 to 10 and Comparative Examples 5 and 6, the particle size range of the active material lithium cobalt oxide particles differed from that in Example 1. The test methods for each parameter of this application are described below.

[0088] Methods for testing particle size:

[0089] Sampling: Disassemble the electrochemical device 100 (e.g., lithium-ion battery), remove the electrode, and soak it in dimethyl carbonate (DMC) solution for 6 hours to remove residual electrolyte. Finally, dry the electrode in a drying oven. Sample preparation: Cut the test section, i.e., the cross-section of the active material layer along the thickness direction, from the dried electrode with a blade. Adhere the test sample to paraffin wax using a heating plate, and polish the test section with an ion polisher IB-195020CCP until the surface is smooth to obtain the SEM test sample. Testing: Observe the microstructure of the active material layer in the thickness direction using a scanning electron microscope JEOL6390.

[0090] Test method for bond strength between active material layer and current collector:

[0091] The positive electrode 10 was removed from the lithium-ion battery and allowed to air dry naturally for 1 hour. A test sample, 30 mm wide and 150 mm long, was then taken using a blade and fixed onto the test fixture of a high-speed rail tensile testing machine to test its bonding strength. The peel angle was 90 degrees, the tensile speed was 50 mm / min, and the tensile displacement was 60 mm. When the peel interface consists of the current collector and the active material layer, the measured result represents the bonding strength between the active material layer and the current collector.

[0092] Test method for compaction density (PD):

[0093] Take the cold-pressed positive electrode sheet 10, and use 1540.25mm... 2 Six positive electrode active material layers and six positive electrode current collectors were punched out using a mold. The total weight of the six positive electrode active material layers (Mc g) and the total weight of the six current collectors (Mb g) were weighed using an analytical balance (Shanghai Jingke Tianmei Electronic Balance FA2004B). The average thickness of the six positive electrode active material layers (Dc mm) and the average thickness of the six current collectors (Db mm) were measured using a micrometer. PD = [(Mc-Mb) / 6] / (Dc-Db) / 1540.25*1000, in g / ml.

[0094] Methods for testing energy density:

[0095] Place the lithium-ion battery in a 25°C constant temperature chamber and let it stand for 30 minutes to allow it to reach a constant temperature. Charge the battery at a constant current of 0.5C to a voltage of 4.45V, then charge it at a constant voltage of 4.45V to a current of 0.05C, and finally discharge it at 0.5C to a voltage of 3.0V. Record the discharge energy.

[0096] Table 1 shows the parameters and evaluation results for Examples 1 to 5 and Comparative Examples 1 to 2.

[0097] Table 1

[0098]

[0099]

[0100] Comparing Examples 1 to 4 and Comparative Examples 1 to 2, it is evident that when the binder for the active material layer is polyvinylidene fluoride (PVDF), the bond strength between the active material layer and the current collector is very weak. If the binder is replaced with high-adhesion polyacrylic acid, the bond strength between the active material layer and the current collector is significantly improved, but the compaction density is significantly reduced, resulting in a severe decrease in the energy density of the electrochemical device 100. After using polyolefin polypropylene (PP) in the active material layer, the bond strength between the active material layer and the current collector is improved, and the energy density of the electrochemical device 100 does not suffer a significant loss. Furthermore, the higher the proportion of polypropylene in the binder, the more significant the improvement in the compaction density of the positive electrode 10 and the energy density of the electrochemical device 100. Figure 4 and Figure 5 Scanning electron microscope (SEM) images of the active material layer of the positive electrode 10 in Examples 1 and 4 are shown, respectively. Furthermore, the increase in total binder content allows for an increase in the compaction density of the positive electrode 10 without brittleness, thereby improving the energy density of the electrochemical device 100.

[0101] Table 2 shows the parameters and evaluation results for Examples 1, 5 to 7 and Comparative Examples 3 to 4.

[0102] Table 2

[0103]

[0104]

[0105] Comparative Examples 1, 5 to 7, and Comparative Examples 3 to 4 show that as the particle size of polypropylene particles decreases, the number of active material particles bonded around a single polypropylene particle decreases, thus reducing the bonding efficiency of the active material lithium cobalt oxide particles. When the particle size of polypropylene particles is less than 0.1 μm, the number of active material lithium cobalt oxide particles bonded around a single polypropylene particle is less than three, resulting in a significant decrease in the bonding strength between the active material layer and the current collector. When the particle size of polypropylene particles is greater than 3.5 μm, the polypropylene particles are too large to efficiently fill the pores between the active material lithium cobalt oxide particles, and they themselves will create pores with the active material lithium cobalt oxide particles. Therefore, the effective bonding area of ​​the polypropylene particles decreases, the bonding strength between the active material layer and the current collector decreases, and the electrode thickness also increases, resulting in a decrease in the energy density of the electrochemical device 100. Further preferably, the particle size of the polypropylene particles is 0.5 μm to 1 μm, in which case at least three active material particles are bonded around a single polypropylene particle.

[0106] Table 3 shows the parameters and evaluation results for Examples 1, 8 to 10 and Comparative Examples 5 to 6.

[0107] Table 3

[0108]

[0109]

[0110] By comparing Examples 1, 8 to 10 and Comparative Examples 5 to 6, it can be seen that as the particle size of the active material lithium cobalt oxide particles increases, or the particle size range of the active material lithium cobalt oxide particles decreases, the packing efficiency between the active material lithium cobalt oxide particles decreases, the porosity between the active material lithium cobalt oxide particles increases, the number of active material lithium cobalt oxide particles bonded around a single polypropylene particle decreases, and the ratio of the edge of the cross-section of the largest first active material particle to the length bonded to the polypropylene particle to the perimeter of the cross-section of the first active material particle decreases, thus reducing the bonding strength of the active material lithium cobalt oxide particles. Furthermore, the increased packing porosity leads to a decrease in the volume utilization rate of the active material layer, thereby reducing the energy density of the electrochemical device 100.

[0111] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of disclosure in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by any combination of the above-described technical features or their equivalents. For example, technical solutions formed by substituting the above-described features with technical features having similar functions disclosed in this application.

Claims

1. An electrode sheet, comprising: current collector; as well as An active material layer located on the current collector; The active material layer comprises multiple particle groups, each particle group containing a first binder particle and at least three active material particles bonded together by the first binder particle. The particle size of the first binder particle in the plurality of particle groups is 0.1 μm to 2 μm; The particle size of the active material particles in the plurality of particle groups is 2 μm to 20 μm; The at least three active material particles include a first active material particle, a second active material particle, and a third active material particle. The particle size of the first active material particle in the plurality of particle groups is larger than that of the second active material particle, and the particle size of the second active material particle in the plurality of particle groups is larger than that of the third active material particle. The ratio of the length of the edge of the cross-section of the first active material particle bonded to the first adhesive particle to the perimeter of the cross-section of the first active material particle is 0.05 to 0.

2.

2. The electrode according to claim 1, wherein, The particle size of the first binder particle in the plurality of particle groups is 0.3-1.5 μm.

3. The electrode according to claim 1, wherein, The first binder particles contain polyolefins.

4. The electrode according to claim 3, wherein, The polyolefin includes at least one of polypropylene or polyethylene.

5. The electrode according to claim 1, wherein, The particle size of the first active material particle in the plurality of particle groups is 4 μm to 17 μm larger than the particle size of the second active material particle in the plurality of particle groups. The ratio of the particle size of the first active material particle in the plurality of particle groups to the particle size of the second active material particle in the plurality of particle groups is 2:1 to 7:

1. The particle size of the second active material particle in the plurality of particle groups is 0.01 μm to 8 μm larger than the particle size of the third active material particle in the plurality of particle groups. Furthermore, the ratio of the particle size of the second active material particle in the plurality of particle groups to the particle size of the third active material particle in the plurality of particle groups is greater than 1 and less than or equal to 4.

6. The electrode according to claim 1, wherein, The active material layer further includes a second binder, the composition of which includes at least one of polyacrylate, polyacrylic acid, polyacrylate, polymethyl methacrylate, polyacrylonitrile, polyamide or sodium carboxymethyl cellulose.

7. The electrode according to claim 6, wherein, Based on the total mass of the active material layer, the percentage of the total mass of the first binder particles and the second binder is 0.5% to 8%, and the mass ratio of the first binder particles to the second binder is 1:10 to 10:

1.

8. An electrochemical device comprising a positive electrode, a negative electrode, and a separating membrane disposed between the positive electrode and the negative electrode, wherein, At least one of the positive electrode and the negative electrode is an electrode according to any one of claims 1 to 7.

9. An electronic device comprising the electrochemical device according to claim 8.

Images