Silicon-based negative electrode material for solid-state battery and preparation method of silicon-based negative electrode material

Abstract

The invention relates to the technical field of lithium ion battery energy storage, in particular to a silicon-based negative electrode material for a solid-state battery and a preparation method of the silicon-based negative electrode material. The invention provides a nano silicon / micron silicon composite material, which comprises nano silicon and porous micron silicon balls for accommodating the nano silicon, and the porous micron silicon balls have a large number of nano-scale micropores, have ultrahigh specific surface area and can be well matched with a silicon deposition process; the porous micron silicon provides a framework and support and is responsible for contact with a solid electrolyte, and the nano silicon in pores provides reversible capacity, so that the cycling stability of the material is improved; meanwhile, nano silicon is deposited in pores, so that the electrochemical sintering phenomenon is avoided; the cycling stability of the material is further improved; the silicon-based negative electrode material adopting the nano silicon / micron silicon composite material has higher first efficiency and capacity, and also has excellent cycling stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery energy storage technology, and in particular to a silicon-based anode material for solid-state batteries and its preparation method. Background Technology

[0002] In recent years, silicon-based anode materials have attracted much attention due to their ultra-high capacity. The application of silicon-based anode materials in solid-state batteries is an important topic. Similar to liquid batteries, the volume expansion effect of silicon-based anodes is a major challenge for material application. In liquid batteries, silicon particles are typically nano-sized to reduce the volume effect. However, in solid-state batteries, due to the use of solid electrolytes, as the size of the anode particles decreases, the contact between the material and the electrolyte becomes increasingly insufficient. Micron-sized silicon, due to its larger particle size, exhibits higher initial efficiency and capacity, but also, because of its larger size, it experiences greater volume expansion during lithium insertion / extraction, making it more prone to fragmentation and leading to a sharp decline in cycle stability. As early as 2010, Trevey et al. studied the impact of silicon particle size on battery performance. They found that micron-sized silicon had significantly higher capacity and initial efficiency than nano-sized silicon, but its cycle performance declined rapidly; however, using the two materials in a certain ratio could achieve complementary effects. In 2025, Masanobu Chiku et al. mixed nano-sized and micron-sized silicon in a certain ratio, achieving complementary advantages in both capacity and cycle performance. Another problem remains with the use of nano-sized silicon. Because of the external stacking pressure in solid-state batteries, nano-silicon may regenerate chemical bonds due to stress during the lithium insertion / extraction process, leading to particle aggregation and the formation of larger particles, thus losing the advantages of nanoparticles. This phenomenon is called electrochemical sintering.

[0003] In summary, the key to applying nano-silicon to the performance of solid-state batteries is to maintain a long-term stable contact between the silicon anode and the solid electrolyte, while preventing the aggregation of silicon nanoparticles during cycling to avoid electrochemical sintering. Summary of the Invention

[0004] Purpose of the invention: In order to reduce the agglomeration of silicon nanoparticles and the occurrence of electrochemical sintering in the prior art, while maintaining a long-term stable contact between the silicon anode and the solid electrolyte, this application provides a silicon-based anode material for solid-state batteries and a method for preparing the same.

[0005] In a first aspect, this application provides a silicon-based anode material, including a nano-silicon / micro-silicon composite material and a carbon coating layer on the nano-silicon / micro-silicon composite material substrate;

[0006] The nano-silicon / micro-silicon composite material includes porous micro-silicon spheres and nano-silicon deposited in the micropores of the porous micro-silicon spheres, wherein the mass ratio of nano-silicon to porous micro-silicon spheres is 0.1-0.5:1;

[0007] The micropore volume ratio of the porous micron-sized silicon spheres is 70-97%.

[0008] Preferably, the mass ratio of the nano-silicon to the porous micron-sized silicon spheres is 0.3-0.5:1.

[0009] Preferably, the micropore volume ratio in the porous micron-sized silicon spheres is 75%-97%.

[0010] Optionally, the pore volume of the porous micron-sized silicon spheres is 0.3-0.75 cm³. 3 / g, specific surface area is 1000-1600 m² 2 / g.

[0011] Preferably, the porous micron-sized silicon spheres have a pore volume of 0.55-0.75 cm³. 3 / g, specific surface area is 1400-1600 m² 2 / g.

[0012] Optionally, the carbon coating layer in the silicon-based anode material accounts for 1-10% of the total mass.

[0013] Preferably, the carbon coating layer has a mass ratio of 5%-7%.

[0014] Secondly, this application provides a method for preparing a silicon-based anode material, comprising the following preparation steps:

[0015] The silicon source material is dissolved in deionized water, and then a mineralizing agent is added to carry out a hydrothermal reaction to obtain porous silica spheres.

[0016] Porous silica spheres and micron-sized magnesium powder were mixed and heated to reduce the mixture to obtain porous micron-sized silica spheres containing magnesium metal. After acid washing and water washing, the spheres were ready for use.

[0017] Porous micron-sized silicon spheres were purged with silicon source gas in a nitrogen and high-temperature atmosphere to perform vapor phase deposition, thereby obtaining nano-silicon / micron-sized silicon composite materials.

[0018] Next, a carbon source gas is introduced to perform carbon coating on the nano-silicon / micro-silicon composite substrate at high temperature.

[0019] Optionally, the mass ratio of magnesium powder to porous silica spheres is 1.2-10:1; the particle size of the magnesium powder is 0.1-300 μm.

[0020] Preferably, the mass ratio of magnesium powder to porous silica spheres is 1.2-1.8:1, and the particle size of the magnesium powder is 100-180 μm.

[0021] Optionally, the silicon source material is any one or a combination of several of the following: silicon powder, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, methyltriethoxysilane, and oligomeric siloxane.

[0022] The mineralizing agent is any one or more combinations of potassium fluoride, potassium sodium fluoride, and potassium hydroxide.

[0023] The silicon source gas is one or a mixture of several of the following: silane, silane, silicon tetrachloride, and SiHCl3.

[0024] The carbon source is one or a combination of methane, ethane, acetylene, and propylene.

[0025] Optionally, the hydrothermal reaction temperature is 150-250 ℃ and the reaction time is 12-48 h; preferably, the hydrothermal reaction temperature is 180-220 ℃ and the reaction time is 24-30 h.

[0026] Optionally, the temperature of the vapor deposition is 400-800 ℃; preferably, the silicon deposition temperature is 500-600 ℃.

[0027] Beneficial effects: 1. This application provides a nano-silicon / micro-silicon composite material, which includes nano-silicon and porous micro-silicon spheres containing nano-silicon. The porous micro-silicon spheres have a large number of micron-sized pores and have an ultra-high specific surface area, which can be well matched with the silicon deposition process. The porous micro-silicon provides a framework and support, and is responsible for contact with the solid electrolyte. The nano-silicon in the pores provides reversible capacity and improves the cycling stability of the material. At the same time, the nano-silicon deposited in the pores avoids the occurrence of electrochemical sintering, further improving the cycling stability of the material. This makes the silicon-based anode material using the nano-silicon / micro-silicon composite material have higher initial efficiency and capacity, while also having excellent cycling stability. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the silicon-based anode material obtained by the preparation method of Example 2 of the present invention. Detailed Implementation

[0029] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1: A multi-silicon-based anode material for solid-state lithium-ion batteries, comprising the following preparation steps:

[0031] Preparation of porous micron-sized silicon spheres:

[0032] 1) The silicon source material is dissolved in deionized water, then a mineralizing agent is added, and the mixture is transferred to a hydrothermal reactor for a hydrothermal reaction to obtain porous silica spheres. During the reaction, the mineralizing agent inhibits the growth of silica crystals, creating intergranular pores.

[0033] 2) Porous micronized silica spheres and micronized magnesium powder are mixed and then heated to reduce the mixture to obtain porous micronized silica spheres containing magnesium metal. The role of the micronized magnesium powder is to maintain the pore structure of the porous silica.

[0034] 3) Acid washing and water washing of the above product to obtain the target product, porous micron-sized silicon spheres.

[0035] Optionally, in the porous micron-sized silicon spheres, the mass ratio of nano-silicon powder to micron-sized silicon powder can be any ratio between 10% and 50%, and preferably, the ratio of micron-sized silicon powder to nano-silicon powder is any ratio between 30% and 40%.

[0036] The micropore ratio of the porous micron-sized silicon spheres is 70%-97%, preferably 75%-97%.

[0037] Porous micron-sized silicon spheres require high pore volume and specific surface area. The pore volume of porous micron-sized silicon spheres ranges from 0.3 to 0.75 cm³. 3 / g; preferably, the pore volume of the material is 0.55-0.75 cm³. 3 / g. The specific surface area of ​​the material is 1000-1600 m². 2 / g; preferably, the specific surface area of ​​the material is 1400-1600 m². 2 / g.

[0038] Optionally, the silicon source material may be one or a mixture of several of the following: silicon powder, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), tetrabutyl orthosilicate (TBOS), methyltriethoxysilane (MTES), and oligomeric siloxanes.

[0039] An optional method for producing porous micron-sized silicon spheres involves dissolving silicon powder or a silicon source (such as silicate materials) in deionized water, mixing it with a mineralizing agent, and then transferring the mixture to a hydrothermal reactor. The reactor is heated to a specified temperature for reaction. During the reaction, the mineralizing agent inhibits the growth of silicon dioxide crystals, creating intercrystalline pores. These intercrystalline pores form micropores with a diameter of 2 nm to 10 nm. Under the high temperature and pressure environment of the hydrothermal reactor, the material spontaneously forms micron-sized spheres. After cooling, the spheres are filtered and washed with water to obtain porous silicon dioxide spheres with micropores. These porous silicon dioxide spheres can then be mixed with magnesium powder and reduced at high temperature to obtain porous micron-sized silicon spheres.

[0040] The mineralizing agent is one or more of potassium fluoride (KF), potassium sodium fluoride, potassium hydroxide (KOH), etc.

[0041] Optionally, the hydrothermal reaction temperature can be any temperature between 150-250℃. The preferred hydrothermal reaction temperature range is 180-220℃. Specifically, the optimal reaction time is related to the addition of a mineralizing agent and the target porosity. The reaction time can be any time between 12h and 48h. To ensure a suitable spherical size, the preferred reaction time is 24h-30h.

[0042] During the preparation of porous silica spheres by magnesothermic reduction, the large amount of heat released during the reaction may cause pore collapse. This invention strictly controls the particle size of the magnesium powder. The particle size range of the magnesium powder is 0.1 μm to 300 μm. The preferred particle size is 100-200 μm. The mass ratio of magnesium powder to porous silica spheres ranges from 1.2:1 to 10:1. The preferred ratio range is 1.2:1 to 1.8:1.

[0043] Optionally, the magnesia reaction product can be acid-washed with dilute hydrochloric acid or dilute nitric acid. Finally, after washing with water to remove the acid, porous micron-sized silicon spheres with rich micropores are obtained.

[0044] Preparation of silicon-based anode materials:

[0045] 1) Place suitable porous micron-sized silicon spheres in a CVD furnace. Heat to the target temperature under a nitrogen atmosphere.

[0046] 2) Introduce silicon source gas in a certain proportion. Perform vapor deposition at high temperature. Stop gas introduction after saturation.

[0047] 3) Introduce carbon source gas in a certain proportion and perform carbon coating at high temperature.

[0048] Optionally, a method for preparing silicon-based anode materials involves placing a certain amount of porous micron-sized silicon spheres in a rotary kiln or fluidized bed CVD deposition equipment, heating them to a target temperature under a nitrogen atmosphere, and then introducing a certain amount of silicon source gas to decompose the silicon source gas, preparing nano-silicon powder, which is then deposited inside the porous silicon pores. After silane deposition is complete, carbon source gas is introduced for carbon coating.

[0049] The silicon source gas is one or a mixture of several of the following: silane, disilane, silicon tetrachloride (SiCl4), and SiHCl3. The silicon deposition temperature is 400-800 ℃. Preferably, the silicon deposition temperature is 500-600 ℃.

[0050] The carbon source is one or a mixture of several organic gases such as methane, ethane, acetylene, and propylene. The mass ratio of carbon coating is 1%-10%, with a preferred carbon coating ratio of 5%-7%.

[0051] Optionally, a method for preparing porous carbon anode sheets is as follows: A certain amount of binder is dissolved in water and stirred continuously until the solution becomes a clear, transparent gel. Then, an appropriate amount of silicon-based anode material and conductive carbon black are added. After stirring continuously until fully mixed, the material is uniformly coated onto copper foil. Then, it is placed in a vacuum oven and dried at 80°C for 12 hours. It is then cut into sheets for later use.

[0052] Example 2: A method for preparing a silicon-based anode material for a solid-state battery, comprising the following preparation steps:

[0053] 1) Dissolve 2 g NaF in 150 ml of deionized water, then add 50 g of silicon powder and stir until dissolved. Place the solution in a reaction vessel. Calcinate the reaction vessel at 220 °C for 24 h to obtain silica microspheres with intercrystalline pores.

[0054] 2) Mix 50g of silica microspheres with intergranular pores with 60g of micron-sized magnesium powder (particle size: 150 μm), place in a rotary kiln, and heat to 800 ℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1MHCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80 ℃ for 12 h to obtain porous micron-sized silica spheres with micropores. The specific surface area of ​​these micron-sized silica spheres is 1400 m². 2 / g, with micropores accounting for approximately 97% of the volume.

[0055] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace and introduce silane gas at 600 °C, where the decomposed nano-silicon accounts for 35 wt% of the micron-sized silicon spheres. The silane flow rate is 0.5 L / min, and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane gas supply and maintain the temperature for 30 min to obtain the nano-silicon / micron-sized silicon composite material.

[0056] 4) After step 3 is completed, acetylene gas is introduced at a flow rate of 0.5 L / min for 100 min to obtain a silicon-based anode material suitable for solid-state batteries. Its scanning electron microscope image is shown below. Figure 1 .

[0057] Example 3, a method for preparing a silicon-based anode material for a solid-state battery, differs from Example 2 in that, in step 3), silane gas, comprising 10 wt% of the decomposed nano-silicon in the micron-sized silicon spheres, is introduced; the specific operation steps are as follows:

[0058] 1) Dissolve 2g NaF in 150ml deionized water, then add 50g silica powder and stir until dissolved. Place the solution in a reaction vessel. Calcinate the reaction vessel at 220℃ for 24h to obtain silica microspheres with intercrystalline pores.

[0059] 2) Mix 50g of silica microspheres with intergranular pores with 60g of micron-sized magnesium powder (particle size: 150 μm), place in a rotary kiln, and heat to 800℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1M HCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80℃ for 12 h to obtain microporous silica microspheres. The specific surface area of ​​these silica microspheres is 1400 m². 2 / g, with micropores accounting for approximately 97% of the volume.

[0060] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace at 600 degrees Celsius. Introduce silane gas containing 10 wt% of the decomposed nano-silicon from the micron-sized silicon spheres. The silane flow rate is 0.5 L / min, and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane inlet and maintain the temperature for 30 min.

[0061] 4) After step 3 is completed, switch to acetylene gas with a flow rate of 0.5 L / min and continue to supply gas for 100 min to obtain silicon-based anode material suitable for solid-state batteries.

[0062] Example 4: A method for preparing a silicon-based anode material for a solid-state battery, differing from Example 2 in that, in step 1), methyl orthosilicate (TMOS) is used to replace silicon powder in an equal amount, and the calcination temperature is 180°C; in step 3), silane gas, comprising 30 wt% of the decomposed nano-silicon in the micron-sized silicon spheres, is introduced; the specific operation steps are as follows:

[0063] 1) Dissolve 2g NaF in 150ml deionized water, then add 50g TMOS and stir until dissolved. Place the solution in a reaction vessel. Calcinate the reaction vessel at 180℃ for 24h to obtain porous silica spheres with intercrystalline pores.

[0064] 2) Mix 50g of porous silica spheres with intergranular pores with 60g of magnesium powder (particle size: 150 μm), place in a rotary kiln, and heat to 800℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1M HCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80℃ for 12 h to obtain microporous silicon spheres. The specific surface area of ​​these microporous silicon spheres is 1200 m². 2 / g, with a micropore volume ratio of 84%.

[0065] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace. At 600 °C, introduce silane gas with a decomposed nano-silicon content of 30 wt% of the micron-sized silicon spheres. The silane flow rate is 0.5 L / min and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane gas supply and keep the furnace at this temperature for 30 min.

[0066] 4) After step 3 is completed, switch to acetylene gas with a flow rate of 0.5 L / min and continue to supply gas for 100 min to obtain silicon-based anode material suitable for solid-state batteries.

[0067] Example 5: A method for preparing a silicon-based anode material for a solid-state battery, differing from Example 2 in that, in step 1), tert-butyl orthosilicate (TBOS) is used to replace silicon powder in an equal amount, and the calcination temperature is 180℃ for 36 hours; in step 3), silane gas is introduced, with the decomposed nano-silicon comprising 25 wt% of the micron-sized silicon spheres; the specific operation steps are as follows:

[0068] 1) Dissolve 2g NaF in 150ml deionized water, then add 50g TBOS and stir until dissolved. Place the solution in a reaction vessel. Calcinate the reaction vessel at 180℃ for 36h. Porous silica spheres with intergranular pores are obtained.

[0069] 2) Mix 50g of porous silica spheres with intergranular pores with 60g of micron-sized magnesium powder (particle size: 150 μm), place in a rotary kiln, and heat to 800℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1MHCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80℃ for 12 h to obtain microporous silica spheres. The specific surface area of ​​these micron-sized silica spheres is 1000 m². 2 / g, with micropores accounting for 89% of the volume.

[0070] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace and introduce silane gas with a 25% nano-silicon mass fraction at 600 °C. The silane flow rate is 0.5 L / min, and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane gas supply and maintain the temperature for 30 min.

[0071] 4) After step 3 is completed, switch to acetylene gas at a flow rate of 0.5 L / min for 100 min. This yields a silicon-based anode material suitable for solid-state batteries.

[0072] Example 6: A method for preparing a silicon-based anode material for a solid-state battery, differing from Example 2 in that, in step 1), methyltriethoxysilane (MTES) is used to replace silicon powder in an equal amount, and the calcination temperature is 180°C for 36 hours; in step 3), silane gas is introduced, with the decomposed nano-silicon comprising 40 wt% of the micron-sized silicon spheres. The specific operating steps are as follows:

[0073] 1) Dissolve 2g of NaF in 150ml of deionized water, then add 50g of MTES and stir until dissolved. Place the solution in a reaction vessel. Calcinate the reaction vessel at 180℃ for 36h to obtain porous silica spheres with intergranular pores and mesopores. Since MTES contains an organic network, the defects after removing the organic network eventually form mesopores. Accordingly, the preparation temperature and time also need to be adjusted.

[0074] 2) Mix 50g of porous silica spheres with intergranular pores and mesopores with 60g of micron-sized magnesium powder (particle size: 150 μm), place in a rotary kiln, and heat to 800℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1M HCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80℃ for 12 h to obtain microporous silica spheres; the specific surface area of ​​these silica spheres is 1500 m². 2 / g.

[0075] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace. At 600 °C, introduce silane gas containing 40 wt% nano-silicon (after decomposition) of the micron-sized silicon. The silane flow rate is 0.5 L / min, and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane gas supply and maintain the temperature for 30 min.

[0076] 4) After step 3 is completed, switch to acetylene gas with a flow rate of 0.5 L / min and continue to supply gas for 100 min to obtain silicon-based anode material suitable for solid-state batteries.

[0077] Example 7: A method for preparing a silicon-based anode material for a solid-state battery, differing from Example 2 in that, in step 1), KF is used to replace NaF in an equal amount; and in step 3), silane gas, comprising 50 wt% of the decomposed nano-silicon in the micron-sized silicon spheres, is introduced. The specific operating steps are as follows:

[0078] 1) Dissolve 2g of KF in 150ml of deionized water, then add 50g of silica powder and stir until dissolved. Place the solution in a reaction vessel. Calcine the reaction vessel at 220℃ for 24 hours. Porous silica spheres with intergranular pores are obtained. KF has a stronger inhibitory effect on crystal bonding, resulting in larger intergranular pores and larger pore sizes in the material.

[0079] 2) Mix 50g of porous silica spheres with intergranular pores with 60g of micron-sized magnesium powder (particle size: 150 μm), place in a rotary kiln, and heat to 800℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1MHCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80℃ for 12 h to obtain microporous silica spheres. The specific surface area of ​​these silica spheres is 1600 m².2 / g, with micropores accounting for approximately 97% of the volume.

[0080] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace and introduce silane gas at 600 ℃, with the decomposed nano-silicon comprising 50 wt% of the micron-sized silicon spheres; the silane flow rate is 0.5 L / min and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane gas supply and maintain the temperature for 30 min.

[0081] 4) After step 3 is completed, switch to acetylene gas with a flow rate of 0.5 L / min and continue to supply gas for 100 min to obtain silicon-based anode material suitable for solid-state batteries.

[0082] Example 8: A method for preparing a silicon-based anode material for a solid-state battery, differing from Example 2 in that, in step 1), KF is used to replace NaF in an equal amount; and in step 3), silane gas, comprising 30 wt% of the decomposed nano-silicon in the micron-sized silicon spheres, is introduced. The specific operating steps are as follows:

[0083] 1) Dissolve 2g of KF in 150ml of deionized water, then add 50g of silica powder and stir until dissolved. Place the solution in a reaction vessel. Calcine the reaction vessel at 220℃ for 24h. Porous silica spheres with intergranular pores are obtained.

[0084] 2) Mix 50g of porous silica spheres with intergranular pores with 60g of micron-sized magnesium powder (particle size: 150 μm), place in a rotary kiln, and heat to 800℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1MHCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80℃ for 12 h to obtain microporous silica spheres; the specific surface area of ​​these silica spheres is 1600 m². 2 / g, with micropores accounting for approximately 97% of the volume.

[0085] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace and introduce silane gas at 600 °C, where the decomposed nano-silicon comprises 30 wt% of the micron-sized silicon spheres. The silane flow rate is 0.5 L / min, and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane gas supply and maintain the temperature for 30 min.

[0086] 4) After step 3 is completed, switch to acetylene gas at a flow rate of 0.5 L / min for 100 min. This yields a silicon-based anode material suitable for solid-state batteries.

[0087] Example 9 describes a method for preparing a silicon-based anode material for a solid-state battery. The difference from Example 2 is that 50g of silica microspheres with intergranular pores are mixed with 100g of micron-sized magnesium powder (particle size: 200 μm). Due to the collapse of the pores in the micron-sized silicon spheres during mixing, the proportion of nano-silicon deposition decreases.

[0088] 1) Dissolve 2 g NaF in 150 ml of deionized water, then add 50 g of silicon powder and stir until dissolved. Place the solution in a reaction vessel. Calcinate the reaction vessel at 220 °C for 24 h to obtain silica microspheres with intercrystalline pores.

[0089] 2) Mix 50g of silica microspheres with intergranular pores with 200g of micron-sized magnesium powder (particle size: 200 μm), place in a rotary kiln, and heat to 800 ℃ under an argon atmosphere. Hold at this temperature for 160 min to allow the reaction to proceed fully. Wash the product with 1M HCl for 16 h. Then filter and rinse with sufficient deionized water. Dry in a vacuum drying oven at 80 ℃ for 12 h to obtain porous micron-sized silica spheres with micropores. The specific surface area of ​​these micron-sized silica spheres is 1400 m². 2 / g, with micropores accounting for approximately 97% of the volume.

[0090] 3) Place the micron-sized silicon spheres from step 2 in a CVD rotary furnace and introduce silane gas at 600 °C, where the decomposed nano-silicon accounts for 35 wt% of the micron-sized silicon spheres. The silane flow rate is 0.5 L / min, and the nitrogen flow rate is 0.5 L / min. After completion, stop the silane gas supply and maintain the temperature for 30 min to obtain the nano-silicon / micron-sized silicon composite material.

[0091] 4) After step 3 is completed, switch to acetylene gas with a flow rate of 0.5 L / min and continue to supply gas for 100 min to obtain silicon-based anode material suitable for solid-state batteries.

[0092] Application Example 1: An all-solid-state battery, comprising the following fabrication process:

[0093] Take 990 mg of the silicon-based anode material obtained in Example 2 above, 10 mg of polytetrafluoroethylene binder, disperse them in 2 ml of N-methylpyrrolidone 9 organic solvent, stir thoroughly and evenly, coat the mixture onto copper foil, and then vacuum dry at 100°C to obtain the anode sheet. The silicon anode loading in the anode is 2 mg / cm³. 2 .

[0094] Then, high-voltage lithium cobalt oxide and solid electrolyte lithium phosphorus sulfur chloride (Li6PS5Cl) were ground evenly at a mass ratio of 7:3 and mixed to form the positive electrode. Li6PS5Cl was used as the solid electrolyte and assembled with the above-obtained negative electrode to form an all-solid-state battery. The N / P ratio of the battery was controlled to be ~1.1, and the cycle performance was tested in the range of 2.5V-4.4V. The results are shown in Table 1.

[0095] Application Examples 2 to 8 are all-solid-state batteries, which differ from Application Example 1 in that they use silicon-based anode materials obtained in Examples 3 to 9 in sequence.

[0096] The difference between Comparative Example 1 and Application Example 2 is that the composite silicon anode material is replaced with 5 μm silicon particles.

[0097] The difference between Comparative Example 2 and Application Example 2 is that the composite silicon anode material is replaced with a mixture of micron-sized silicon with an average particle size of 5 μm and nano-sized silicon powder (average particle size of about 20 nm), with a ratio of micron-sized silicon to nano-sized silicon of 7:3.

[0098] Performance testing:

[0099] Table 1. Performance list of micron-sized silicon spheres and all-solid-state batteries using the silicon-based anode material of this application.

[0100] Sample Name Mass ratio of nano-silicon to porous micron-sized silicon spheres <![CDATA[Pore volume (cm 3 / g) of the porous micro - silicon spheres]]> <![CDATA[Specific surface area of micro - silicon spheres (m 2 / g)]]> Volume percentage of micropores in micron-sized silicon spheres / % mass percentage of carbon coating in silicon-based anode materials / % Capacity (mAh / g) First-efficiency of materials (%) Capacity retention rate after 100 laps (%) Application Example 2 0.35:1 0.55 1400 97 6 2695 88.3 83 Application Example 3 0.1:1 0.55 1400 97 6 2436 83.5 42 Application Example 4 0.3:1 0.43 1200 84 6 2203 87.2 56 Application Example 5 0.25:1 0.32 1000 89 5 2065 85.7 53 Application Example 6 0.4:1 0.72 1500 75 7 2550 89.1 60 Application Example 7 0.5:1 0.74 1600 97 7 2865 86.3 51 Application Example 8 0.3:1 0.74 1600 97 6 2406 83.6 56 Application Example 9 0.35:1 0.55 1400 97 6 1630 63.2 43 Application Comparative Example 1 0 \ none \ \ 3330 75.4 65 Application Comparative Example 2 0.428:1 \ none \ \ 1580 85.6 32

[0101] In this application, micropores refer to pores with a diameter in the range of 2nm-10nm; intermediate pores refer to pores with a diameter in the range of 10nm-50nm.

[0102] As shown in Table 1, in Comparative Example 2, simply mixing nano-silicon and micron-silicon effectively improves the first-cycle efficiency and capacity retention after 100 cycles. However, this improvement is more of a compromise, with relatively low capacity retention and capacity after 100 cycles. In Comparative Example 3, the first-cycle efficiency decreased from 85.6% for micron-silicon to 80.2%, while the capacity retention after 100 cycles increased from 32% to 64%. This level is only comparable to that of nano-silicon. This is mainly because simply stacking nano-silicon cannot overcome the electrochemical sintering phenomenon.

[0103] This application successfully suppressed electrochemical sintering by binding nano-silicon with the pores of micron-sized silicon. Furthermore, the porous silicon framework itself has a high porosity, facilitating ion transport while also mitigating some volume expansion. This resulted in a synergistic effect where the initial efficiency and cycling stability of the material were greater than the sum of their parts, with the initial efficiency reaching a maximum of 88.3% and the cycling stability reaching 83% after 100 cycles.

[0104] The doping ratio of nano-silicon powder to micro-silicon powder in this material is a very important parameter: In Example 3 (compared to Application Example 2), reducing the amount of nano-silicon deposition led to a significant decrease in the material's first-time efficiency and cycle stability. This indicates that the presence of nano-silicon is crucial for improving cycle stability. On the other hand, the amount of silicon deposition is also affected by the pore structure of porous carbon. In Examples 4-5 (compared to Application Examples 3-4), due to the choice of silicon source, the specific surface area of ​​the porous micro-silicon spheres was too low to support sufficient nano-silicon, resulting in limited material performance. In Example 6 (compared to Application Example 5), because the MTES used contained an organic network, the defects after removing the organic network eventually formed mesopores. The formation of mesopores is beneficial for enriching the pore structure of the material, facilitating ion transport, and improving the first-time efficiency. However, due to the increase in a large number of mesopores, the accumulation of nano-silicon in the material became uncontrollable, and the ability to inhibit electrochemical sintering was weakened, resulting in reduced cycle stability. Examples 7 and 8 (compared to Application Examples 6-7) encountered similar situations. Due to the choice of mineralizer, the pore size of the intergranular pores was too large, and the cycle stability of the material was not ideal.

[0105] Through the above embodiments, the porous carbon-supported nano-silicon anode provided by the present invention exhibits better electrochemical performance. These embodiments are merely preferred embodiments of the present invention.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon-based anode material, characterized in that, This includes nano-silicon / micro-silicon composite materials and carbon coating layers on nano-silicon / micro-silicon composite material substrates; The nano-silicon / micro-silicon composite material includes porous micro-silicon spheres and nano-silicon deposited in the micropores of the porous micro-silicon spheres, wherein the mass ratio of nano-silicon to porous micro-silicon spheres is 0.1-0.5:

1. The micropore volume ratio of the porous micron-sized silicon spheres is 70-97%.

2. The silicon-based anode material according to claim 1, characterized in that, The mass ratio of the nano-silicon to the porous micron-sized silicon spheres is 0.3-0.5:

1.

3. A silicon-based anode material according to claim 1 or 2, characterized in that, The micropore volume ratio of the porous micron-sized silicon spheres is 75%-97%.

4. The silicon-based anode material according to claim 3, characterized in that, The porous micron-sized silicon spheres have a pore volume of 0.3-0.75 cm³. 3 / g, specific surface area is 1000-1600 m² 2 / g.

5. A silicon-based anode material according to claim 4, characterized in that, The porous micron-sized silicon spheres have a pore volume of 0.55-0.75 cm³. 3 / g, specific surface area is 1400-1600 m² 2 / g.

6. A silicon-based anode material according to any one of claims 1-2, 4-5, characterized in that, The carbon coating has a mass ratio of 1-10%.

7. A method for preparing the silicon-based anode material according to any one of claims 1-6, characterized in that, The preparation steps include the following: The silicon source material is dissolved in deionized water, and then a mineralizing agent is added to carry out a hydrothermal reaction to obtain porous silica spheres. Porous silica spheres and micron-sized magnesium powder were mixed and heated to reduce the mixture to obtain porous micron-sized silica spheres containing magnesium metal. After acid washing and water washing, the spheres were ready for use. Porous micron-sized silicon spheres were purged with silicon source gas in a nitrogen and high-temperature atmosphere to perform vapor phase deposition, thereby obtaining nano-silicon / micron-sized silicon composite materials. Next, a carbon source gas is introduced to perform carbon coating on the nano-silicon / micro-silicon composite substrate at high temperature.

8. The method for preparing a silicon-based anode material according to claim 7, characterized in that, The mass ratio of magnesium powder to porous silica spheres is 1.2-10:1; the particle size of the magnesium powder is 0.1-300 μm.

9. The method for preparing a silicon-based anode material according to claim 8, characterized in that, The mass ratio of magnesium powder to porous silica spheres is 1.2-1.8:1, and the particle size of the magnesium powder is 100-180 μm.

10. A method for preparing a silicon-based anode material according to any one of claims 7-9, characterized in that, The silicon source material is any one or a combination of several of the following: silicon powder, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, methyltriethoxysilane, and oligomeric siloxane. The mineralizing agent is any one or more combinations of potassium fluoride, potassium sodium fluoride, and potassium hydroxide. The silicon source gas is one or a mixture of several of the following: silane, silane, silicon tetrachloride, and SiHCl3. The carbon source is one or a combination of methane, ethane, acetylene, and propylene.

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