Anode pole piece, electrochemical device and electric equipment

Abstract

The invention discloses an anode plate, an electrochemical device and electric equipment, and belongs to the technical field of electrochemical energy storage. The anode pole piece comprises an anode current collector and an anode active material layer arranged on at least one surface of the anode current collector. The pore-forming conductive agent is introduced into the anode active material layer, the pore-forming conductive agent comprises the silica gel matrix and the carbon nanotubes, at least part of the carbon nanotubes are inserted into the silica gel matrix, and the pore-forming conductive agent has the characteristics of liquid absorption and high-temperature dehydration, so that the anode pole piece realizes self-liquid supply and self-pore-forming; an expansion space is provided for the anode active material, so that the reliability of battery circulation is ensured; the carbon nano tube in the pore-forming conductive agent can ensure the conductivity in the residual pores after the silica gel is dehydrated, and the cutoff phenomenon is prevented.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, specifically to an anode plate, an electrochemical device, and an electrical device. Background Technology

[0002] With the development of the consumer market, the requirements for energy density of electrochemical devices (such as lithium-ion batteries) are becoming increasingly stringent. The anode plates of lithium-ion batteries have been switched from pure graphite systems to silicon-doped systems. Due to the high expansion characteristics of silicon materials, silicon-doped anode plates are prone to problems such as active material pulverization and current collector breakage.

[0003] To address these issues, the current mainstream approach is to optimize the type and high binder content of the binder in the anode active material layer to reduce the expansion of the silicon-doped system. However, the development of new binder materials is slow, and the anode slurry formulation with high binder content is difficult to process, resulting in a low yield of anode sheets.

[0004] Therefore, there is an urgent need to develop an anode electrode that can provide expansion space for the anode active material during the charging and discharging process. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of existing technologies and provide an anode electrode, an electrochemical device, and an electrical device. This application introduces a pore-forming conductive agent into the anode active material layer. The pore-forming conductive agent comprises a silica matrix and carbon nanotubes, with at least a portion of the carbon nanotubes intercalating within the silica matrix. This pore-forming conductive agent possesses liquid absorption and high-temperature dehydration properties, enabling the anode electrode to achieve self-supply and self-pore formation, providing expansion space for the anode active material, thereby ensuring the reliability of battery cycling. The carbon nanotubes in the pore-forming conductive agent ensure conductivity within the residual pores after silica dehydration, preventing current interruption.

[0006] To achieve the above objectives, in a first aspect of this application, an anode electrode is provided, comprising an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector. The anode active material layer comprises an anode active material and a pore-forming conductive agent, wherein the mass ratio of the pore-forming conductive agent to the anode active material is (1~10):100. The pore-forming conductive agent comprises a silicone matrix and carbon nanotubes, wherein at least a portion of the carbon nanotubes are intercalated within the silicone matrix.

[0007] Preferably, the mass ratio of the pore-forming conductive agent to the anodic active material is (2~5):100.

[0008] Preferably, the mass ratio of silicone to conductive agent in the silicone-coated conductive agent is (0.1~5):1, and more preferably (0.5~2):1.

[0009] Preferably, the average particle size of the silicone matrix is ​​0.5~5μm, and more preferably 1~3μm.

[0010] Preferably, the carbon nanotubes include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and oligo-walled carbon nanotubes; Preferably, the outer diameter of the carbon nanotube is 1~50 nm; Preferably, the average length of the carbon nanotubes is 0.1~10μm.

[0011] Preferably, the porosity of the anolyte active material layer is 10-20%.

[0012] Preferably, the mass percentage of the anodic active material in the anodic active material layer is 90-99%.

[0013] Preferably, the anode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate.

[0014] Preferably, the anodic active material layer further includes a first conductive agent and a first binder, wherein the mass of the anodic active material, the first conductive agent and the first binder is (90~99):(0.5~1):(0.5~1).

[0015] In a second aspect of this application, an electrochemical device is provided, including the anode electrode provided in the first aspect of this application.

[0016] Preferably, the electrochemical device further includes a cathode electrode and a diaphragm, the diaphragm being disposed between the anode electrode and the cathode electrode.

[0017] In a third aspect of this application, an electrical device is provided, including the electrochemical device provided in the second aspect of this application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the anode electrode provided in this application after liquid absorption; Figure 2 This is a schematic diagram of the anode plate provided in this application after liquid removal.

[0019] In the figure, 1 is the anode current collector, 2 is the cathode active material layer, 3 is the silica matrix, and 4 is the carbon nanotube. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0022] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0023] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0024] In a first aspect of this application, an anode electrode is provided, comprising an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector. The anode active material layer comprises an anode active material and a pore-forming conductive agent, wherein the mass ratio of the pore-forming conductive agent to the anode active material is (1~10):100. The pore-forming conductive agent comprises a silicone matrix and carbon nanotubes, wherein at least a portion of the carbon nanotubes are intercalated within the silicone matrix.

[0025] This application introduces a pore-forming conductive agent into the anode active material layer. The pore-forming conductive agent comprises a silica matrix and carbon nanotubes, with at least a portion of the carbon nanotubes intercalating within the silica matrix. This pore-forming conductive agent has the characteristics of liquid absorption and high-temperature dehydration, enabling the anode electrode to achieve self-supply and self-pore-forming functions, providing expansion space for the anode active material, thereby ensuring the reliability of battery cycle. The carbon nanotubes in the pore-forming conductive agent can ensure the conductivity of the residual pores after silica dehydration, preventing current interruption.

[0026] This application can reasonably control the pore size in the anode active material layer by adjusting the mass ratio of the pore-forming conductive agent to the anode active material. This can avoid the inability to effectively create pores due to insufficient pore-forming conductive agent, and also avoid the disconnection of electrode ion conduction and lithium deposition caused by excessively large pores in the anode active material layer.

[0027] The inventors discovered through research that the mechanism by which the anode electrode of this application achieves self-supply of liquid and self-forming of pores is as follows: During the preparation of the anode electrode, a pore-forming conductive agent is introduced into the anode slurry. This agent absorbs moisture from the slurry, causing the particles to expand (liquid absorption swelling ratio 20-30%). The anode slurry containing the pore-forming conductive agent can then be coated onto the anode current collector to form an anode slurry coating. After the coating and drying process, the pore-forming conductive agent particles begin to dehydrate, leaving uniformly distributed gaps within the anode active material layer. At this point, the pore-forming conductive agent in the coating... Figure 2 As shown.

[0028] In the fabrication of secondary batteries, the anode electrode, separator, and cathode electrode are sequentially stacked and wound, then encapsulated, injected with electrolyte, and resealed to obtain the battery cell. During electrolyte injection, the pore-forming conductive agent particles can reabsorb electrolyte to fill the gaps (e.g., Figure 1 As shown), this effectively increases the electrolyte retention of the battery cell. During battery cell cycling, the cycle preferentially consumes the free electrolyte in the core and casing. When the electrolyte is insufficient, due to the temperature rise and compression during battery cell cycling, the electrolyte absorbed by the pore-forming conductive agent particles can be released, providing electrolyte in a timely manner to ensure the electrolyte required for battery cell cycling. After the electrolyte is released from the pore-forming conductive agent particles, it can reform pores in the anode active material layer (such as...). Figure 2 As shown in the figure, the newly formed pores can be used to provide a buffer space for electrode expansion, while the carbon nanotubes loaded with the pore-forming conductive agent particles can maintain electrical connection with the normal area of ​​the electrode, thus synergistically ensuring the cycle performance of the battery cell.

[0029] For example, the mass ratio of the pore-forming conductive agent to the anodic active material can be 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100 or 10:100, or within any two of the above mass ratios.

[0030] In some embodiments, the mass ratio of the pore-forming conductive agent to the anodic active material is (2~5):100.

[0031] In some embodiments, the mass ratio of the silicone matrix to the carbon nanotubes in the pore-forming conductive agent is (0.1~5):1.

[0032] In some embodiments, the mass ratio of the silicone matrix to carbon nanotubes in the pore-forming conductive agent is (0.5~2):1.

[0033] In some embodiments, the average particle size of the silicone matrix is ​​0.5~5μm, more preferably 1~3μm.

[0034] For example, the average particle size of the silicone matrix may be 0.5μm, 1μm, 2μm, 3μm, 4μm or 5μm, or within the range of any two of the above values.

[0035] In some embodiments, the carbon nanotubes include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and oligo-walled carbon nanotubes. In some embodiments, the outer diameter of the carbon nanotube is 1~50 nm; the average length of the carbon nanotube is 0.1~10 μm.

[0036] For example, the outer diameter of the carbon nanotube can be 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, or within the range of any two of the above values.

[0037] The average length of the carbon nanotubes can be 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, or fall within the range of any two of the above values.

[0038] In some embodiments, the porosity of the anodic active material layer is 10-20%.

[0039] For example, the porosity of the anodic active material layer may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, or fall within the range of any two of the above values.

[0040] In some embodiments, the pore-forming conductive agent can be prepared by the following preparation method: Hydrophilic silica gel and carbon nanotubes are added to a surfactant solution and mixed to obtain a mixture. The mixture is then granulated and dried to obtain a pore-forming conductive agent.

[0041] In some embodiments, the surfactant in the surfactant solution includes at least one of sulfonate surfactants, sulfate surfactants, and phosphate surfactants. The sulfonate surfactant may include at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, and sodium α-alkenyl sulfonate. The sulfate surfactant may include at least one of sodium dodecyl sulfate and sodium fatty alcohol polyoxyethylene ether sulfate. The phosphate surfactant may include at least one of potassium dodecyl phosphate, sodium bis(2-ethylhexyl) phosphate, and lauryl ether-3-phosphate triethanolamine salt.

[0042] In some embodiments, the hydrophilic silica gel may be at least one of chemically modified silica gel and physically blended modified silica gel.

[0043] The chemically modified silica gel includes, but is not limited to, at least one of polyether-modified silica gel, hydroxyl-modified silica gel, carboxyl-modified silica gel, and amino-modified silica gel; the physically blended modified silica gel includes, but is not limited to, at least one of nano-silica blended modified silica gel and surfactant blended modified silica gel, wherein the surface of nano-silica gel is rich in silanol groups, and when blended with silica gel, the resulting nano-silica blended modified silica gel has a certain degree of hydrophilicity; the surfactant in the surfactant blended modified silica gel can be anionic surfactant, such as at least one of sulfonate surfactants, sulfate surfactants, phosphate ester surfactants, and phosphate ester surfactants.

[0044] In some embodiments, the mass ratio of the hydrophilic silica gel to the carbon nanotubes is (0.1~5):1.

[0045] For example, the mass ratio of the hydrophilic silica gel to the carbon nanotubes can be 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1 or 5:1, or fall within the range of any two of the above mass ratios.

[0046] In some embodiments, the mass ratio of the hydrophilic silica gel to the carbon nanotubes is (0.5~2):1.

[0047] In some embodiments, the anode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate.

[0048] The graphite may include at least one of artificial graphite, natural graphite, and modified graphite; the silicon-based material may be selected from at least one of elemental silicon, silicon oxide, silicon-carbon composite, and silicon alloy; the tin-based material may be selected from at least one of elemental tin, tin oxide, and tin alloy.

[0049] In some embodiments, the anodic active material layer further includes a first conductive agent and a first binder, wherein the mass of the anodic active material, the first conductive agent and the first binder is (90~99):(0.5~1):(0.5~1).

[0050] The first conductive agent includes at least one of carbon nanotubes, acetylene black, carbon black, Ketjen black, carbon dots, graphene, and carbon nanofibers.

[0051] In some embodiments, the first adhesive includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, polyamide, polyimide, and polyethyleneimine.

[0052] In some embodiments, the anode current collector is typically a structure or component that collects current. The anode current collector can be any material suitable for use as an anode current collector in a secondary battery. For example, the anode current collector can be, but is not limited to, metal foil, and more specifically, copper foil.

[0053] In a second aspect of this application, an electrochemical device is provided, including the anode electrode provided in the first aspect of this application.

[0054] In some embodiments, the electrochemical device includes any apparatus in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy, and specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0055] In some embodiments, the electrochemical device further includes a cathode electrode and a diaphragm disposed between the anode electrode and the cathode electrode.

[0056] In some embodiments, the cathode electrode includes a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector, the cathode active material layer including a cathode active material, a second conductive agent and a second binder.

[0057] Based on the total mass of the cathode active material layer, the mass percentage of the cathode active material is 90-99%, the mass percentage of the second conductive agent is 0.5-5%, and the mass percentage of the binder is 0.5-5%. For example, in the cathode active material layer, the mass percentage of the cathode active material can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, or within any two of the above values; the mass percentage of the second conductive agent can be 0.5%, 1%, 2%, 3%, 4%, or 5%, or within any two of the above values; and the mass percentage of the binder can be 0.5%, 1%, 2%, 3%, 4%, or 5%, or within any two of the above values.

[0058] The second adhesive includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, polyamide, polyimide, and polyethyleneimine.

[0059] The second conductive agent includes at least one of carbon nanotubes, acetylene black, carbon black, Ketjen black, carbon dots, graphene, and carbon nanofibers.

[0060] The cathode current collector is typically a structure or component that collects current. The cathode current collector can be any material suitable for use as a cathode current collector in a secondary battery. For example, the cathode current collector can be, but is not limited to, metal foil, and more specifically, aluminum foil.

[0061] This application does not impose any particular restrictions on the material and shape of the diaphragm, as long as it does not significantly impair the effectiveness of this application.

[0062] In some embodiments, the diaphragm comprises a porous sheet-like or non-woven material with excellent liquid retention properties. The materials for the resin or glass fiber diaphragm include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, and polyethersulfone. The polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The materials for the above-mentioned diaphragms can be used alone or in any combination.

[0063] In some embodiments, the electrochemical device may include an outer packaging that can be used to encapsulate the cathode electrode, anode electrode, diaphragm, and electrolyte.

[0064] The outer packaging of the electrochemical device can be a hard shell or a soft shell. The hard shell can be a hard plastic shell, an aluminum shell, a steel shell, etc. The soft package can be a pouch-type soft package. The material of the soft package can be plastics such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0065] In some embodiments, the electrolyte may include at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte.

[0066] In some embodiments, the liquid electrolyte may include a non-aqueous solvent and a lithium salt.

[0067] In some embodiments, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate.

[0068] In some embodiments, the non-aqueous solvent may be at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0069] The carbonate compound may include at least one of chain carbonate compounds, cyclic carbonate compounds, and fluorocarbonate compounds.

[0070] The chain carbonate compound may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and methyl ethyl carbonate (MEC).

[0071] The cyclic carbonate compound may include at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), and vinyl ethylene carbonate (VEC).

[0072] The fluorocarbonate compound may include at least one of 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, and trifluoromethylethylene carbonate.

[0073] The carboxylic acid ester compound may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonate lactone, caprolactone, and methyl formate.

[0074] The ether compound may include at least one of propylene glycol propyl ether (PP), ethylene glycol n-propyl ether (EP), dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0075] In some embodiments, the non-aqueous solvent may also include at least one of 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.

[0076] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5~2 mol / L.

[0077] In some embodiments, the additive includes at least one selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfate (DTD), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) borate (TMSB), lithium difluorophosphate (LiDFOP), trimethyl phosphate (TMP), triphenyl phosphate (TPP), propylene sulfite (PS), vinyl ethylene carbonate (VEC), and 1,3-propanesulfonate lactone (1,3-PS).

[0078] In some embodiments, the additive has a mass percentage of 0.5 to 10% based on the total mass of the electrolyte.

[0079] For example, the mass percentage of the additive in the electrolyte may be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, or fall within the range of any two of the above values.

[0080] In a third aspect of this application, an electrical device is provided, including the electrochemical device provided in the second aspect of this application.

[0081] The inventors conducted numerous research experiments during the research process, including designing and fabricating different secondary batteries and testing their performance. Some of the experimental examples and test results are listed below to illustrate this application: Example 1 A method for preparing a secondary battery includes the following steps: S1. Preparation of the anode electrode: S11. Select commercially available carbon nanotubes with a diameter of 50 nm and an average length of 10 μm. Add hydrophilic silica gel and carbon nanotubes to a 0.5 mol / L surfactant aqueous solution and mix them evenly to obtain a mixture. Spray granulate and dry the mixture to obtain a pore-forming conductive agent. The types of hydrophilic silica gels and surfactants are shown in Table 1. The mass ratio of hydrophilic silica to carbon nanotubes and the mass percentage of surfactant in hydrophilic silica are shown in Table 1. S12. After thoroughly mixing the anode active material, pore-forming conductive agent, binder polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in deionized water solvent, an anode slurry is obtained. The anode active material is a mixture of graphite and SiC in a 3:1 mass ratio. The mass ratio of the anode active material and the pore-forming conductive agent is shown in Table 1. The mass ratio of anode active material + pore-forming conductive agent: PAA:CMC:SBR = 95:2:2:1. The anode slurry is coated on two opposite surfaces of the current collector copper foil, dried at 85°C, cold-pressed, then trimmed and slit, dried under vacuum at 85°C for 12 hours, and the tabs are welded to obtain the anode electrode sheet. The compaction density of the coating on the anode electrode sheet is 1.65 g / cm³. 3 ; S2. Preparation of the cathode electrode: LiCoO2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in N-methylpyrrolidone solvent (NMP) at a mass ratio of 97:2:1 to obtain a cathode slurry. The cathode slurry was coated onto two opposing surfaces of a current collector aluminum foil, dried at 85°C, cold-pressed, trimmed, and slit. After drying under vacuum at 85°C for 6 hours, tabs were welded to obtain the cathode electrode. The compacted density of the coating on the anode electrode was 4.2 g / cm³. 3 .

[0082] S3. Preparation of the separating membrane: Polyethylene (PE) porous polymer film is used as the separator.

[0083] S4. Preparation of electrolytes: Ethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), propylene glycol propyl ether (PP), and ethylene glycol n-propyl ether (EP) were mixed in a volume ratio of EC:PC:DEC:PP:EP = 20:15:15:30:20, and fully dried lithium salt LiPF6 was added to prepare an electrolyte with a LiPF6 concentration of 1 mol / L.

[0084] S5. Preparation of pouch secondary batteries: The prepared cathode electrode, separator, and anode electrode are stacked in sequence, with the separator positioned between the cathode and anode electrodes, and wound to obtain a bare battery cell. The battery cell is designed to have a capacity of 800mAh and a voltage range of 3.0-4.55V. The bare battery cell is placed in an aluminum-plastic film outer packaging for sealing, and then placed in an 80℃ vacuum oven for baking for 15 hours. Electrolyte is injected into the dried battery with an injection coefficient of 1.8g / Ah. The battery is then sealed, allowed to stand, formed, and then resealed and tested for capacity to obtain the secondary battery.

[0085] Examples 2-5 The difference between Examples 2-5 and Example 1 is that Examples 2-5 change the mass ratio of hydrophilic liquid silica gel to carbon nanotubes in step S11, as detailed in Table 1.

[0086] Examples 6-10 The difference between Examples 6-10 and Example 1 is that Examples 6-10 changed the mass ratio of the pore-forming conductive agent to the anode active material in step S12, as detailed in Table 1.

[0087] Examples 12-15 The difference between Examples 12-15 and Example 1 is that Examples 12-15 changed the type of hydrophilic silica gel and / or the type of surfactant in step S11, as detailed in Table 1.

[0088] Examples 16-19 The difference between Examples 16-19 and Example 1 is that Examples 16-19 changed the percentage of surfactant mass in hydrophilic silica in step S11. By adjusting the process parameters during granulation, the average particle size of the silica matrix in the pore-forming conductive agent was changed, as detailed in Table 2.

[0089] Examples 20-21 The difference between Examples 20 and 21 and Example 1 is that Examples 20 and 21 change the compaction density of the coating on the anode sheet by adjusting the pressure and number of cold pressing steps in step S12, as detailed in Table 2.

[0090] Comparative Example 1 The difference between this comparative example and Example 1 is that in this comparative example, step S11 is as follows: carbon nanotubes are added to a surfactant solution and mixed evenly, then dried to obtain a pore-forming conductive agent, so that the obtained pore-forming conductive agent does not contain silica gel, as detailed in Table 2.

[0091] Comparative Examples 2-3 The difference between Comparative Examples 2 and 3 and Example 1 is that Comparative Examples 2 and 3 changed the mass ratio of the pore-forming conductive agent to the anodic active material in step S12, as shown in Table 2.

[0092] Performance testing The performance of the anode and secondary battery in the above embodiments and comparative examples was tested using the following methods: (1) Porosity of the anodic active material layer: tested by BET method.

[0093] (2) Average particle size of the silica matrix in the anodic active material layer: tested by a laser particle size analyzer.

[0094] (3) Liquid retention: When preparing secondary batteries, record the mass of electrolyte used for cell forming and the design capacity of the cell, and calculate the liquid retention according to the following formula: Liquid retention = Mass of electrolyte used for cell forming / Design capacity of cell.

[0095] (4) Cycle performance: Several secondary batteries prepared in each example and comparative example were taken and tested at 25°C according to the following steps: ① Charging steps: Charge the secondary battery at a constant current rate of 2C to 4.2V, at a constant current rate of 1.5C to 4.35V, at a constant current rate of 1C to 4.55V, and at a constant voltage until the current is below 0.05C. ② Discharge steps: Discharge the secondary battery at a constant current rate of 0.7C to 3.0V; ③ Repeat the charging step ① and discharging step ②; Record the thickness T0 of the secondary battery after the first charging step and the thickness T of the secondary battery after 500 cycles, and calculate the thickness expansion rate λ of the secondary battery: λ=(T-T0) / T0×100; During the above cycle, the discharge capacity of the first cycle and the discharge capacity of the 500th cycle are recorded, and the capacity retention rate of the secondary battery is calculated: Discharge capacity retention rate = Discharge capacity of the 500th cycle / Discharge capacity of the first cycle × 100%; Every 50 cycles, a secondary battery is taken out and disassembled to obtain the anode plate. The surface of the anode plate is manually observed for abnormal phenomena such as lithium plating until an abnormality is observed on the surface of the anode plate. The maximum number of cycles that the secondary battery can achieve to maintain the anode plate interface without abnormality is recorded.

[0096] The test results are shown in Table 3 below.

[0097] Table 1 Table 2 In Tables 1-2, S represents the example and D represents the comparative example; The hydroxyl-modified silicone is from Guangzhou Silok New Materials Co., Ltd., model number Silok886H; The carboxyl-modified silica gel is 3-carboxypropyl-functionalized silica gel (569836 - 25G) provided by Sigma-Aldrich (Shanghai) Trading Co., Ltd. The amino-modified silica gel is from Ba Shifu (Shanghai) Biomedical Technology Co., Ltd., and its brand name is Silica gel110 NH2.

[0098] Table 3 As can be seen from Tables 1-3, the embodiments of this application introduce a pore-forming conductive agent into the anode active material layer. The pore-forming conductive agent includes a silica matrix and carbon nanotubes, with at least a portion of the carbon nanotubes intercalating inside the silica matrix. This can improve the reliability of the secondary battery cycle while ensuring the liquid retention of the secondary battery, making the liquid retention of the secondary battery not less than 1.42 g / mAh, the discharge capacity retention rate after 500 cycles not less than 78.3%, the thickness expansion rate not higher than 14.2%, and the interface of the anode electrode without any abnormal phenomena.

[0099] Compared with Example 1, the pore-forming conductive agent in Comparative Example 1 does not contain silicone, which significantly reduces the liquid retention of the secondary battery and the cycle stability of the secondary battery. Compared with Example 1, the mass ratio of pore-forming conductive agent to anode active material in Comparative Example 2 was too small, which reduced the liquid retention of the secondary battery and significantly decreased the cycle stability of the secondary battery.

[0100] Compared with Example 1, the mass ratio of pore-forming conductive agent to anode active material in Comparative Example 3 was too high, which significantly reduced the stability of the secondary battery cycle.

[0101] The embodiments of this application have been described in detail above. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. An anode electrode, characterized in that, The device includes an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector. The anode active material layer includes an anode active material and a pore-forming conductive agent. The mass ratio of the pore-forming conductive agent to the anode active material is (1~10):

100. The pore-forming conductive agent includes a silicone matrix and carbon nanotubes, with at least a portion of the carbon nanotubes intercalating inside the silicone matrix.

2. The anode plate as described in claim 1, characterized in that, The mass ratio of the pore-forming conductive agent to the anodic active material is (2~5):

100.

3. The anode plate as described in claim 1, characterized in that, The mass ratio of silicone to conductive agent in the silicone-coated conductive agent is (0.1~5):1, more preferably (0.5~2):

1.

4. The anode plate as described in claim 1, characterized in that, The average particle size of the silica matrix is ​​0.5~5μm, more preferably 1~3μm.

5. The anode plate as described in claim 1, characterized in that, The carbon nanotubes include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and oligo-walled carbon nanotubes. And / or, the outer diameter of the carbon nanotubes is 1~50 nm; And / or, the average length of the carbon nanotubes is 0.1~10 μm.

6. The anode plate as described in claim 1, characterized in that, The porosity of the anodic active material layer is 10-20%.

7. The anode plate as described in claim 1, characterized in that, The anodic active material layer further includes a first conductive agent and a first binder, wherein the mass of the anodic active material, the first conductive agent, and the first binder is (90~99):(0.5~1):(0.5~1). And / or, the anode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate.

8. An electrochemical device, characterized in that, Includes the anode electrode sheet as described in any one of claims 1 to 7.

9. The electrochemical device as described in claim 8, characterized in that, It also includes a cathode electrode and a diaphragm, the diaphragm being disposed between the anode electrode and the cathode electrode.

10. An electrical appliance, characterized in that, The electrochemical device includes any one of claims 8 to 9.

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