Silicon-based negative electrode material and preparation method thereof, negative electrode plate and preparation method thereof, solid-state battery and electric device

Abstract

The invention discloses a silicon-based negative electrode material and a preparation method thereof, a negative electrode plate and a preparation method thereof, a solid-state battery and an electric device, and relates to the technical field of batteries, the silicon-based negative electrode material comprises a silicon-based active substance, a fluorine-containing composite binder and a conductive agent, the fluorine-containing composite binder comprises a fluorine-containing copolymer and a fluorine-containing polymer; the fluorine content of the fluorine-containing copolymer is greater than or equal to 60%; and the elastic modulus of the fluorine-containing composite binder is 1.0 to 1.2 GPa. The fluorine content of the fluorine-containing copolymer is greater than or equal to 60%, and the fluorine-containing copolymer and F <-> in the electrolyte form a compact interface layer, so that electrolyte permeation can be inhibited, and the interface stability is improved. The elastic modulus of the fluorine-containing composite binder is 1.0-1.2 GPa, the fluorine-containing composite binder is matched with the expansion stress of the silicon-based active material, elastic buffer can be provided for the silicon-based negative electrode material, the expansion stress of the silicon-based negative electrode can be uniformly dispersed by forming a three-dimensional elastic cross-linked network, the generation of cracks is reduced, the fracture of a transmission channel is reduced, and the ion transmission performance is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a silicon-based negative electrode material, a preparation method thereof, a negative electrode sheet, a preparation method thereof, a solid-state battery and a power utilization device. BACKGROUND

[0002] In the development of next-generation high-energy-density solid-state batteries, silicon-based negative electrodes are considered as key materials for breaking through the bottleneck of existing graphite negative electrodes due to their ultra-high theoretical specific capacity (>1000 mAh / g). However, silicon-based materials face serious volume expansion (>300%) during charging and discharging, leading to problems such as electrode structure pulverization, intensified interface side reactions, increased gas production, and thus causing industrialization difficulties such as short battery cycle life (<1000 cycles), low energy efficiency (<97%), and high internal resistance (>3 mΩ). SUMMARY

[0003] The present application provides a silicon-based negative electrode material, a preparation method thereof, a negative electrode sheet, a preparation method thereof, a solid-state battery and a power utilization device to reduce the expansion of silicon-based batteries and improve the life of silicon-based batteries.

[0004] In a first aspect, the present application provides a silicon-based negative electrode material, comprising a silicon-based active material, a fluorine-containing composite binder and a conductive agent, wherein: The fluorine-containing composite binder comprises a fluorine-containing copolymer and a fluorine-containing polymer. The fluorine content of the fluorine-containing copolymer is greater than or equal to 60%. The elastic modulus of the fluorine-containing polymer is 0.8-1.0 GPa.

[0005] The present application can provide a large number of high-polarity fluorine chain segments by the fluorine content of the fluorine-containing copolymer being greater than or equal to 60%, which can form a dense interface layer (contact angle 125°, 1M LiPF6 / EC:DMC electrolyte test) through van der Waals forces and dipole interactions (bond energy ≈20-50 kJ / mol) with F - of the lithium fluoride salt, inhibit electrolyte penetration, improve interface stability and cycle life. The elastic modulus of the fluorine-containing polymer is 0.8-1.0 GPa, which can provide elastic buffering for the silicon-based negative electrode material, wherein the three-dimensional elastic cross-linked network formed can uniformly disperse the expansion stress of the silicon-based negative electrode, reduce the generation of cracks, reduce the fracture of transmission channels, maintain the stability of the transmission channels, and improve the ion transmission performance.

[0006] In some embodiments, the fluorine-containing copolymer comprises a first fluorine-containing substance and a second fluorine-containing substance, wherein: The mass ratio of the first fluorine-containing substance and the second fluorine-containing substance is (6-7):(3-4). The mass ratio of the first fluorine-containing substance and the second fluorine-containing substance in this range can make the modulus of the fluorine-containing copolymer be 1.0-1.2 GPa, match the expansion stress (8-12 MPa) of the silicon-based active material, and reduce the expansion of the silicon-based material; and / or, The first fluorine-containing substance includes at least one of polyvinylidene fluoride, polytetrafluoroethylene and polyperfluoro ether. The first fluorine-containing substance is selected to copolymerize with the second fluorine-containing substance to form a high-strength binder, thereby improving the modulus of the fluorine-containing copolymer; and / or, The second fluorine-containing substance includes at least one of HFP-VDF copolymer, TFE-P copolymer and hexafluoropropylene. The second fluorine-containing substance is selected to copolymerize with the first fluorine-containing substance to form a high-strength binder, thereby improving the modulus of the fluorine-containing copolymer; and / or, The fluorine-containing polymer includes at least one of fluorine-containing polyurethane and fluorinated elastomer. The fluorine-containing polymer contains elastic crosslinking groups, can realize dynamic stress buffering, and has a crosslinking degree > 70%, an elongation at break > 300%, and a modulus of 0.8-1.0 GPa. The fluorine-containing polymer can cooperate with the fluorine-containing copolymer to adapt to the expansion stress of the silicon negative electrode and reduce the expansion of the silicon-based material.

[0007] In some embodiments, the mass ratio of the fluorine-containing copolymer and the fluorine-containing polymer is (5-6):(4-5). The mass ratio of the fluorine-containing copolymer and the fluorine-containing polymer in this range can better cooperate to adapt to the expansion stress of the silicon negative electrode and reduce the expansion of the silicon-based material; and / or, The mass fraction of the fluorine-containing composite binder in the silicon-based negative electrode material is 2%-6%. The mass fraction of the fluorine-containing composite binder in the silicon-based negative electrode material in this range can reduce the occupation of the negative electrode active material, reduce the loss of energy density, and reduce the expansion of the silicon-based active material.

[0008] It should be noted that the silicon-based active substance includes but is not limited to at least one of SiOx / C composite material. The conductive agent includes but is not limited to at least one of carbon nanotube and graphene. The mass ratio of the silicon-based active substance, the fluorine-containing composite binder and the conductive agent is (88-95):(2-6):(2-6).

[0009] In a second aspect, the application provides a preparation method of a silicon-based negative electrode material, which is used to prepare the silicon-based negative electrode material of the first aspect, and includes the following steps: Mixing the fluorine-containing copolymer and the fluorine-containing polymer with a solvent to obtain fluorine-containing composite binder slurry; Mixing the silicon-based active substance, the conductive agent and the fluorine-containing composite binder slurry, and removing the solvent to obtain the silicon-based negative electrode material.

[0010] The fluorine-containing copolymer and the fluorine-containing polymer are mixed with the solvent to obtain a fluorine-containing composite binder slurry, so that the fluorine-containing copolymer and the fluorine-containing polymer can copolymerize in the solvent to form a high-strength binder, and the modulus, interfacial bonding energy and stress relaxation rate of the fluorine-containing composite binder are improved to adapt to the expansion stress of the silicon negative electrode.

[0011] In some embodiments, the stirring rate of the fluorine-containing copolymer and the fluorine-containing polymer mixed with the solvent is 1000-3000 rpm. Within this range, the fluorine-containing copolymer and the fluorine-containing polymer can quickly copolymerize in the solvent to form a high-strength binder; and / or, The temperature of the fluorine-containing copolymer and the fluorine-containing polymer mixed with the solvent is 40-60℃. Within this range, the fluorine-containing copolymer and the fluorine-containing polymer can quickly copolymerize in the solvent to form a high-strength binder; and / or, The temperature of the silicon-based active material, the conductive agent and the fluorine-containing composite binder slurry is 40-60℃. Within this range, the fluorine-containing composite binder can be uniformly dispersed in the slurry; and / or, The silicon-based active material, the conductive agent and the fluorine-containing composite binder slurry are mixed for 30-60 min. Within this range, the fluorine-containing composite binder can be uniformly dispersed in the slurry, and the viscosity of the slurry is stable at 5000±500 mPa·s (25℃).

[0012] In a third aspect, the present application provides a negative electrode sheet, comprising: a negative current collector; a negative active material layer arranged on at least one side of the negative current collector; and an interface modification layer arranged on the surface of the negative active material layer away from the negative current collector; The material of the negative active material layer comprises the silicon-based negative electrode material of the first aspect. The interface modification layer comprises a transmission layer and a gas adsorption layer, and the transmission layer is arranged between the gas adsorption layer and the negative active material layer.

[0013] The material of the negative electrode active material layer includes the silicon-based negative electrode material of the first aspect, which can reduce the expansion of the silicon-based negative electrode material, and the interface modification layer, the transmission layer and the gas adsorption layer on the surface of the negative electrode active material layer away from the negative electrode current collector. The transmission layer can improve the ion transmission capacity and the electron conduction capacity, and the adsorption layer can adsorb the gas generated by the silicon-based battery during use, reduce the expansion of the battery, and improve the overall performance of the silicon-based battery. The fluorine-containing composite binder in the silicon-based negative electrode material solves the mechanical mismatch problem of traditional silicon-based negative electrode active materials, and the interface modification layer solves the ion / electron transmission and gas generation problems, which realize the triple optimization of "mechanics-electrochemistry-gas generation".

[0014] In some embodiments, the transmission layer includes an ion transmission layer and an electron conduction layer, and the ion transmission layer is arranged between the electron conduction layer and the negative electrode active material layer. The material of the ion transmission layer includes at least one of fluorine aluminum lithium and lithium fluoride, and the material of the ion transmission layer can provide lithium ion migration number t ＋ ≥0.8, thereby improving the ion transmission performance, and its chemical stability, decomposition voltage >4.5V, which is beneficial to improve the stability of the silicon-based battery, and can also inhibit the dissolution of transition metals; and / or, The material of the electron conduction layer includes at least one of carbon nanotubes, silicon carbide nanowires and titanium carbide nanowires, which can reduce the electron impedance and improve the electron transmission efficiency, and the carbon nanotubes have stable performance in LiPF6 and less side reactions; and / or, The thickness of the ion transmission layer is 20-40nm, and the thickness of the ion transmission layer in this range can improve the ion transmission performance while reducing the occupation of the negative electrode active material layer and reducing the energy density loss; and / or, The thickness of the electron conduction layer is 150-250nm. The thickness of the electron conduction layer in this range can improve the electron transmission performance while reducing the occupation of the negative electrode active material layer and reducing the energy density loss.

[0015] In some embodiments, the material of the gas adsorption layer includes porous oxides and amino-containing polymers, and the porous oxides and amino-containing polymers have no side reactions with the positive electrode, stable performance, and strong CO2 adsorption capacity, and wherein: The amino-containing polymer includes at least one of polydopamine and polyaniline, and the amino-containing polymer can adsorb CO2, SO2 and HF; and / or, The porous oxide includes at least one of nano-Al2O3 and nano-SiO2, and the porous oxide can adsorb HF and neutralize acidic byproducts; and / or, The mass ratio of the amino-containing polymer to the porous oxide is (9~19):1. Within this range, the mass ratio balances chemical and physical adsorption capacities, resulting in a CO2 adsorption rate ≥90% and an HF adsorption rate ≥80%; and / or, The thickness of the gas adsorption layer is 10~30 nm. Within this range, the thickness of the gas adsorption layer can reduce the crowding of the negative electrode active material layer and reduce energy density loss while adsorbing and generating gas; and / or, The porosity of the gas adsorption layer is 30% to 50%. Within this range, the porosity of the gas adsorption layer can enhance the adsorption capacity for CO2 and HF gases, reduce gas production, and reduce battery expansion.

[0016] Fourthly, this application provides a method for preparing a negative electrode sheet, which includes the following steps: Fluorinated copolymers and fluoropolymers are mixed with solvents to obtain fluorinated composite adhesive slurry; A silicon-based active material, a conductive agent, and a fluorine-containing composite binder slurry are mixed to obtain a silicon-based anode material slurry. A silicon-based negative electrode material slurry is coated on at least one side of the negative electrode current collector and dried to obtain an electrode assembly containing a negative electrode active material layer. A transport layer and a gas adsorption layer are sequentially formed on the surface of the negative electrode active material layer to obtain the negative electrode sheet.

[0017] The negative electrode active material layer comprises the silicon-based negative electrode material described in the first aspect, which can reduce the expansion of the silicon-based negative electrode material. Simultaneously, on the surface of the negative electrode active material layer facing away from the negative electrode current collector, there are an interface modification layer, a transport layer, and a gas adsorption layer. The transport layer can improve ion transport and electron conduction capabilities, while the adsorption layer can adsorb gas generated during the use of the silicon-based battery, reducing battery expansion and improving the overall performance of the silicon-based battery. The fluorinated composite binder in the silicon-based negative electrode material solves the mechanical mismatch problem of traditional silicon-based negative electrode active materials, and the interface modification layer solves the ion / electron transport and gas generation problems. The two work synergistically to achieve a triple optimization of "mechanical-electrochemical-gas generation".

[0018] In some embodiments, in the process of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer, the drying step sequentially includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein: The initial temperature is 75~85℃. Within this range, the solvent can be gently removed, reducing the formation of microcracks; and / or, The initial removal time is 8-12 minutes; within this range, the solvent can be sufficiently removed; and / or, When the humidity at the first temperature is less than 10%, and the humidity is within this range, microcracks caused by solvent residue can be reduced, and / or... The second temperature is 95~105℃. Within this range, the crystallization of the fluorinated composite binder can be triggered, increasing the modulus and matching the expansion stress of the silicon-based active material; and / or, The second time is 12-18 minutes. Within this range, the fluorinated composite adhesive can be fully crystallized; and / or, The humidity at the second temperature is less than 5%. Humidity within this range at the second temperature can reduce moisture interference during the crystallization process; and / or, The third temperature is 105~115℃. Within this range, the elastic crosslinking of the fluoropolymer can be promoted, resulting in a crosslinking degree >70%; and / or, The third time is 8-12 minutes. Within this range, the fluoropolymer can undergo sufficient elastic cross-linking; and / or, The humidity at the third temperature is less than 1%, and within this range, the crosslinking reaction can be completed; and / or, The coating rate is 1~3 m / min. Within this range, the areal density can be controlled at 12±0.5 mg / cm³. 2 .

[0019] In some embodiments, the formation of a transport layer and a gas adsorption layer sequentially on the surface of the negative electrode active material layer to obtain the negative electrode sheet includes: An ion transport layer, an electron conduction layer, and a gas adsorption layer are sequentially formed on the surface of the negative electrode active material layer to obtain a negative electrode sheet. Among them, the methods for forming the ion transport layer include magnetron sputtering, which can improve the density of the ion transport layer and reduce cracks; Methods for forming an electron conduction layer include CVD growth, which can control the vertical orientation of the conductive agent and improve electron conduction capability. Methods for forming a gas adsorption layer include coating. Coating can maintain a certain gas adsorption layer thickness and enhance the gas adsorption capacity.

[0020] In some embodiments, when the ion transport layer is formed by magnetron sputtering: The power of magnetron sputtering is 150~200W; and / or, The gas flow rate for magnetron sputtering is 40–60 sccm; and / or, The substrate temperature for magnetron sputtering is 120~180℃; and / or, The magnetron sputtering rate is 0.2~0.8 nm / s.

[0021] Under these magnetron sputtering process parameters, an ion transport layer with a thickness of 20~40nm can be obtained.

[0022] In some embodiments, when the electron conduction layer is formed by CVD growth: The temperature for CVD is 400~600℃; and / or, The flux density of the electron conduction layer precursor material is 5~15 sccm; and / or, The C2H2 flow rate is 2~8 sccm; and / or, The pressure of C2H2 is 20~80 Pa; and / or, The growth time for CVD is 10-30 minutes.

[0023] Under these CVD process parameters, the vertical orientation of the conductive agent can be greater than 90%, resulting in an electron-conducting layer with a thickness of 150~250nm. Before depositing the conductive agent, a 1~10nm thick Ti seed layer can be pre-deposited on the surface of the ion transport layer to induce the vertical growth of carbide nanowires.

[0024] The slurry for the gas adsorption layer can be made by impregnating the surface of the electron conduction layer with an amino polymer concentration of 1~2 mg / mL, pH=8.5, oscillation speed of 200 rpm, reaction time of 2 h, and doping with 5%~10% porous oxide nanoparticles.

[0025] Fifthly, this application provides a solid-state battery, including a negative electrode sheet as described in the third aspect, or a negative electrode sheet prepared by the method described in the fourth aspect.

[0026] Fourthly, this application provides an electrical device including the solid-state battery described in the third aspect. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0028] In the development of next-generation high-energy-density solid-state batteries, silicon-based anodes are considered key materials for overcoming the bottlenecks of existing graphite anodes due to their ultra-high theoretical specific capacity (>1000 mAh / g). However, silicon-based materials face severe volume expansion (>300%) during charge and discharge, leading to problems such as electrode structure pulverization, intensified interfacial side reactions, and increased gas production. This, in turn, causes industrialization challenges such as short battery cycle life (<1000 cycles), low energy efficiency (<97%), and high internal resistance (>3 mΩ).

[0029] Conventionally, polyacrylic acid (PAA) binder and carbon coating (SiOx / C) are used to suppress the volume expansion of silicon-based anodes, combined with LiTFSI lithium salt to reduce interfacial impedance. However, the PAA binder has a low Young's modulus (0.5 GPa), which cannot match the cyclic expansion stress (8~12 MPa) of the SiOx / C silicon-based anode, resulting in an electrode crack density of 20 cracks / mm² and an expansion rate >15%; the interface is unstable, and the difference in thermal expansion coefficients between the carbon coating and the silicon-based material (CTE 4.5 × 10⁻⁶) is significant. -6 / K vs 2.3×10 -6 / K), after cycling, the interface cracks and the internal resistance increases by >20%; gas generation problem, the electrolyte (lithium hexafluorophosphate LiPF6 + lithium bisfluorosulfonyl imide LiFSI + DTD) decomposes and generates gas (CO2 >0.5mL / Ah).

[0030] Conventionally, lithium difluorophosphate (LiPO2F2) is added as a film-forming agent, combined with an in-situ curing process to improve electrolyte density. However, there are problems such as poor compatibility, with lithium difluorophosphate (LiPO2F2) reacting with SiOx / C to form an unstable SEI film (impedance fluctuation >20%); stress concentration, with localized stress concentration and expansion rate >10% during the lithium intercalation process of silicon-based anodes; and lack of gas generation suppression, with severe gas generation in the DTD + ethylene carbonate EC system.

[0031] In view of this, this application provides a silicon-based anode material and its preparation method, an anode sheet and its preparation method, a solid-state battery and an electrical device, so as to reduce the expansion of silicon-based batteries and improve the lifespan of silicon-based batteries.

[0032] In a first aspect, this application provides a silicon-based anode material, comprising a silicon-based active material, a fluorinated composite binder, and a conductive agent, wherein: The fluorinated composite adhesive includes fluorinated copolymers and fluorinated polymers; The fluorine content of the fluorinated copolymer is greater than or equal to 60%; The elastic modulus of the fluoropolymer is 0.8~1.0 GPa.

[0033] This application utilizes a fluorine-containing copolymer with a fluorine content greater than or equal to 60%, which can provide a large number of highly polar fluorine segments. These highly polar fluorine segments react with the F in lithium fluoride salts.- The van der Waals forces and dipole interactions (bond energy ≈ 20~50 kJ / mol) form a dense interfacial layer (contact angle 125°, tested with 1M LiPF6 / EC:DMC electrolyte), which can inhibit electrolyte penetration and improve interfacial stability and cycle life. The fluoropolymer has an elastic modulus of 0.8~1.0 GPa, providing elastic buffering for silicon-based anode materials. The three-dimensional elastic cross-linked network formed within it can uniformly disperse the expansion stress of the silicon-based anode, reducing crack formation, minimizing transport channel breakage, maintaining transport channel stability, and improving ion transport performance.

[0034] In conjunction with the first aspect, in some embodiments provided in this application, the fluorinated copolymer includes a first fluorinated compound and a second fluorinated compound, wherein the mass ratio of the first fluorinated compound and the second fluorinated compound is (6~7):(3~4). When the mass ratio of the first fluorinated compound and the second fluorinated compound is within this range, the modulus of the fluorinated copolymer is 1.0~1.2 GPa, which matches the expansion stress (8~12 MPa) of the silicon-based active material, thereby reducing the expansion stress of the silicon-based material to 3~5 MPa and thus reducing the expansion of the silicon-based material.

[0035] In conjunction with the first aspect, in some embodiments provided in this application, the fluorinated copolymer includes a first fluorinated material and a second fluorinated material, wherein: the first fluorinated material includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and perfluoroether, and selecting the above-mentioned first fluorinated material can copolymerize with the second fluorinated material to form a high-strength binder, thereby increasing the modulus of the fluorinated copolymer.

[0036] In conjunction with the first aspect, in some embodiments provided in this application, the fluorinated copolymer includes a first fluorinated compound and a second fluorinated compound, wherein: the second fluorinated compound includes at least one of HFP-VDF copolymer, TFE-P copolymer and hexafluoropropylene, and the selection of the above-mentioned second fluorinated compound can copolymerize with the first fluorinated compound to form a high-strength binder, thereby increasing the modulus of the fluorinated copolymer.

[0037] In conjunction with the first aspect, in some embodiments provided in this application, the fluorinated copolymer includes a first fluorinated compound and a second fluorinated compound, wherein the fluorinated polymer includes at least one of fluorinated polyurethane (FPU) and fluorinated elastomer (FE). The aforementioned fluorinated polymer contains elastic crosslinking groups, which can achieve dynamic stress buffering, and its degree of crosslinking is >70%, elongation at break is >300%, and modulus is 0.8~1.0 GPa. It can synergistically adapt to the expansion stress of the silicon anode with the fluorinated copolymer, reducing the expansion of the silicon-based material.

[0038] In conjunction with the first aspect, in some embodiments provided in this application, the mass ratio of the fluorinated copolymer to the fluorinated polymer is (5~6):(4~5). Within this range, the mass ratio of the fluorinated copolymer to the fluorinated polymer can better synergistically adapt to the expansion stress of the silicon anode and reduce the expansion of the silicon-based material.

[0039] In conjunction with the first aspect, in some embodiments provided in this application, the fluorinated composite binder accounts for 2% to 6% of the mass of the silicon-based anode material. This mass percentage of the fluorinated composite binder in the silicon-based anode material within this range can reduce the crowding of the anode active material, reduce energy density loss, and simultaneously reduce the expansion of the silicon-based active material.

[0040] It should be noted that the silicon-based active material includes, but is not limited to, at least one of SiOx / C composite materials. The conductive agent includes, but is not limited to, at least one of carbon nanotubes and graphene. The mass ratio of the silicon-based active material, the fluorinated composite binder, and the conductive agent is (88~95):(2~6):(2~6).

[0041] Secondly, this application provides a method for preparing a silicon-based anode material, which includes the following steps: Fluorinated copolymers and fluoropolymers are mixed with solvents to obtain fluorinated composite adhesive slurry; Silicon-based active material, conductive agent and fluorine-containing composite binder slurry are mixed and solvent is removed to obtain silicon-based anode material.

[0042] First, the fluorinated copolymer and fluorinated polymer are mixed with a solvent to obtain a fluorinated composite adhesive slurry. This allows the fluorinated copolymer and fluorinated polymer to copolymerize in the solvent to form a high-strength adhesive, thereby improving the modulus, interfacial bonding energy, and stress relaxation rate of the fluorinated composite adhesive and adapting it to the expansion stress of the silicon anode.

[0043] In conjunction with the second aspect, in some embodiments provided in this application, the stirring rate for mixing the fluorinated copolymer and the fluorinated polymer with the solvent is 1000~3000 rpm. Within this range, the stirring rate allows the fluorinated copolymer and the fluorinated polymer to rapidly copolymerize in the solvent to form a high-strength binder.

[0044] In conjunction with the second aspect, in some embodiments provided in this application, the temperature at which the fluorinated copolymer and the fluorinated polymer are mixed with the solvent is 40~60°C. The mixing temperature of the fluorinated copolymer and the fluorinated polymer with the solvent is within this range, which is conducive to the rapid copolymerization of the fluorinated copolymer and the fluorinated polymer in the solvent to form a high-strength binder.

[0045] In combination of these two aspects, in some embodiments provided in this application, the temperature at which the silicon-based active material, conductive agent and fluorinated composite binder slurry are mixed is 40~60°C. The mixing temperature of the silicon-based active material, conductive agent and fluorinated composite binder slurry within this range is conducive to the uniform dispersion of the fluorinated composite binder in the slurry.

[0046] In conjunction with the second aspect, in some embodiments provided in this application, the mixing time of the silicon-based active material, conductive agent, and fluorinated composite binder slurry is 30-60 minutes. Within this mixing time range, the fluorinated composite binder can be uniformly dispersed in the slurry, and the slurry viscosity can be stabilized at 5000±500 mPa·s (25℃).

[0047] Thirdly, this application provides a negative electrode sheet, comprising: Negative electrode current collector; A negative electrode active material layer; disposed on at least one side of the negative electrode current collector; and An interface modification layer is disposed on the surface of the negative electrode active material layer on the side opposite to the negative electrode current collector; The material of the negative electrode active material layer includes the silicon-based negative electrode material described in the first aspect; The interface modification layer includes a transport layer and a gas adsorption layer, wherein the transport layer is disposed between the gas adsorption layer and the negative electrode active material layer.

[0048] The negative electrode active material layer comprises the silicon-based negative electrode material described in the first aspect, which can reduce the expansion of the silicon-based negative electrode material. Simultaneously, on the surface of the negative electrode active material layer facing away from the negative electrode current collector, there are an interface modification layer, a transport layer, and a gas adsorption layer. The transport layer can improve ion transport and electron conduction capabilities, while the adsorption layer can adsorb gas generated during the use of the silicon-based battery, reducing battery expansion and improving the overall performance of the silicon-based battery. The fluorinated composite binder in the silicon-based negative electrode material solves the mechanical mismatch problem of traditional silicon-based negative electrode active materials, and the interface modification layer solves the ion / electron transport and gas generation problems. The two work synergistically to achieve a triple optimization of "mechanical-electrochemical-gas generation".

[0049] In conjunction with the third aspect, in some embodiments provided in this application, the transport layer includes an ion transport layer and an electron conduction layer, wherein the ion transport layer is disposed between the electron conduction layer and the negative electrode active material layer; the material of the ion transport layer includes at least one of lithium aluminum fluoride (LiAlF4) and lithium fluoride (LiF), and the material of the ion transport layer is capable of providing a lithium ion transport number t ＋ ≥0.8, thereby improving ion transport performance, and its chemical stability, decomposition voltage >4.5V, is beneficial to improving the stability of silicon-based batteries, and can also suppress the dissolution of transition metals.

[0050] In conjunction with the third aspect, in some embodiments provided in this application, the material of the electron conduction layer includes at least one of carbon nanotubes, silicon carbide nanowires, and titanium carbide nanowires. The above-mentioned electron conduction layer material can reduce electronic impedance and improve electron transport efficiency. Among them, carbon nanotubes are stable in LiPF6 and have few side reactions.

[0051] In conjunction with the third aspect, in some embodiments provided in this application, the thickness of the ion transport layer is 20~40nm. The thickness of the ion transport layer within this range can improve the ion transport performance while reducing the crowding of the negative electrode active material layer and reducing energy density loss.

[0052] In conjunction with the third aspect, in some embodiments provided in this application, the thickness of the electron conduction layer is 150~250nm. Within this range, the thickness of the electron conduction layer can improve electron transport performance while reducing the crowding out of the negative electrode active material layer and reducing energy density loss.

[0053] In conjunction with the third aspect, in some embodiments provided in this application, the material of the gas adsorption layer includes porous oxides and amino-containing polymers. The porous oxides and amino-containing polymers have no side reactions with the positive electrode, are stable in performance, and have a strong CO2 adsorption capacity. The amino-containing polymer includes at least one of polydopamine and polyaniline. The amino-containing polymer can adsorb CO2, SO2, and HF.

[0054] In conjunction with the third aspect, in some embodiments provided in this application, the material of the gas adsorption layer includes porous oxides and amino-containing polymers. The porous oxides and amino-containing polymers have no side reactions with the positive electrode, are stable in performance, and have a strong CO2 adsorption capacity. The porous oxides include at least one of nano-Al2O3 and nano-SiO2. The porous oxides can adsorb HF and neutralize acidic byproducts.

[0055] In conjunction with the third aspect, in some embodiments provided in this application, the material of the gas adsorption layer includes porous oxides and amino-containing polymers. The porous oxides and amino-containing polymers have no side reactions with the positive electrode, are stable in performance, and have a strong CO2 adsorption capacity. The mass ratio of the amino-containing polymer to the porous oxide is (9~19):1. Within this range, the mass ratio of the amino-containing polymer to the porous oxide can balance the chemical adsorption and physical adsorption capacities, resulting in a CO2 adsorption rate ≥90% and an HF adsorption rate ≥80%.

[0056] In conjunction with the third aspect, in some embodiments provided in this application, the material of the gas adsorption layer includes porous oxides and amino-containing polymers. The porous oxides and amino-containing polymers have no side reactions with the positive electrode, have stable performance, and have a strong CO2 adsorption capacity. The thickness of the gas adsorption layer is 10~30nm. The thickness of the gas adsorption layer within this range can reduce the crowding of the negative electrode active material layer and reduce energy density loss while adsorbing and generating gas.

[0057] In conjunction with the third aspect, in some embodiments provided in this application, the material of the gas adsorption layer includes porous oxides and amino-containing polymers. The porous oxides and amino-containing polymers do not undergo side reactions with the positive electrode, exhibit stable performance, and have a strong CO2 adsorption capacity. Specifically, the porosity of the gas adsorption layer is 30% to 50%. This porosity range enhances the adsorption capacity for CO2 and HF gases, reduces gas production, and minimizes battery expansion.

[0058] Fourthly, this application provides a method for preparing a negative electrode sheet, which includes the following steps: Fluorinated copolymers and fluoropolymers are mixed with solvents to obtain fluorinated composite adhesive slurry; A silicon-based active material, a conductive agent, and a fluorine-containing composite binder slurry are mixed to obtain a silicon-based anode material slurry. A silicon-based negative electrode material slurry is coated on at least one side of the negative electrode current collector and dried to obtain an electrode assembly containing a negative electrode active material layer. A transport layer and a gas adsorption layer are sequentially formed on the surface of the negative electrode active material layer to obtain the negative electrode sheet.

[0059] The negative electrode active material layer comprises the silicon-based negative electrode material described in the first aspect, which can reduce the expansion of the silicon-based negative electrode material. Simultaneously, on the surface of the negative electrode active material layer facing away from the negative electrode current collector, there are an interface modification layer, a transport layer, and a gas adsorption layer. The transport layer can improve ion transport and electron conduction capabilities, while the adsorption layer can adsorb gas generated during the use of the silicon-based battery, reducing battery expansion and improving the overall performance of the silicon-based battery. The fluorinated composite binder in the silicon-based negative electrode material solves the mechanical mismatch problem of traditional silicon-based negative electrode active materials, and the interface modification layer solves the ion / electron transport and gas generation problems. The two work synergistically to achieve a triple optimization of "mechanical-electrochemical-gas generation".

[0060] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein: the first temperature is 75~85°C, and the first temperature is within this range, which can gently remove the solvent and reduce the generation of microcracks.

[0061] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein: the first time is 8 to 12 minutes, and the first time is within this range, which can sufficiently remove the solvent.

[0062] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein: the humidity at the first temperature is less than 10%, and the humidity at the first temperature is within this range, which can reduce the microcracks caused by solvent residue.

[0063] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein: the second temperature is 95~105°C, and the second temperature within this range can trigger the crystallization of the fluorinated composite binder, increase the modulus, and match the expansion stress of the silicon-based active material.

[0064] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein the second time is 12 to 18 minutes. Within this range, the fluorine-containing composite binder can be fully crystallized.

[0065] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein the humidity at the second temperature is less than 5%, and the humidity at the second temperature is within this range, which can reduce water vapor interference in the crystallization process.

[0066] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein the third temperature is 105~115°C. Within this range, the third temperature can promote the elastic crosslinking of the fluoropolymer, resulting in a crosslinking degree >70%.

[0067] In conjunction with the fourth aspect, in some embodiments provided in this application, in the process of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer, the drying step sequentially includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein: the third time is 8 to 12 minutes, and the third time is within this range, which allows the fluoropolymer to be fully elastically crosslinked.

[0068] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein the humidity at the third temperature is less than 1%, and the humidity at the third temperature is within this range, which can make the crosslinking reaction complete.

[0069] In conjunction with the fourth aspect, in some embodiments provided in this application, the step of coating at least one side of the negative electrode current collector with a silicon-based negative electrode material slurry and drying it to obtain an electrode assembly containing a negative electrode active material layer includes, in sequence, drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein the coating rate is 1~3 m / min. A coating rate within this range can achieve an areal density of 12±0.5 mg / cm³. 2 .

[0070] In conjunction with the fourth aspect, in some embodiments provided in this application, the formation of a transport layer and a gas adsorption layer sequentially on the surface of the negative electrode active material layer to obtain the negative electrode sheet includes: An ion transport layer, an electron conduction layer, and a gas adsorption layer are sequentially formed on the surface of the negative electrode active material layer to obtain a negative electrode sheet. Among them, the methods for forming the ion transport layer include magnetron sputtering, which can improve the density of the ion transport layer and reduce cracks; Methods for forming an electron conduction layer include CVD growth, which can control the vertical orientation of the conductive agent and improve electron conduction capability. Methods for forming a gas adsorption layer include coating. Coating can maintain a certain gas adsorption layer thickness and enhance the gas adsorption capacity.

[0071] In conjunction with the fourth aspect, in some embodiments provided in this application, when forming an ion transport layer by magnetron sputtering: the magnetron sputtering power is 150~200W; the magnetron sputtering gas flow rate is 40~60sccm; the magnetron sputtering substrate temperature is 120~180℃; and the magnetron sputtering rate is 0.2~0.8nm / s. Under these magnetron sputtering process parameters, an ion transport layer with a thickness of 20~40nm can be obtained.

[0072] In conjunction with the fourth aspect, in some embodiments provided in this application, when forming the electron conduction layer by CVD growth: the CVD temperature is 400~600℃; the flow rate of the electron conduction layer precursor material is 5~15 sccm; the C2H2 flow rate is 2~8 sccm; the C2H2 pressure is 20~80 Pa; and the CVD growth time is 10~30 min. Under these CVD process parameters, the vertical orientation of the conductive agent can be greater than 90%, resulting in an electron conduction layer with a thickness of 150~250 nm. Before depositing the conductive agent, a 1~10 nm thick Ti seed layer can be pre-deposited on the surface of the ion transport layer to induce the vertical growth of carbide nanowires.

[0073] The slurry for the gas adsorption layer can be a porous oxide nanoparticle with an amino polymer concentration of 1~2 mg / mL, pH=8.5, doped with 5%~10%, oscillated at 200 rpm, reacted for 2 hours, and then impregnated on the surface of the electron conduction layer.

[0074] Fifthly, this application provides a solid-state battery, including a negative electrode sheet as described in the third aspect, or a negative electrode sheet prepared by the method described in the fourth aspect.

[0075] Fourthly, this application provides an electrical device, including the solid-state battery described in the third aspect. The electrical device includes, but is not limited to, new energy vehicles, energy storage devices, and portable electronic devices.

[0076] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0077] Example 1 Embodiment 1 of this application provides a silicon-based anode material and its preparation method, including the following steps: 1) Raw materials for silicon-based anode materials: Silicon-based active material: SiOx / C composite material (carbon-coated silicon suboxide anode material, specific capacity ≥700mAh / g); Fluorinated composite adhesive: fluorinated copolymer (polyvinylidene fluoride, HFP-VDF copolymer, mass ratio 7:3) and fluorinated polymer (fluorinated polyurethane), with a mass ratio of fluorinated copolymer to fluorinated polymer of 6:4; Conductive agent: Carbon nanotubes, conductivity > 10 4 S / cm; The mass ratio of silicon-based active material, fluorine-containing composite binder, and conductive agent is 90:5:5; Solvent: NMP.

[0078] 2) Preparation method: Fluorinated copolymers and fluorinated polymers were dissolved in NMP solvent, and the mixture was stirred at 2000 rpm and 50°C to obtain a fluorinated composite adhesive solution.

[0079] A fluorine-containing composite binder solution was mixed with SiOx / C and conductive carbon nanotubes for 45 minutes until the viscosity reached 5000 mPa·s, resulting in a silicon-based anode active material slurry.

[0080] Example 2 Embodiment 2 of this application provides a silicon-based anode material and its preparation method, including the following steps: 1) Raw materials for silicon-based anode materials: Silicon-based active material: SiOx / C composite material (carbon-coated silicon suboxide anode material, specific capacity ≥700mAh / g); Fluorinated composite adhesive: fluorinated copolymer (polytetrafluoroethylene, TFE-P copolymer, mass ratio 6:4) and fluorinated polymer (fluorinated elastomer), with a mass ratio of fluorinated copolymer to fluorinated polymer of 5:5; Conductive agent: Carbon nanotubes, conductivity > 10 4 S / cm; The mass ratio of silicon-based active material, fluorine-containing composite binder, and conductive agent is 88:6:6; Solvent: NMP.

[0081] 2) Preparation method: Fluorinated copolymers and fluorinated polymers were dissolved in NMP solvent, and the mixture was stirred at 3000 rpm and 40°C to obtain a fluorinated composite adhesive solution.

[0082] A fluorine-containing composite binder solution was mixed with SiOx / C and conductive carbon nanotubes for 60 minutes until the viscosity reached 5000 mPa·s, resulting in a silicon-based anode active material slurry.

[0083] Example 3 Embodiment 3 of this application provides a silicon-based anode material and its preparation method, including the following steps: 1) Raw materials for silicon-based anode materials: Silicon-based active material: SiOx / C composite material (carbon-coated silicon suboxide anode material, specific capacity ≥700mAh / g); Fluorinated composite adhesive: fluorinated copolymer (perfluoroether, hexafluoropropylene, mass ratio 13:7) and fluorinated polymer (fluorinated polyurethane), with a mass ratio of fluorinated copolymer to fluorinated polymer of 11:9; Conductive agent: Carbon nanotubes, conductivity > 10 4 S / cm; The mass ratio of silicon-based active material, fluorine-containing composite binder, and conductive agent is 95:3:2; Solvent: NMP (N-methylpyrrolidone).

[0084] 2) Preparation method: Fluorinated copolymers and fluorinated polymers were dissolved in NMP solvent, and the mixture was stirred at 1000 rpm and 60°C to obtain a fluorinated composite adhesive solution.

[0085] A fluorine-containing composite binder solution was mixed with SiOx / C and conductive carbon nanotubes for 30 minutes until the viscosity reached 5000 mPa·s, resulting in a silicon-based anode active material slurry.

[0086] Example 4 Example 4 of this application provides a silicon-based anode material and its preparation method, including the following steps: 1) Raw materials for silicon-based anode materials: Silicon-based active material: SiOx / C composite material (carbon-coated silicon suboxide anode material, specific capacity ≥700mAh / g); Fluorinated composite adhesive: fluorinated copolymer (polytetrafluoroethylene, HFP-VDF copolymer, mass ratio 1.8:1) and fluorinated polymer (fluorinated elastomer), with a mass ratio of fluorinated copolymer to fluorinated polymer of 1.2:1; Conductive agent: Carbon nanotubes, conductivity > 10 4 S / cm; The mass ratio of silicon-based active material, fluorine-containing composite binder, and conductive agent is 93:2:5; Solvent: NMP (N-methylpyrrolidone).

[0087] 2) Preparation method: Fluorinated copolymers and fluorinated polymers were dissolved in NMP solvent, and the mixture was stirred at 2000 rpm and 50°C to obtain a fluorinated composite adhesive solution.

[0088] A fluorine-containing composite binder solution was mixed with SiOx / C and conductive carbon nanotubes until the viscosity reached 5000 mPa·s to obtain a silicon-based anode active material slurry.

[0089] Example 5 Embodiment 5 of this application provides a silicon-based anode material and its preparation method, including the following steps: 1) Raw materials for silicon-based anode materials: Silicon-based active material: SiOx / C composite material (carbon-coated silicon suboxide anode material, specific capacity ≥700mAh / g); Fluorinated composite adhesive: fluorinated copolymer (polyvinylidene fluoride, HFP-VDF copolymer, mass ratio 2:1) and fluorinated polymer (fluorinated polyurethane), with a mass ratio of fluorinated copolymer to fluorinated polymer of 1.3:1; Conductive agent: Carbon nanotubes, conductivity > 10 4 S / cm; The mass ratio of silicon-based active material, fluorine-containing composite binder, and conductive agent is 91:5:4; Solvent: NMP (N-methylpyrrolidone).

[0090] 2) Preparation method: Fluorinated copolymers and fluorinated polymers were dissolved in NMP solvent, and the mixture was stirred at 2000 rpm and 50°C to obtain a fluorinated composite adhesive solution.

[0091] A fluorine-containing composite binder solution was mixed with SiOx / C and conductive carbon nanotubes until the viscosity reached 5000 mPa·s to obtain a silicon-based anode active material slurry.

[0092] Example 6 Example 6 of this application provides a negative electrode sheet and its preparation method, which uses the silicon-based negative electrode active material slurry as in Example 1, and includes the following steps: A negative electrode active material slurry was coated on both sides of the negative electrode current collector at a coating speed of 2 m / min and an areal density of 12 mg / cm³. 2 ; Intermittent drying: 80℃, 10min, humidity <10% — 100℃, 15min, humidity <5% — 110℃, 10min, humidity <1%, to obtain the negative electrode active material layer; Using lithium fluoroaluminate (LiAlF4) as raw material, an ion transport layer with a thickness of 30 nm was sputtered on the surface of the negative electrode active material layer at a power of 180W, an Ar gas flow rate of 50 sccm, a substrate temperature of 150℃, and a sputtering rate of 0.5 nm / s. A 5 nm thick Ti seed layer was pre-deposited on the surface of the electron transport layer. The carbon nanotube electron transport layer was formed by CVD at a temperature of 500 °C, using TiCl4+C2H2 as the precursor, a pressure of 50 Pa, and a growth time of 20 min. The CNTs were arranged in a vertical orientation with an orientation rate of >90%. A polydopamine-Al2O3 porous adsorption layer was formed by impregnating the surface of the electron transport layer. The polydopamine concentration was 1.5 mg / mL, the solvent was Tris-HCl buffer, pH=8.5, Al2O3 nanoparticles were added, and the reaction time was 2 h to obtain the coating solution. The mass percentage of Al2O3 in the porous adsorption layer was 5%, and the thickness of the porous adsorption layer was 20 nm.

[0093] Example 7 Example 7 of this application provides a negative electrode sheet and its preparation method, which uses the silicon-based negative electrode active material slurry as in Example 2, and includes the following steps: A negative electrode active material slurry was coated on both sides of the negative electrode current collector at a coating speed of 1 m / min and an areal density of 12 mg / cm³. 2 ; Intermittent drying: 75℃, 12min, humidity <10% - 95℃, 18min, humidity <5% - 105℃, 12min, humidity <1%, to obtain the negative electrode active material layer; Using lithium fluoride as raw material, an ion transport layer with a thickness of 20 nm was sputtered on the surface of the negative electrode active material layer at a power of 150W, an Ar gas flow rate of 60 sccm, a substrate temperature of 180℃, and a sputtering rate of 0.2 nm / s. A 5 nm thick Ti seed layer was pre-deposited on the surface of the electron transport layer. The carbon nanotube electron transport layer was formed by CVD at a temperature of 400 °C, using TiCl4+C2H2 as the precursor, a pressure of 20 Pa, and a growth time of 30 min. The CNTs were arranged in a vertical orientation with an orientation rate of >90%. A polyaniline-Al2O3 porous adsorption layer was formed by impregnating the surface of the electron transport layer. The polyaniline concentration was 1.5 mg / mL, the solvent was Tris-HCl buffer, pH=8.5, Al2O3 nanoparticles were added, and the reaction time was 1 h to obtain the coating solution. The mass ratio of Al2O3 in the porous adsorption layer was 10%, and the thickness of the porous adsorption layer was 10 nm.

[0094] Example 8 Example 8 of this application provides a negative electrode sheet and its preparation method, which uses the silicon-based negative electrode active material slurry as in Example 3, and includes the following steps: A negative electrode active material slurry was coated on both sides of the negative electrode current collector at a coating speed of 3 m / min and a surface density of 12 mg / cm2. Intermittent drying: 85℃, 8min, humidity <10% - 105℃, 12min, humidity <5% - 115℃, 8min, humidity <1%, to obtain the negative electrode active material layer; Using lithium fluoroaluminate (LiAlF4) as the raw material, an ion transport layer with a thickness of 40 nm was sputtered on the surface of the negative electrode active material layer at a power of 200W, an Ar gas flow rate of 40 sccm, a substrate temperature of 120℃, and a sputtering rate of 0.8 nm / s. A 5 nm thick Ti seed layer was pre-deposited on the surface of the electron transport layer. The carbon nanotube electron transport layer was formed by CVD at a temperature of 600 °C, using TiCl4+C2H2 as the precursor, a pressure of 80 Pa, and a growth time of 10 min. The CNTs were arranged in a vertical orientation with an orientation rate of >90%. A polydopamine-Al2O3 porous adsorption layer was formed by impregnating the surface of the electron transport layer. The polydopamine concentration was 1.5 mg / mL, the solvent was Tris-HCl buffer, pH=8.5, Al2O3 nanoparticles were added, and the reaction time was 3 h to obtain the coating solution. The mass percentage of Al2O3 in the porous adsorption layer was 7%, and the thickness of the porous adsorption layer was 20 nm.

[0095] Example 9 Example 9 of this application provides a negative electrode sheet and its preparation method, which uses the silicon-based negative electrode active material slurry as in Example 4, and includes the following steps: A negative electrode active material slurry was coated on both sides of the negative electrode current collector at a coating speed of 1.5 m / min and an areal density of 12 mg / cm2. Intermittent drying: 83℃, 10min, humidity <10% — 102℃, 15min, humidity <5% — 114℃, 10min, humidity <1%, to obtain the negative electrode active material layer; Using lithium fluoride as raw material, an ion transport layer with a thickness of 30 nm was sputtered on the surface of the negative electrode active material layer at a power of 180W, an Ar gas flow rate of 50 sccm, a substrate temperature of 150℃, and a sputtering rate of 0.5 nm / s. A 5 nm thick Ti seed layer was pre-deposited on the surface of the electron transport layer. The carbon nanotube electron transport layer was formed by CVD at a temperature of 500 °C, using TiCl4+C2H2 as the precursor, a pressure of 50 Pa, and a growth time of 20 min. The CNTs were arranged in a vertical orientation with an orientation rate of >90%. A polyaniline-Al2O3 porous adsorption layer was formed by impregnating the surface of the electron transport layer. The polyaniline concentration was 1.5 mg / mL, the solvent was Tris-HCl buffer, pH=8.5, Al2O3 nanoparticles were added, and the reaction time was 2 h to obtain the coating solution. The mass percentage of Al2O3 in the porous adsorption layer was 8%, and the thickness of the porous adsorption layer was 35 nm.

[0096] Example 10 Example 10 of this application provides a negative electrode sheet and its preparation method, which uses the silicon-based negative electrode active material slurry as in Example 5, and includes the following steps: A negative electrode active material slurry was coated on both sides of the negative electrode current collector at a coating speed of 2.5 m / min and an areal density of 12 mg / cm2. Intermittent drying: 78℃, 10min, humidity <10% - 99℃, 15min, humidity <5% - 114℃, 10min, humidity <1%, to obtain the negative electrode active material layer; Using lithium fluoroaluminate (LiAlF4) as raw material, an ion transport layer with a thickness of 30 nm was sputtered on the surface of the negative electrode active material layer at a power of 180W, an Ar gas flow rate of 50 sccm, a substrate temperature of 150℃, and a sputtering rate of 0.5 nm / s. A 5 nm thick Ti seed layer was pre-deposited on the surface of the electron transport layer. The carbon nanotube electron transport layer was formed by CVD at a temperature of 500 °C, using TiCl4+C2H2 as the precursor, a pressure of 50 Pa, and a growth time of 20 min. The CNTs were arranged in a vertical orientation with an orientation rate of >90%. A polydopamine-Al2O3 porous adsorption layer was formed by impregnating the surface of the electron transport layer. The polydopamine concentration was 1.5 mg / mL, the solvent was Tris-HCl buffer, pH=8.5, Al2O3 nanoparticles were added, and the reaction time was 2 h to obtain the coating solution. The mass percentage of Al2O3 in the porous adsorption layer was 9%, and the thickness of the porous adsorption layer was 25 nm.

[0097] Comparative Example 1 Comparative Example 1 of this application provides a silicon-based anode material and its preparation method, which is similar to Example 3, except that the binder is replaced with polyacrylic acid (PAA).

[0098] Comparative Example 2 Comparative Example 2 of this application provides a silicon-based anode material and its preparation method, which is similar to Example 3, except that it does not contain fluorine-containing copolymers.

[0099] Comparative Example 3 Comparative Example 3 of this application provides a silicon-based anode material and its preparation method, which is similar to Example 3, except that it does not contain fluorinated polymers.

[0100] Comparative Example 4 Comparative Example 4 of this application provides a negative electrode sheet, which is similar to Example 8, except that it uses the negative electrode active material of Comparative Example 1.

[0101] Comparative Example 5 Comparative Example 5 of this application provides a negative electrode sheet, which is similar to Example 8, except that it uses the negative electrode active material of Comparative Example 2.

[0102] Comparative Example 6 Comparative Example 6 of this application provides a negative electrode sheet, which is similar to Example 8, except that it uses the negative electrode active material of Comparative Example 3.

[0103] Comparative Example 7 Comparative Example 7 of this application provides a negative electrode sheet, which is similar to Example 8, except that it uses the negative electrode active material of Comparative Example 1 and does not contain an interface modification layer.

[0104] Comparative Example 8 Comparative Example 8 of this application provides a negative electrode sheet, which is similar to Example 8, except that it uses the negative electrode active material of Comparative Example 1 and does not contain a gas adsorption layer.

[0105] Comparative Example 9 Comparative Example 9 of this application provides a negative electrode sheet, which is similar to Example 8, except that it uses the negative electrode active material of Comparative Example 1 and does not contain a transport layer.

[0106] Comparative Example 10 Comparative Example 10 of this application provides a negative electrode sheet, which is similar to Example 8, except that it uses the negative electrode active material of Comparative Example 1 and does not contain an ion transport layer.

[0107] Performance testing The silicon-based anode sheets from Examples 6 to 10 and Comparative Examples 4 to 10 were assembled into solid-state batteries, and their electrical performance was tested, including their expansion rate, DC internal resistance (DCR), gas production, and cycle performance. The specific steps are as follows: Assembly process: Positive electrode: NCM9 (lithium nickel cobalt manganese oxide, 90% nickel content) is the positive electrode; Separator: Boehmite-coated PE membrane; Electrolyte: Oxide / polymer composite solid electrolyte (LLZO lithium lanthanum zirconium oxide ceramic particles + PEO polyethylene oxide polymer + 10wt% dual-salt liquid electrolyte (LiPF6:LiFSI=1:1)); Assembly: Stacking process, packaged into soft-pack cells.

[0108] Performance testing methods and steps: Expansion rate: The rate of change in battery thickness from the initial state (0% SOC) to the final state (100% SOC) is measured under constant pressure and temperature (typically 25±1℃).

[0109] DC internal resistance (DCR): 1) Charge the cell to 4.2V with constant current and constant voltage at 1 / 3C, cut off current at 0.05C, let stand for 0.5h, discharge the cell to 2.5V with constant current at 1 / 3C, let stand for 0.5h, repeat 3 times; 2) Charge to the specified SOC (50% SOC) with standard charging current, let stand for 60min, discharge the cell at 1.0C for 30s, let stand for 40s, charge the cell at 1.0C for 30s; increase the discharge DCR by 3C / 10s, let stand for 40s, charge at 1.25C / 10s; 3) DCR = (U_initial - U_end) / I (U_initial is the voltage before charging and discharging, U_end is the voltage at the end of charging and discharging).

[0110] Gas production: 1) Soft-pack battery fully charged to 4.2V, constant temperature 25℃±1℃; 2) In-situ gas chromatography (detection of CO2 / H2 release, unit mL / Ah).

[0111] Cyclic performance: 1) The cell undergoes 3 standard charge-discharge cycles, is left to stand until thermal equilibrium is reached, and the capacity of the last discharge is taken as C0; (25℃±1℃); 2) The cell undergoes a standard discharge after a DC internal resistance test; 3) At 25℃±1℃, the cell is charged in steps to 99% SOC, left to stand until thermal equilibrium is reached, discharged at 1C to 1% SOC, and left to stand until thermal equilibrium is reached; until the capacity decays to 80% SOH, the number of cycles is recorded.

[0112] The specific test results are shown in Table 1: Table 1 Performance of the negative electrode sheets of Examples 6 to 10 and Comparative Examples 4 to 10

[0113] As shown in Table 1, the negative electrode sheets from Examples 6 to 10, when assembled into batteries, exhibit the following performance advantages: The expansion rate was 8-9% (comparative examples were all >9.5%), the DCR internal resistance was 1.8-2.0 mΩ (comparative examples were all >2.1 mΩ), the gas production rate was 0.25-0.30 mL / Ah (comparative examples were all >0.38 mL / Ah), and the cycle life was 1100-1200 cycles (comparative examples were all <950 cycles).

[0114] Comparative Example 4, due to the use of PAA adhesive, suffers from high expansion defects caused by mechanical mismatch.

[0115] Comparative Example 5, lacking fluorinated copolymers, suffers from insufficient modulus and high expansion rate.

[0116] Comparative Example 6, lacking fluoropolymers, exhibits defects such as stress buffer failure and high expansion rate.

[0117] Comparative Example 7, lacking an interface modification layer, suffers from drawbacks such as blocked ion / electron transport, numerous side reactions, and excessive gas production.

[0118] Comparative Example 8 has the defect of high gas production because it does not have a gas adsorption layer.

[0119] Comparative Example 9 has the defect of increased interface impedance due to the absence of a transmission layer.

[0120] Comparative Example 10 has a defect that hinders lithium-ion migration because it does not have an ion transport layer.

[0121] In summary, by using fluorinated copolymers with a fluorine content greater than or equal to 60%, a large number of highly polar fluorine segments can be provided. These highly polar fluorine segments react with the F in lithium fluoride salts. - The van der Waals forces and dipole interactions (bond energy ≈ 20~50 kJ / mol) form a dense interfacial layer (contact angle 125°, tested with 1M LiPF6 / EC:DMC electrolyte), which can inhibit electrolyte penetration and improve interfacial stability and cycle performance. The fluoropolymer has an elastic modulus of 0.8~1.0 GPa, providing elastic buffering for silicon-based anode materials. The three-dimensional elastic cross-linked network formed within it can uniformly disperse the expansion stress of the silicon-based anode, reducing crack formation, minimizing transport channel breakage, maintaining transport channel stability, and improving ion transport performance.

[0122] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0123] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0124] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A silicon-based anode material, characterized in that, Includes silicon-based active materials, fluorinated composite binders, and conductive agents, among which: The fluorinated composite adhesive includes fluorinated copolymers and fluorinated polymers; The fluorine content of the fluorinated copolymer is greater than or equal to 60%; The elastic modulus of the fluoropolymer is 0.8~1.0 GPa.

2. The silicon-based anode material as described in claim 1, characterized in that, The fluorinated copolymer comprises a first fluorinated compound and a second fluorinated compound, wherein: The mass ratio of the first fluorinated compound to the second fluorinated compound is (6~7):(3~4); and / or, The first fluorinated material includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and perfluoroether; and / or, The second fluorinated compound includes at least one of HFP-VDF copolymer, TFE-P copolymer, and hexafluoropropylene; and / or, The fluoropolymer includes at least one of fluorinated polyurethane and fluorinated elastomer.

3. The silicon-based anode material as described in claim 1, characterized in that: The mass ratio of the fluorinated copolymer to the fluorinated polymer is (5~6):(4~5); and / or, The fluorinated composite binder accounts for 2% to 6% of the mass of the silicon-based anode material.

4. A method for preparing a silicon-based anode material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Fluorinated copolymers and fluoropolymers are mixed with solvents to obtain fluorinated composite adhesive slurry; Silicon-based active material, conductive agent and fluorine-containing composite binder slurry are mixed and solvent is removed to obtain silicon-based anode material.

5. The method for preparing the silicon-based anode material as described in claim 4, characterized in that: The stirring rate for mixing the fluorinated copolymer and the fluorinated polymer with the solvent is 1000~3000 rpm; and / or, The temperature at which the fluorinated copolymer and fluorinated polymer are mixed with the solvent is 40~60℃; and / or, The temperature for mixing the silicon-based active material, conductive agent, and fluorine-containing composite binder slurry is 40~60℃; and / or, The mixing time for silicon-based active materials, conductive agents and fluorine-containing composite adhesive slurry is 30-60 minutes.

6. A negative electrode sheet, characterized in that, include: Negative electrode current collector; Negative electrode active material layer; Located on at least one side of the negative electrode current collector; and An interface modification layer is disposed on the surface of the negative electrode active material layer on the side opposite to the negative electrode current collector; The material of the negative electrode active material layer includes the silicon-based negative electrode material as described in any one of claims 1 to 3; The interface modification layer includes a transport layer and a gas adsorption layer, wherein the transport layer is disposed between the gas adsorption layer and the negative electrode active material layer.

7. The negative electrode sheet as described in claim 6, characterized in that, The transport layer includes an ion transport layer and an electron conduction layer, wherein the ion transport layer is disposed between the electron conduction layer and the negative electrode active material layer. The ion transport layer is made of at least one of lithium aluminum fluoride and lithium fluoride; and / or, The electron conduction layer is made of at least one of carbon nanotubes, silicon carbide nanowires, and titanium carbide nanowires; and / or, The thickness of the ion transport layer is 20~40 nm; and / or, The thickness of the electron conduction layer is 150~250nm.

8. The negative electrode sheet as described in claim 6, characterized in that: The gas adsorption layer is made of porous oxides and amino-containing polymers, wherein: The amino-containing polymer includes at least one of polydopamine and polyaniline; and / or, The porous oxide includes at least one of nano-Al2O3 and nano-SiO2; and / or, The mass ratio of the amino-containing polymer to the porous oxide is (9~19):1; and / or, The thickness of the gas adsorption layer is 10~30 nm; and / or, The porosity of the gas adsorption layer is 30%~50%.

9. A method for preparing a negative electrode sheet as described in any one of claims 6 to 8, characterized in that, Includes the following steps: Fluorinated copolymers and fluoropolymers are mixed with solvents to obtain fluorinated composite adhesive slurry; A silicon-based active material, a conductive agent, and a fluorine-containing composite binder slurry are mixed to obtain a silicon-based anode material slurry. A silicon-based negative electrode material slurry is coated on at least one side of the negative electrode current collector and dried to obtain an electrode assembly containing a negative electrode active material layer. A transport layer and a gas adsorption layer are sequentially formed on the surface of the negative electrode active material layer to obtain the negative electrode sheet.

10. The method for preparing the negative electrode sheet as described in claim 9, characterized in that, In the electrode assembly in which a silicon-based negative electrode material slurry is coated on at least one side of the negative electrode current collector and dried to obtain a negative electrode active material layer, the drying step sequentially includes drying at a first temperature for a first time, drying at a second temperature for a second time, and drying at a third temperature for a third time, wherein: The first temperature is 75~85℃; and / or, The first time is 8-12 minutes; and / or, The humidity at the first temperature is less than 10%; and / or, The second temperature is 95~105℃; and / or, The second time is 12-18 minutes; and / or, The humidity at the second temperature is less than 5%; and / or, The third temperature is 105~115℃; and / or, The third time is 8-12 minutes; and / or, The humidity at the third temperature is less than 1%; and / or, The coating rate is 1~3 m / min.

11. The method for preparing the negative electrode sheet as described in claim 9, characterized in that, The negative electrode sheet is obtained by sequentially forming a transport layer and a gas adsorption layer on the surface of the negative electrode active material layer, wherein the transport layer and the gas adsorption layer are formed thereon. An ion transport layer, an electron conduction layer, and a gas adsorption layer are sequentially formed on the surface of the negative electrode active material layer to obtain a negative electrode sheet. Methods for forming ion transport layers include magnetron sputtering. Methods for forming an electron-conducting layer include CVD growth. Methods for forming a gas adsorption layer include impregnation.

12. The method for preparing the negative electrode sheet as described in claim 11, characterized in that, When forming an ion transport layer by magnetron sputtering: The power of magnetron sputtering is 150~200W; and / or, The gas flow rate for magnetron sputtering is 40–60 sccm; and / or, The substrate temperature for magnetron sputtering is 120~180℃; and / or, The magnetron sputtering rate is 0.2~0.8 nm / s.

13. The method for preparing the negative electrode sheet as described in claim 11, characterized in that, When forming an electron-conducting layer using CVD growth: The temperature for CVD is 400~600℃; and / or, The flux density of the electron conduction layer precursor material is 5~15 sccm; and / or, The C2H2 flow rate is 2~8 sccm; and / or, The pressure of C2H2 is 20~80 Pa; and / or, The growth time for CVD is 10-30 minutes.

14. The method for preparing the negative electrode sheet as described in claim 11, characterized in that, Methods for forming a gas adsorption layer by coating include: The porous oxide and the amino-containing polymer are mixed in a solvent to obtain a mixture; The mixture is coated on the surface of the electron conduction layer to obtain the gas adsorption layer; Wherein: the concentration of the amino-containing polymer in the mixture is 1~2 mg / mL; and / or, The pH of the mixture is 8-9; and / or, The mixing rate is 150~250 rpm; and / or, The mixing time is 1 to 3 hours.

15. A solid-state battery, characterized in that, It includes the negative electrode sheet as described in any one of claims 6 to 8, or the negative electrode sheet prepared by the method described in any one of claims 9 to 14.

16. An electrical appliance, characterized in that, Including the solid-state battery as described in claim 15.

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