Silicon-based negative electrode active material and preparation method thereof, silicon-based negative electrode active material and application thereof, and solid-state battery

Abstract

The invention provides a silicon-based negative electrode active material and a preparation method thereof, a silicon-based negative electrode active material and application thereof, and a solid-state battery, and is characterized in that the silicon-based negative electrode active material comprises porous nanometer silicon and N-CNTs and TiN loaded on the surface of the porous nanometer silicon; wherein the particle size of the porous nano silicon is 20-100nm, and the specific surface area of the porous nano silicon is 20-100m < 2 > / g; the silicon-based negative electrode active material prepared by the invention has electrochemical stability, good structural stability and good conductivity, and the silicon-based negative electrode active material prepared by using the silicon-based negative electrode active material has higher negative electrode active material proportion, higher charge-discharge specific capacity and higher first-circle coulombic efficiency in a solid-state battery; according to the present invention, the prepared lithium ion battery has characteristics of low energy consumption and long cycle life, the capacity retention rate after 200 cycles can achieve more than 90%, the impedance change amount after 200 cycles is low, and the excellent capacity retention capacity is represented at different multiplying powers of 0.5-5C.

Description

Technical Field

[0001] This invention relates to the field of silicon-based anode technology, specifically to a silicon-based anode active material and its preparation method, silicon-based anode active materials and their applications, and solid-state batteries. Background Technology

[0002] Silicon is an alloy-type lithium intercalation material. Unlike currently available commercial graphite anodes that store lithium through an intercalation mechanism, silicon reacts with lithium to form Li through an alloying reaction. x Si alloy. Pure silicon has a theoretical specific capacity of up to 4200 mAh / g, and is abundant, safe and non-toxic. It is regarded as an important transitional solution from traditional graphite anodes to lithium metal anodes in all-solid-state battery anode systems.

[0003] Silicon-based anodes offer significant advantages but also present challenges that need to be overcome in the application of all-solid-state batteries. Silicon's ultra-high theoretical specific capacity (approximately 10 times that of graphite) can significantly increase the upper limit of energy density in all-solid-state batteries. The high mechanical strength of the solid electrolyte can, to some extent, physically constrain the enormous volume expansion (>300%) of silicon particles during charging and discharging, helping to maintain the structural integrity of the silicon-based anode and suppress pulverization. Furthermore, the all-solid-state system does not use liquid electrolytes, avoiding the continuous reaction between silicon and liquid electrolytes that consumes active lithium and generates gas, mitigating interfacial side reactions, and thus improving cycle stability and safety.

[0004] However, the volume expansion, interfacial side reactions, and conductivity issues of silicon-based anodes still limit their application in all-solid-state systems. While all-solid-state systems can suppress silicon volume expansion to some extent, significant stress is still repeatedly generated during charge and discharge, leading to failure of the solid electrolyte / silicon contact interface and increased interfacial impedance. Poor electrochemical compatibility between silicon and solid electrolytes (such as sulfide electrolytes) results in interfacial side reactions or the formation of unstable space charge layers, hindering efficient lithium-ion transport. Furthermore, silicon, as a semiconductor, has poor conductivity; its low conductivity and structural changes during charge and discharge place higher demands on the construction and maintenance of the internal ion / electron conductive network of the electrode. Current technologies cannot overcome the low conductivity of silicon-based anodes, requiring an innovative approach to overcome this bottleneck. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a silicon-based anode active material and its preparation method, a silicon-based anode active material and its application, and a solid-state battery. The silicon-based anode active material prepared by the present invention has good stability, cycle life and conductivity. The silicon-based anode active material of the present invention can effectively improve the charge-discharge specific capacity and first-cycle coulombic efficiency of solid-state batteries when used in silicon-based anode active materials and solid-state batteries, and has a longer cycle life and excellent capacity retention capability.

[0006] The inventors of this invention have discovered that loading N-CNTs (nitrided carbon nanotubes) and TiN onto the surface of porous nano-silicon with specific particle size and specific surface area can effectively improve the stability, cycle life, and conductivity of silicon-based anode active materials. Analysis suggests that, on the one hand, TiN forms a tight coating layer on the surface of porous nano-silicon, resulting in a core-shell self-pressurizing structure that suppresses the expansion of the silicon-based anode. On the other hand, the TiN layer effectively isolates the direct contact between the sulfide electrolyte and the porous nano-silicon, and provides conductive channels and structural support for the porous nano-silicon, thereby improving the electrochemical stability of the silicon-based anode. Further analysis indicates that TiN binds to the porous nano-silicon via Ti-Si bonds, forming a Si-TiN structure on the surface of the porous nano-silicon. N-CNTs are interspersed within the Si-TiN structure, tightly bound to the Ti-N bonds through the van der Waals forces at the nitrogen modification sites, synergistically constructing a three-dimensional conductive network to further suppress the expansion of the silicon-based anode. Moreover, the composite three-dimensional network structure also synergistically improves the ion / electron transport efficiency of N-CNTs, thereby enhancing the conductivity of the active material of the silicon-based anode.

[0007] Based on the above research, in a first aspect, the present invention provides a silicon-based anode active material, wherein the silicon-based anode material comprises porous nano-silicon (such as... Figure 1 ) and N-CNTs (nitrided carbon nanotubes) and TiN loaded on the porous nano-silicon surface; The porous nano-silicon has a particle size of 20-100 nm and a specific surface area of ​​20-100 m². 2 / g.

[0008] In a preferred embodiment of the present invention, the molar ratio of porous nano-silicon to TiN is 1-5:1, preferably 3-5:1. Analysis suggests that this preferred molar ratio allows TiN to be uniformly loaded onto the surface of the porous nano-silicon particles, promoting rapid diffusion of lithium ions between the solid phases, effectively suppressing the volume expansion and pulverization of the porous nano-silicon, and providing structural support, thus significantly improving the cycle life of the silicon-based anode active material. Simultaneously, the TiN coating effectively isolates the sulfide electrolyte from direct contact with the porous nano-silicon, enhancing the electrochemical stability of the silicon-based anode.

[0009] In a preferred embodiment of the present invention, the total amount of porous nano-silicon and TiN to N-CNTs is in a mass ratio of 100:300:1, preferably 150-250:1. This preferred molar ratio further suppresses the expansion of the silicon-based anode and improves the conductivity of the active material in the silicon-based anode.

[0010] In a preferred embodiment of the present invention, the porous nano-silicon has a particle size of 30-70 nm; and / or, the porous nano-silicon has a specific surface area of ​​50-80 m².2 / g; and / or, the tap density of the porous nano-silicon is 0.4-0.8 g / cm³. 3 The preferred value is 0.5-0.75 g / cm³. 3 .

[0011] In a preferred embodiment of the present invention, the method for preparing the porous nano-silicon structure includes: mixing porous microspheres of SiO2 with Mg under an inert atmosphere and reacting the mixture to obtain a Si-containing mixture; then acid-washing the obtained Si-containing mixture to obtain porous nano-silicon. The porous nano-silicon prepared by this preferred method can effectively buffer the volume changes of silicon-based anode active materials during charge and discharge, thereby improving structural stability.

[0012] In a preferred embodiment of the present invention, the porous microsphere SiO2 has a particle size of 40-120 nm, preferably 40-100 nm. Analysis suggests that this preferred porous microsphere SiO2 can effectively suppress the volume expansion of silicon-based anode active materials, thereby improving the stability and electrical performance of the silicon-based anode active materials.

[0013] In a preferred embodiment of the present invention, the molar ratio of the porous microspheres of SiO2 to Mg is 1:2-3.5.

[0014] In a preferred embodiment of the present invention, the conditions for the first reaction include: a reaction temperature of 600-700°C and a reaction time of 3-6 hours.

[0015] In a preferred embodiment of the present invention, the method for preparing porous nano-silicon further includes heating to the first reaction temperature at a rate of 5-10℃ / min in an inert atmosphere before carrying out the first reaction. In a preferred embodiment of the present invention, the pickling solution used in the pickling treatment is selected from at least one of hydrochloric acid, sulfuric acid and nitric acid, preferably hydrochloric acid.

[0016] In a preferred embodiment of the present invention, the concentration of the pickling solution is 1-3 mol / L; In a preferred embodiment of the present invention, the method for preparing porous nano-silicon further includes acid washing of a Si-containing mixture followed by drying.

[0017] The inventors of this invention have discovered that a silicon-based anode active material prepared by grinding porous nano-silicon obtained through magnesothermic reduction of a porous SiO2 template with nano-TiO2, reacting the resulting material, and then mixing and grinding it with nitride-modified carbon nanotubes can possess both excellent stability and conductivity. Analysis suggests that magnesothermic reduction of a silica template can prepare porous nano-silicon. Then, reacting the porous nano-silicon and nano-TiO2 in a mixed atmosphere containing NH3 yields a TiN layer, a nitride material Si-TiN with Si-Ti bonds loaded on the surface of the porous nano-silicon. On one hand, TiN forms a tight coating layer on the surface of the nano-silicon, resulting in a core-shell self-pressurizing structure that suppresses the expansion of the silicon-based anode. On the other hand, the TiN layer effectively isolates the sulfide electrolyte from direct contact with the porous nano-silicon and provides conductive channels and structural support for the porous nano-silicon, thereby improving the electrochemical stability of the silicon-based anode. Then, N-CNTs are mixed and ground with Si-TiN nitride material having the above structure, which allows N-CNTs to be interspersed in the Si-TiN structure. Through the van der Waals forces between the nitrogen modification sites and Ti-N bonds, they are tightly bound together to synergistically construct a three-dimensional conductive network, which further suppresses the expansion of silicon-based anode. Moreover, the three-dimensional network structure formed by the composite also synergistically improves the ion / electron transport efficiency of N-CNTs, thereby improving the conductivity of silicon-based anode active material.

[0018] Based on the above research, in a second aspect, the present invention provides a method for preparing a silicon-based negative electrode active material, the preparation method comprising the following steps: Step S1: Under an inert atmosphere, porous microspheres of SiO2 are mixed with Mg and subjected to a first reaction to obtain a mixture containing Si. Step S2: The Si-containing mixture obtained in step S1 is acid-washed to obtain porous nano-silicon (e.g., Figure 1 ); Step S3: Under an inert gas atmosphere, in a solvent, the porous nano-silicon and nano-TiO2 obtained in step S2 are mixed and ground to obtain the ground material; Step S4: In a mixed atmosphere of inert gas and NH3, the ground material obtained in step S3 is subjected to a second reaction to obtain the nitrided material Si-TiN; Step S5: Mix and grind N-CNTs and Si-TiN nitride obtained in step S4 to obtain silicon-based anode active material.

[0019] In a preferred embodiment of the present invention, the porous microsphere SiO2 has a particle size of 40-120 nm, preferably 50-100 nm.

[0020] In a preferred embodiment of the present invention, in step S1, the inert gas is selected from at least one of Ar, Ne, He and Kr, preferably Ar.

[0021] In a preferred embodiment of the present invention, in step S1, the molar ratio of the porous microspheres SiO2 to Mg is 1:2-3.5.

[0022] In a preferred embodiment of the present invention, in step S1, the conditions for the first reaction include: a reaction temperature of 600-700℃ and a reaction time of 3-10h.

[0023] In a preferred embodiment of the present invention, step S1 further includes heating the material to the temperature of the first reaction at a rate of 2-10°C / min in an inert atmosphere before the first reaction, preferably at a rate of 3-7°C / min.

[0024] In a preferred embodiment of the present invention, in step S2, the pickling solution used in the pickling treatment is selected from at least one of hydrochloric acid, sulfuric acid and nitric acid, preferably hydrochloric acid; more preferably, the concentration of the pickling solution is 0.5-3 mol / L, preferably 0.5-2 mol / L.

[0025] In a preferred embodiment of the present invention, step S2 further includes acid washing of a Si-containing mixture followed by drying to obtain porous nano-silicon.

[0026] In a preferred embodiment of the present invention, in step S3, the inert gas is selected from at least one of Ar, Ne, He and Kr, preferably Ar.

[0027] In a preferred embodiment of the present invention, in step S3, the solvent is selected from at least one of ethanol, isopropanol, acetone and toluene.

[0028] In a preferred embodiment of the present invention, in step S3, the molar ratio of the porous nano-silicon to nano-TiO2 is 2-6:1, preferably 3.5-5:1. Using this preferred ratio can further improve the electrical performance of the silicon-based anode active material. Analysis suggests that the load layer formed using this preferred ratio is more conducive to lithium-ion transport.

[0029] In a preferred embodiment of the present invention, in step S3, the amount of solvent used is 0.5-10 mL relative to 1 mol of porous nano-silicon.

[0030] In a preferred embodiment of the present invention, in step S3, the particle size of the nano-TiO2 is 3-6 nm.

[0031] In a preferred embodiment of the present invention, in step S4, the inert gas is selected from at least one of Ar, Ne, He and Kr, preferably Ar.

[0032] In a preferred embodiment of the present invention, in step S4, the volume of NH3 is 30%-60% of the total volume of inert gas and NH3, preferably 40%-60%.

[0033] In a preferred embodiment of the present invention, in step S4, the conditions for the second reaction include: a reaction temperature of 800-1200℃, preferably 1050-1200℃; and a reaction time of 1-6 hours, preferably 2-5 hours. Using these preferred second reaction conditions can effectively improve the stability of the silicon-based anode active material. Analysis suggests that these preferred second reaction conditions are more conducive to TiN loading, thereby more effectively suppressing the volume expansion of porous nano-silicon.

[0034] In a preferred embodiment of the present invention, in step S4, the rate of introduction of the mixed gas of inert gas and NH3 is 50-200 mL / min, preferably 120-180 mL / min.

[0035] In a preferred embodiment of the present invention, step S4 of the preparation method further includes heating the material to the temperature of the second reaction in an inert gas atmosphere at a heating rate of 2-10°C / min before carrying out the second reaction, preferably heating the material to the temperature of the second reaction in an inert gas atmosphere at a heating rate of 3-7°C / min.

[0036] In a preferred embodiment of the present invention, in step S4, before the second reaction, the inert gas is introduced at a rate of 50-200 mL / min, preferably at a rate of 80-120 mL / min.

[0037] In a preferred embodiment of the present invention, step S5 involves calcining CNTs in a mixed atmosphere of inert gas and NH3 to obtain N-CNTs.

[0038] In a preferred embodiment of the present invention, in the method for preparing N-CNTs, the inert gas is selected from at least one of Ar, Ne, He and Kr, preferably Ar.

[0039] In a preferred embodiment of the present invention, in the preparation method of the N-CNTs, the volume of NH3 is 10%-60% of the total volume of the inert gas and NH3, preferably 15%-30%. Analysis suggests that using this preferred volume ratio effectively avoids the introduction of nitrogen defects into the N-CNTs and prevents damage to the integrity of the tube wall structure, thereby further improving the electrical performance and stability of the silicon-based anode active material.

[0040] In a preferred embodiment of the present invention, the calcination conditions in the preparation method of the N-CNTs include: a calcination temperature of 700-900℃, preferably 750-850℃; and a calcination time of 1-6 hours, preferably 2-5 hours. Analysis suggests that these preferred calcination conditions effectively increase the number of active nitrogen sites, which is beneficial for enhancing the interfacial bonding between N-CNTs and TiN, thereby forming a highly efficient conductive pathway and improving the electrical performance and stability of the silicon-based anode active material.

[0041] In a preferred embodiment of the present invention, in the method for preparing N-CNTs, the rate of introduction of the mixed gas of inert gas and NH3 is 50-150 mL / min, preferably 80-120 mL / min.

[0042] In a preferred embodiment of the present invention, the method for preparing the N-CNTs further includes heating to the calcination temperature in an inert gas atmosphere at a heating rate of 2-10°C / min before calcination, preferably heating to the calcination temperature in an inert gas atmosphere at a heating rate of 3-7°C / min.

[0043] In a preferred embodiment of the present invention, in the method for preparing N-CNTs, before calcination, the inert gas is introduced at a rate of 10-200 mL / min, preferably at a rate of 50-150 mL / min.

[0044] In a preferred embodiment of the present invention, in step S5, the weight ratio of the Si-TiN nitride obtained in step S4 to the N-CNTs is 100-300:1, preferably 150-250:1. In a preferred embodiment of the present invention, the porous nano-silicon obtained in step S2 has a particle size of 20-100 nm, preferably 30-70 nm, and a specific surface area of ​​20-100 m². 2 / g, preferably 50-80m 2 / g; tap density is 0.4-0.8 g / cm³ 3 The preferred concentration is 0.5-0.7 g / cm³. 3 .

[0045] In a preferred embodiment of the present invention, in step S5, the obtained silicon-based anode material includes porous nano-silicon and N-CNTs and TiN loaded on the surface of the porous nano-silicon.

[0046] In a preferred embodiment of the present invention, the molar ratio of porous nano-silicon to TiN in the obtained silicon-based anode material is 1-5:1, preferably 3-5:1.

[0047] In a preferred embodiment of the present invention, the total amount of porous nano-silicon and TiN to N-CNTs in the obtained silicon-based anode material is 100-300:1, preferably 150-250:1.

[0048] In a preferred embodiment of the present invention, the inert gas in steps S1, S3, S4 and S5 is Ar.

[0049] Thirdly, the present invention provides a silicon-based anode material, the silicon-based anode material comprising a sulfide electrolyte and the silicon-based anode active material described in the first aspect or prepared by the preparation method described in the second aspect.

[0050] In a preferred embodiment of the present invention, the sulfide electrolyte is Li6PS5Cl.

[0051] In a preferred embodiment of the present invention, the mass ratio of the silicon-based negative electrode active material to the sulfide electrolyte is 65-75:25-35.

[0052] In a preferred embodiment of the present invention, the silicon-based anode material is prepared by grinding raw materials including silicon-based anode active material and sulfide electrolyte in an inert gas atmosphere.

[0053] Fourthly, the present invention provides the application of the silicon-based anode active material described in the first aspect, the silicon-based anode active material prepared by the preparation method described in the second aspect, or the silicon-based anode material described in the third aspect in the field of all-solid-state batteries.

[0054] Fifthly, the present invention provides a solid-state battery, the solid-state battery comprising a silicon-based negative electrode sheet, a sulfide electrolyte layer and a lithium indium counter electrode, wherein the silicon-based negative electrode sheet comprises the silicon-based negative electrode material described in the third aspect.

[0055] In this invention, the assembly method of the solid-state battery is a conventional method in the art, and will not be described in detail here.

[0056] The beneficial effects of this invention are at least in the following aspects: Firstly, TiN is coated onto the surface of nano-silicon to form a tight coating layer, resulting in a core-shell self-pressurizing structure. This suppresses the expansion of the silicon-based anode, avoids direct contact between the sulfide electrolyte and the nano-silicon, and improves the cycle life of the silicon-based anode.

[0057] Secondly, N-CNTs are interspersed in Si-TiN and are tightly bound to Ti-N bonds through the van der Waals forces at the nitrogen modification sites, synergistically constructing a three-dimensional conductive network. This can further suppress the expansion of the silicon-based anode, and the composite three-dimensional network structure also synergistically improves the ion / electron transport efficiency of N-CNTs. In the preparation of silicon-based anode materials, there is no need to add additional conductive agents to obtain better conductivity, thereby increasing the proportion of active material in silicon-based anode materials. Attached Figure Description

[0058] Figure 1 This is a morphology diagram of the porous silicon nanoparticles in Example 1.

[0059] Figure 2 These are cycle life curves for Example 1 and Comparative Examples 1-3. Detailed Implementation

[0060] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0061] The following electrolyte layer, lithium indium counter electrode, and all-solid-state mold battery were prepared using conventional methods in the art.

[0062] Sulfide electrolyte layer: In an inert gas atmosphere, the sulfide electrolyte is spread flat in a PEEK tube, and a pressure of 100 MPa is applied and held for 2 minutes to form the layer.

[0063] Lithium-indium counter electrode: In an inert gas atmosphere, a lithium sheet with a diameter of 6 mm and a thickness of 50 μm and an indium sheet with a diameter of 10 mm and a thickness of 50 μm are stacked in a PEEK tube, and a pressure of 100 MPa is applied and held for 1 min to form the electrode.

[0064] All-solid-state mold battery: Silicon-based negative electrode material is laid flat on one side of the electrolyte membrane with the current collector facing outward and centered in an inert gas atmosphere. Lithium-indium counter electrode is placed on the other side of the electrolyte membrane with the lithium side facing outward and centered. A pressure of 200-300MPa is applied and held for 2 minutes. After pressing and molding, an all-solid-state mold battery is obtained.

[0065] Example 1 Step S1: Mix 8.5g of porous microspheres of SiO2 (particle size of 70nm) with 7g of magnesium powder evenly, place in a crucible, and heat to 650℃ at a heating rate of 5℃ / min under Ar atmosphere to carry out the first reaction. The reaction time is 6h to obtain Si-containing material powder. Step S2: After removing the Si-containing material powder, place it in 200 mL of 1 mol / L HCl solution and stir for 1 h. After repeated washing until the pH is neutral, transfer it to a 60℃ oven for drying for 12 h to obtain porous silicon nanoparticles. The particle size of the porous silicon nanoparticles was measured to be 50 nm, and the specific surface area was 60 g / m². 2 The tap density is 0.6 g / cm³. 3 .

[0066] Step S3: Take 3.4 g of porous nano-silicon particles, 2.41 g of TiO2 (particle size of 5 nm) and 0.5 mL of anhydrous ethanol, mix them and place them in a mortar. Grind them in an argon glove box for 30 min, and then transfer them to a vacuum oven at 60 °C to dry for 10 h to obtain uniformly dispersed grinding material.

[0067] Step S4: Transfer the ground material obtained in step S3 into a high-temperature tube furnace, introduce Ar atmosphere at a rate of 100 mL / min and heat to 1100℃ at a rate of 5℃ / min, then adjust to introduce NH3 / Ar (NH3:Ar=1:1) mixed atmosphere at a rate of 150 mL / min for the second reaction, the reaction time is 5 h, and the material Si-TiN is obtained by natural cooling.

[0068] Step S5: Transfer 3 g of CNTs into a high-temperature tube furnace, introduce an Ar atmosphere at a flow rate of 100 mL / min and heat to 800 °C at a heating rate of 5 °C / min. Then adjust the flow rate to 100 mL / min and introduce an NH3 / Ar (NH3:Ar=1:3) mixed atmosphere for calcination for 3 h. After natural cooling, nitrided modified carbon nanotubes (N-CNTs) are obtained. The Si-TiN and N-CNTs obtained in step S4 were mixed at a mass ratio of 200:1. The mixed material was placed in a ball mill jar and dispersed by ball milling at 300 rpm for 1 hour at a ball-to-material ratio of 20:1 to obtain silicon-based anode active material.

[0069] Step S6: Grind and mix the silicon-based anode active material and Li6PS5Cl at a mass ratio of 70:30 under an argon atmosphere for 30 minutes to obtain the silicon-based anode material.

[0070] A solid-state mold battery was assembled by using 10 mg of silicon-based anode material as the anode sheet, 85 mg of sulfide Li6PS5Cl as the intermediate electrolyte layer, and lithium indium alloy as the counter electrode.

[0071] The all-solid-state mold battery was placed in the test fixture and pressure was applied to 200MPa. This pressure was maintained for 10 hours. After the standing period, an activation cycle (one cycle) was performed at a rate of 0.05C. The test voltage window was set to -0.6V to 0.9V to complete the activation process of a single charge-discharge cycle.

[0072] Example 2 Step S1: Mix 8.5g of porous microspheres of SiO2 (particle size of 80nm) with 11g of magnesium powder evenly, place in a crucible, and heat to 600℃ at a heating rate of 3℃ / min under Ar atmosphere to carry out the first reaction. The reaction time is 10h to obtain Si-containing material powder. Step S2: After removing the Si-containing material powder, it was placed in 300 mL of 2 mol / L HCl solution and stirred for 2 h. After repeated washing until the pH was neutral, it was transferred to an 80℃ oven for drying for 8 h to obtain porous nano-silicon particles. The particle size of the porous nano-silicon particles was measured to be 70 nm, and the specific surface area was 42 g / m². 2 The tap density is 0.71 g / cm³. 3 .

[0073] Step S3: Take 3.4 g of porous nano-silicon particles, 3.24 g of TiO2 (particle size of 3 nm) and 1 mL of anhydrous ethanol, mix them and place them in a mortar. Grind them in an argon glove box for 60 min, and then transfer them to a vacuum oven at 80 °C to dry for 8 h to obtain uniformly dispersed grinding material.

[0074] Step S4: Transfer the ground material obtained in step S3 into a high-temperature tube furnace, introduce Ar atmosphere at a rate of 80 mL / min and heat to 1050 °C at a rate of 3 °C / min, then adjust to introduce NH3 / Ar (NH3:Ar=2:3) mixed atmosphere at a rate of 120 mL / min for the second reaction, the reaction time is 5 h, and the material Si-TiN is obtained by natural cooling.

[0075] Step S5: Transfer 3 g of CNTs into a high-temperature tube furnace, introduce an Ar atmosphere at a flow rate of 50 mL / min and heat to 900 °C at a heating rate of 7 °C / min, then adjust to introduce an NH3 / Ar (NH3:Ar=3:7) mixed atmosphere at a flow rate of 80 mL / min and calcine for 1 h, and then naturally cool to obtain nitrided modified carbon nanotubes (N-CNTs). The Si-TiN and N-CNTs obtained in step S4 were mixed at a mass ratio of 150:1. The mixed material was placed in a ball mill jar and dispersed by ball milling at 200 rpm for 5 hours at a ball-to-material ratio of 10:1 to obtain silicon-based anode active material.

[0076] Step S6: Grind and mix the silicon-based anode active material and Li6PS5Cl at a mass ratio of 70:30 under an argon atmosphere for 60 minutes to obtain the silicon-based anode material.

[0077] A solid-state mold battery was assembled by using 10 mg of silicon-based anode material as the anode sheet, 85 mg of sulfide Li6PS5Cl as the intermediate electrolyte layer, and lithium indium alloy as the counter electrode.

[0078] The all-solid-state mold battery was placed in the test fixture and pressure was applied to 200MPa. This pressure was maintained for 10 hours. After the standing period, an activation cycle (one cycle) was performed at a rate of 0.05C. The test voltage window was set to -0.6V to 0.9V to complete the activation process of a single charge-discharge cycle.

[0079] Example 3 Step S1: Mix 8.5g of porous microsphere SiO2 (particle size 33nm) with 6.8g of magnesium powder evenly, place in a crucible, and heat to 700℃ at a heating rate of 7℃ / min under Ar atmosphere to carry out the first reaction. The reaction time is 3h to obtain Si-containing material powder. Step S2: After removing the Si-containing material powder, place it in 100 mL of 0.5 mol / L HCl solution and stir for 0.5 h. After repeated washing until the pH is neutral, transfer it to a 50℃ oven for drying for 18 h to obtain porous nano-silicon particles. The particle size of the porous nano-silicon particles was measured to be 30 nm, and the specific surface area was 80 g / m². 2 The tap density is 0.53 g / cm³. 3 .

[0080] Step S3: Take 3.4 g of porous nano-silicon particles, 2 g of TiO2 (particle size of 6 nm) and 0.3 mL of anhydrous ethanol, mix them and place them in a mortar. Grind them in an argon glove box for 20 min, and then transfer them to a vacuum oven at 50 °C to dry for 18 h to obtain uniformly dispersed grinding material.

[0081] Step S4: Transfer the ground material obtained in step S3 into a high-temperature tube furnace, introduce Ar atmosphere at 120 mL / min and heat to 1200℃ at a heating rate of 7℃ / min, then adjust to introduce NH3 / Ar (NH3:Ar=3:2) mixed atmosphere at 180 mL / min for the second reaction, the reaction time is 2 h, and the material is naturally cooled to obtain Si-TiN nitride.

[0082] Step S5: Transfer 3 g of CNTs into a high-temperature tube furnace, introduce an Ar atmosphere at a flow rate of 150 mL / min and heat to 700 °C at a heating rate of 3 °C / min, then adjust to introduce an NH3 / Ar (NH3:Ar=3:17) mixed atmosphere at a flow rate of 120 mL / min and calcine for 6 h, and then naturally cool to obtain nitrided modified carbon nanotubes (N-CNTs). The Si-TiN and N-CNTs obtained in step S4 were mixed at a mass ratio of 250:1. The mixed material was placed in a ball mill jar and dispersed by ball milling at 200 rpm for 5 hours at a ball-to-material ratio of 10:1 to obtain silicon-based anode active material.

[0083] Step S6: Grind and mix the silicon-based anode active material and Li6PS5Cl at a mass ratio of 70:30 under an argon atmosphere for 20 minutes to obtain the silicon-based anode material.

[0084] A solid-state mold battery was assembled by using 10 mg of silicon-based anode material as the anode sheet, 85 mg of sulfide Li6PS5Cl as the intermediate electrolyte layer, and lithium indium alloy as the counter electrode.

[0085] The all-solid-state mold battery was placed in the test fixture and pressure was applied to 200MPa. This pressure was maintained for 10 hours. After the standing period, an activation cycle (one cycle) was performed at a rate of 0.05C. The test voltage window was set to -0.6V to 0.9V to complete the activation process of a single charge-discharge cycle.

[0086] Example 4 The silicon-based negative electrode active material and the all-solid-state mold battery were prepared according to the preparation method of Example 1, except that in step S4, the temperature was increased to 1000°C at a heating rate of 5°C / min in an Ar atmosphere of 100 mL / min.

[0087] Example 5 The silicon-based negative electrode active material and the all-solid-state mold battery were prepared according to the preparation method of Example 1, except that in step S4, the temperature was increased to 900°C at a heating rate of 5°C / min in an Ar atmosphere of 100 mL / min.

[0088] Example 6 The silicon-based negative electrode active material and the all-solid-state mold battery were prepared according to the preparation method of Example 1. The difference was that in step S5, an NH3 / Ar atmosphere of 100 mL / min was introduced and the reaction was continued for 3 h (the volume ratio of NH3 to Ar was 1:2).

[0089] Example 7 The silicon-based negative electrode active material and the all-solid-state mold battery were prepared according to the preparation method of Example 1, except that the amount of TiO2 used in step S3 was 2.91 g.

[0090] Example 8 The silicon-based negative electrode active material and the all-solid-state mold battery were prepared according to the preparation method of Example 1, except that in step S5, the temperature was increased to 700°C at a heating rate of 5°C / min in an Ar atmosphere of 100 mL / min.

[0091] Example 9 The silicon-based negative electrode active material and the all-solid-state mold battery were prepared according to the preparation method of Example 1, except that the particle size of the porous microsphere SiO2 in step S1 was 1 μm.

[0092] Comparative Example 1 The all-solid-state mold battery was assembled according to the preparation method of Example 1, except that the nano-silicon and artificial graphite (compacted density 1.5 g / cm³) obtained in step S2 were used. 3 The materials (particles with a particle size of 20 nm) were mixed at a mass ratio of 1:6. The mixed materials were placed in a ball mill jar and dispersed by ball milling at 300 rpm for 1 hour at a ball-to-material ratio of 20:1 to obtain silicon-based anode active material.

[0093] In step S6, the silicon-based anode active material is ground and mixed for 30 minutes under an argon atmosphere according to the mass ratio of silicon-based anode active material: Li6PS5Cl: VGCF = 70:30:1 to obtain the silicon-based anode material.

[0094] VGCF is vapor-grown carbon fiber used as a conductive agent.

[0095] Comparative Example 2 Silicon-based anode active material and all-solid-state mold battery were prepared according to the preparation method of Example 1, except that step S5 was not performed. In step S6, the silicon-based anode active material is ground and mixed for 30 minutes under an argon atmosphere according to the mass ratio of silicon-based anode active material: Li6PS5Cl: VGCF = 70:30:1 to obtain the silicon-based anode material.

[0096] VGCF is vapor-grown carbon fiber used as a conductive agent.

[0097] Comparative Example 3 Silicon-based anode active material and all-solid-state mold battery were prepared according to the preparation method of Example 1, except that steps S3 and S4 were not performed. In step S5, the porous nano-silicon obtained in step S2 is mixed with N-CNTs at a mass ratio of 200:1. The mixed material is placed in a ball mill jar and dispersed by ball milling at 300 rpm for 1 hour at a ball-to-material ratio of 20:1 to obtain silicon-based anode active material.

[0098] Comparative Example 4 Silicon-based anode active material and all-solid-state mold battery were prepared according to the preparation method of Example 1, except that step S4 was not performed. In step S5, the grinding material obtained in step S3 is mixed with N-CNTs at a mass ratio of 200:1. The mixed material is placed in a ball mill jar and dispersed by ball milling at 300 rpm for 1 hour at a ball-to-material ratio of 20:1 to obtain silicon-based anode active material.

[0099] Comparative Example 5 Silicon-based anode active material and all-solid-state mold battery were prepared according to the preparation method of Example 1, except that carbon nanotubes were not nitrided in step S5. In step S6, the nitride material obtained in step S4 and carbon nanotubes are mixed and ground to obtain a silicon-based anode active material.

[0100] Comparative Example 6 The silicon-based anode active material and the all-solid-state mold battery were prepared according to the preparation method of Example 1, with the following differences: In step S3, 3.4 g of porous silicon nanoparticles, 3 g of carbon nanotubes and 0.5 mL of anhydrous ethanol were mixed and placed in a mortar. The mixture was ground in an argon glove box for 30 min and then transferred to a vacuum oven at 60 °C for 10 h to obtain uniformly dispersed ground material. Step S4: Transfer the ground material obtained in step S3 into a high-temperature tube furnace, heat it to 1100°C in an Ar atmosphere at a heating rate of 5°C / min, and continue the reaction for 5 hours with an NH3 / Ar atmosphere at a heating rate of 150 mL / min (NH3:Ar=1:1). After natural cooling, the nitrided material is obtained. 2.41 g TiO2 was transferred to another high-temperature tube furnace and heated to 1100 °C at a heating rate of 5 °C / min in an Ar atmosphere of 100 mL / min. The reaction was continued for 5 h with an NH3 / Ar atmosphere of 150 mL / min (NH3:Ar=1:1). After natural cooling, TiN was obtained. Step S5: Mix the nitrided material obtained in step S4 with TiN at a mass ratio of 200:1. Place the mixed material in a ball mill jar and disperse it by ball milling at 300 rpm for 1 hour at a ball-to-material ratio of 20:1 to obtain silicon-based anode active material.

[0101] Comparative Example 7 Silicon-based anode active material and all-solid-state mold battery were prepared according to the preparation method of Example 1, except that step S3 was not performed.

[0102] Step S4: 2.41 g of nano TiO2 was transferred into a high-temperature tube furnace and heated to 1100 °C at a heating rate of 5 °C / min in an Ar atmosphere of 100 mL / min. The reaction was continued for 5 h with an NH3 / Ar atmosphere of 150 mL / min (NH3:Ar=1:1). After natural cooling, TiN was obtained. Step S5: Transfer 3 g of CNTs into a high-temperature tube furnace and heat to 800°C at a heating rate of 5°C / min in an Ar atmosphere of 100 mL / min. Then, introduce an NH3 / Ar atmosphere of 100 mL / min and continue the reaction for 3 h (NH3:Ar=1:3). After natural cooling, nitrided modified carbon nanotubes (N-CNTs) are obtained. The porous silicon nanoparticles obtained in step S2 and the TiN obtained in step S4 were mixed and then mixed with N-CNTs at a mass ratio of 200:1. The mixed material was placed in a ball mill jar and dispersed by ball milling at 300 rpm for 1 hour at a ball-to-material ratio of 20:1 to obtain silicon-based anode active material.

[0103] Step S6: Grind and mix the silicon-based anode active material and Li6PS5Cl at a mass ratio of 70:30 under an argon atmosphere for 30 minutes to obtain the silicon-based anode material.

[0104] Comparative Example 8 Silicon-based anode active material and all-solid-state mold battery were prepared according to the preparation method of Example 1, except that in step S1, porous microsphere SiO2 was replaced with an equal weight of amorphous SiO2.

[0105] Test Example 1 The porous silicon nanoparticles obtained in step S2 of Example 1 were subjected to scanning electron microscopy (SEM) to obtain morphology images of the porous silicon nanoparticles. (See attached image.) Figure 1 .

[0106] Test Example 2 The all-solid-state mold batteries assembled in the above embodiments and comparative examples were tested. The voltage window was set to -0.6V to 0.9V, and 0.5C charge-discharge cycle tests were performed. An impedance test was conducted every 100 cycles to obtain the first-cycle charge-discharge data (charge specific capacity and discharge specific capacity) (see Table 1), the first-cycle coulombic efficiency data (see Table 1), and the impedance data (see Table 2). The cycle life curves for Example 1 and Comparative Examples 1-3 are shown in Table 2. Figure 2 .

[0107] Test Example 3 The above embodiments and comparative examples were used to assemble all-solid-state mold batteries for rate performance testing. The test voltage window was set to -0.6V to 0.9V, and the rate performance tests were conducted at 0.5C, 1C, 3C, and 5C rates (see Table 3).

[0108] Table 1

[0109] Table 2

[0110] Table 3

[0111] As shown in Tables 1-3, the all-solid-state mold battery assembled using the silicon-based anode active material of the present invention exhibits the following characteristics during 0.5C charge-discharge cycle testing and impedance testing every 100 cycles: first-cycle charge specific capacity exceeding 1519 mAh / g, discharge specific capacity exceeding 1696 mAh / g, and first-cycle coulombic efficiency exceeding 87%; pre-test impedance as low as 45 Ω, impedance after 100 cycles as low as 61 Ω, impedance after 200 cycles as low as 100 Ω, and 5C rate performance exceeding 866. This demonstrates that the silicon-based anode active material of the present invention possesses excellent stability, cycle life, and conductivity. The all-solid-state mold battery assembled using this material exhibits high charge-discharge specific capacity and first-cycle coulombic efficiency, as well as long cycle life and excellent capacity retention.

[0112] The all-solid-state mold battery assembled using the silicon-based anode active material of the preferred embodiments 1-3 of this invention exhibits the following characteristics in 0.5C charge-discharge cycle tests and impedance tests every 100 cycles: first-cycle charge specific capacity exceeding 1694 mAh / g, first-cycle discharge specific capacity exceeding 1782 mAh / g, and first-cycle coulombic efficiency exceeding 91.6%; pre-test impedance as low as 39 Ω, impedance after 100 cycles as low as 54 Ω, impedance after 200 cycles as low as 85 Ω, and 5C rate performance exceeding 935 mAh / g. This demonstrates that the preferred silicon-based anode active material of this invention possesses better stability, cycle life, and conductivity, resulting in all-solid-state mold batteries with higher charge-discharge specific capacity and first-cycle coulombic efficiency, as well as longer cycle life and excellent capacity retention.

[0113] Compared to the silicon-based anode active material prepared in step S4 of Example 5 by heating to 900°C in an Ar atmosphere at a heating rate of 5°C / min, the silicon-based anode active material prepared in step S4 of Example 1 by introducing an Ar atmosphere at a rate of 100 mL / min and heating to 1100°C at a heating rate of 5°C / min can effectively improve the charge and discharge performance of the all-solid-state mold battery (the charge specific capacity can be increased to 1730.3 mAh / g, and the discharge specific capacity can be increased to 1872.6 mAh). / g, the first-cycle coulombic efficiency can be improved to 92.4%) and rate performance (0.5C rate performance can be improved to 1377.3mAh / g, 1C rate performance can be improved to 1340.1mAh / g, 3C rate performance can be improved to 1211.5mAh / g, and 5C rate performance can be improved to 1050.6mAh / g), and it also effectively reduces the impedance data of the all-solid-state mold battery (the impedance before testing can be reduced to 38Ω, the impedance after 100 cycles can be reduced to 52Ω, and the impedance after 200 cycles can be reduced to 77Ω).

[0114] Compared to step S3 in Example 7, where the amount of TiO2 used was 2.91 g, in step S3 of Example 1 of the present invention, the amount of TiO2 used was 2.41 g. The prepared silicon-based anode active material can effectively improve the charge and discharge performance of the all-solid-state mold battery (charge specific capacity can be increased to 1730.3 mAh / g, discharge specific capacity can be increased to 1872.6 mAh / g, and first-cycle coulombic efficiency can be increased to 92.4%) and rate performance (0.5C rate performance can be increased to 1377.3 mAh / g, 1C rate performance can be increased to 1340.1 mAh / g, 3C rate performance can be increased to 1211.5 mAh / g, and 5C rate performance can be increased to 1050.6 mAh / g). It also effectively reduces the impedance data of the all-solid-state mold battery (the impedance before testing can be reduced to 38 Ω, the impedance after 100 cycles can be reduced to 52 Ω, and the impedance after 200 cycles can be reduced to 77 Ω). This indicates that the silicon-based anode active material prepared in Example 1 of the present invention has better stability, cycle life, and conductivity.

[0115] Compared to Comparative Example 1, which involves a simple physical mixing of nano-silicon and artificial graphite, Example 1, prepared using the method of this invention, significantly improves the charge-discharge performance and rate performance of the all-solid-state mold battery, and also significantly reduces the impedance data. Analysis suggests that this process is a typical preparation method for traditional silicon-carbon anodes. Compared to the system of Example 1, the electrochemical performance of Comparative Example 1 is lower than that of Example 1, demonstrating the superiority of the process in Example 1.

[0116] Compared to Comparative Example 2, which omits step S5, Example 1 of the present invention significantly improves the charge / discharge performance and rate performance of the all-solid-state mold battery, and also significantly reduces the impedance data of the all-solid-state mold battery. Analysis suggests that the method of the present invention can synergistically construct a three-dimensional conductive network containing N-CNTs and TiN, thereby effectively suppressing the expansion of the silicon-based anode. Furthermore, the composite three-dimensional network structure synergistically improves the ion / electron transport efficiency of N-CNTs, thereby enhancing the conductivity of the silicon-based anode active material.

[0117] Compared to Comparative Example 4, which omits step S4, Example 1 of the present invention significantly improves the charge-discharge performance and rate performance of the all-solid-state mold battery, and also significantly reduces the impedance data of the all-solid-state mold battery. Analysis suggests that in the present invention, the synergistic effect of the formed TiN and N-CNTs can more significantly improve the conductivity and stability of the silicon-based anode active material, showing advantages over TiO2.

[0118] Compared to Comparative Example 5, which used undoped CNTs, Example 1 of this invention, employing nitrogen-doped N-CNTs, significantly improves the charge-discharge performance and rate performance of the all-solid-state mold battery, and also significantly reduces the impedance data of the all-solid-state mold battery. Analysis suggests that nitrogen-modified N-CNTs can form a strong interfacial bond with TiN, enabling the construction of a coherent three-dimensional conductive network, thereby effectively improving the electrical performance and stability of the silicon-based anode active material.

[0119] Compared to Comparative Example 8, which used amorphous SiO2, the silicon-based negative electrode active material prepared by porous microsphere SiO2 in Example 1 can effectively improve the charge and discharge performance (charge specific capacity can be increased to 1730.3 mAh / g, discharge specific capacity can be increased to 1872.6 mAh / g, and first-cycle coulombic efficiency can be increased to 92.4%) and rate performance (0.5C rate performance can be increased to 1377.3 mAh / g, 1C rate performance can be increased to 1340.1 mAh / g, 3C rate performance can be increased to 1211.5 mAh / g, and 5C rate performance can be increased to 1050.6 mAh / g) of the all-solid-state mold battery. Moreover, it can effectively reduce the impedance data of the all-solid-state mold battery (the impedance before measurement can be reduced to 38 Ω, the impedance after 100 cycles can be reduced to 52 Ω, and the impedance after 200 cycles can be reduced to 77 Ω). Analysis suggests that using porous microspheres of SiO2 can effectively suppress the volume expansion of silicon-based anode active materials, thereby improving the stability of silicon-based anode active materials.

[0120] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A silicon-based anode active material, characterized in that, The silicon-based anode active material includes porous nano-silicon and N-CNTs and TiN loaded on the surface of the porous nano-silicon; The porous nano-silicon has a particle size of 20-100 nm and a specific surface area of ​​20-100 m². 2 / g.

2. The silicon-based anode active material according to claim 1, characterized in that, The molar ratio of the porous nano-silicon to TiN is 1-5:1, preferably 3-5:1; And / or, the total amount of the porous nano-silicon and TiN to the mass ratio of N-CNTs is 100-300:1, preferably 150-250:1; And / or, the porous nano-silicon has a particle size of 30-70 nm and a specific surface area of ​​50-80 m². 2 / g; And / or, the tap density of the porous nano-silicon is 0.4-0.8 g / cm³. 3 The preferred value is 0.5-0.75 g / cm³. 3 ; And / or, the method for preparing the porous nano-silicon includes: mixing porous microspheres of SiO2 with Mg under an inert atmosphere and then carrying out a first reaction to obtain a Si-containing mixture, and then acid washing the obtained Si-containing mixture to obtain porous nano-silicon; Preferably, the porous microsphere SiO2 has a particle size of 40-120 nm, more preferably 40-100 nm; And / or, the molar ratio of the porous microspheres of SiO2 to Mg is 1:2-3.5; And / or, the conditions for the first reaction include: a reaction temperature of 600-700℃ and a reaction time of 3-6h; And / or, the method for preparing the porous nano-silicon further includes heating to the temperature of the first reaction at a rate of 5-10 °C / min in an inert atmosphere before carrying out the first reaction; And / or, the pickling solution used in the pickling treatment is selected from at least one of hydrochloric acid, sulfuric acid and nitric acid, preferably hydrochloric acid; Preferably, the concentration of the pickling solution is 1-3 mol / L; And / or, the method for preparing the porous nano-silicon further includes acid washing of the Si-containing mixture followed by drying.

3. A method for preparing a silicon-based negative electrode active material, characterized in that, The preparation method includes the following steps: Step S1: Under an inert atmosphere, porous microspheres of SiO2 are mixed with Mg and subjected to a first reaction to obtain a mixture containing Si. Step S2: The Si-containing mixture obtained in step S1 is acid-washed to obtain porous nano-silicon; Step S3: Under an inert gas atmosphere, in a solvent, the porous nano-silicon and nano-TiO2 obtained in step S2 are mixed and ground to obtain the ground material; Step S4: In a mixed atmosphere of inert gas and NH3, the ground material obtained in step S3 is subjected to a second reaction to obtain the nitrided material Si-TiN; Step S5: Mix and grind N-CNTs and Si-TiN nitride obtained in step S4 to obtain silicon-based anode active material.

4. The preparation method according to claim 3, characterized in that, In step S1, the particle size of the porous microsphere SiO2 is 40-120 nm, preferably 50-100 nm; And / or, in step S1, the inert gas is selected from at least one of Ar, Ne, He and Kr, preferably Ar; And / or, in step S1, the molar ratio of the porous microspheres of SiO2 to Mg is 1:2-3.5; And / or, in step S1, the conditions for the first reaction include: a reaction temperature of 600-700℃ and a reaction time of 3-10h; And / or, in step S1, the preparation method further includes, before carrying out the first reaction, heating to the temperature of the first reaction at a rate of 2-10°C / min in an inert atmosphere, preferably at a rate of 3-7°C / min. And / or, in step S2, the pickling solution used in the pickling treatment is selected from at least one of hydrochloric acid, sulfuric acid and nitric acid, preferably hydrochloric acid; Preferably, the concentration of the pickling solution is 0.5-3 mol / L, and more preferably 0.5-2 mol / L; And / or, in step S2, the preparation method further includes acid washing of the Si-containing mixture followed by drying to obtain porous nano-silicon; And / or, in step S3, the inert gas is selected from at least one of Ar, Ne, He and Kr, preferably Ar; And / or, in step S3, the solvent is selected from at least one of ethanol, isopropanol, acetone and toluene; And / or, in step S3, the molar ratio of the porous nano-silicon to nano-TiO2 is 2-6:1, preferably 3.5-5:1; And / or, in step S3, the amount of solvent used is 0.5-10 mL relative to 1 mol of porous nano-silicon; And / or, in step S3, the particle size of the nano-TiO2 is 3-6 nm.

5. The preparation method according to claim 3 or 4, characterized in that, In step S4, the inert gas is selected from at least one of Ar, Ne, He and Kr, preferably Ar; And / or, in step S4, the volume of NH3 is 30%-60% of the total volume of the inert gas and NH3, preferably 40%-60%; And / or, in step S4, the conditions for the second reaction include: a reaction temperature of 800-1200℃, preferably 1050-1200℃; and a reaction time of 1-6h, preferably 2-5h. And / or, in step S4, the rate of introduction of the inert gas and NH3 mixture is 50-200 mL / min, preferably 120-180 mL / min. And / or, in step S4, the preparation method further includes heating to the temperature of the second reaction in an inert gas atmosphere at a heating rate of 2-10℃ / min before carrying out the second reaction, preferably heating to the temperature of the second reaction in an inert gas atmosphere at a heating rate of 3-7℃ / min. Preferably, in step S4, before the second reaction, the inert gas is introduced at a rate of 50-200 mL / min, and more preferably at a rate of 80-120 mL / min.

6. The preparation method according to any one of claims 3-5, characterized in that, In step S5, the method for preparing the N-CNTs includes calcining CNTs in a mixed atmosphere of inert gas and NH3 to obtain N-CNTs. Preferably, in the method for preparing N-CNTs, the inert gas is selected from at least one of Ar, Ne, He and Kr, and preferably Ar; And / or, in the method for preparing the N-CNTs, the volume of NH3 is 10%-60% of the total volume of the inert gas and NH3, preferably 15%-30%; And / or, in the method for preparing the N-CNTs, the calcination conditions include: a calcination temperature of 700-900℃, preferably 750-850℃; and a calcination time of 1-6h, preferably 2-5h. And / or, in the method for preparing N-CNTs, the rate of introduction of the mixed gas of inert gas and NH3 is 50-150 mL / min, preferably 80-120 mL / min; And / or, the method for preparing the N-CNTs further includes heating to the calcination temperature in an inert gas atmosphere at a heating rate of 2-10℃ / min before calcination, preferably heating to the calcination temperature in an inert gas atmosphere at a heating rate of 3-7℃ / min. Preferably, in the method for preparing N-CNTs, before calcination, the inert gas is introduced at a rate of 10-200 mL / min, and more preferably at a rate of 50-150 mL / min. And / or, in step S5, the weight ratio of the Si-TiN nitride obtained in step S4 to the N-CNTs is 100-300:1, preferably 150-250:

1.

7. The preparation method according to any one of claims 3-6, characterized in that, The porous nano-silicon obtained in step S2 has a particle size of 20-100 nm, preferably 30-70 nm; and a specific surface area of ​​20-100 m². 2 / g, preferably 50-80m 2 / g; tap density is 0.4-0.8 g / cm³ 3 The preferred concentration is 0.5-0.7 g / cm³. 3 ; And / or, in step S5, the obtained silicon-based negative electrode active material includes porous nano-silicon and N-CNTs and TiN loaded on the surface of the porous nano-silicon; And / or, in the obtained silicon-based anode active material, the molar ratio of the porous nano-silicon to TiN is 1-5:1, preferably 3-5:1; And / or, in the obtained silicon-based anode material, the total amount of porous nano-silicon and TiN to N-CNTs has a mass ratio of 100-300:1, preferably 150-250:

1.

8. A silicon-based anode material, characterized in that, The silicon-based anode material includes a sulfide electrolyte and the silicon-based anode active material as described in claim 1 or 2, or the silicon-based anode active material prepared by any one of claims 3-7; Preferably, the sulfide electrolyte is Li6PS5Cl; And / or, the mass ratio of the silicon-based negative electrode active material to the sulfide electrolyte is 65-75:25-35; And / or, the silicon-based anode material is prepared by grinding raw materials including silicon-based anode active material and sulfide electrolyte in an inert gas atmosphere.

9. The application of the silicon-based anode active material according to claim 1 or 2, the silicon-based anode active material prepared by the preparation method according to any one of claims 3-7, or the silicon-based anode material according to claim 8 in the field of all-solid-state batteries.

10. A solid-state battery, characterized in that, The solid-state battery includes the silicon-based anode material as described in claim 8, a sulfide electrolyte layer, and a lithium indium counter electrode.

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