Nano-silicon and its hot-cold closed coupling processing method and application

Abstract

This invention belongs to the field of battery materials, specifically relating to a method for hot-cold sealed coupling processing of nano-silicon. The method involves filling and sealing nano-silicon within a heat-conducting container, followed by a secondary heat transfer gradient heat treatment of the container, then rapid cooling in a cooling medium system, and finally post-processing, washing, and drying to obtain the processed nano-silicon. The gradient heat treatment process includes 2-5 heat-insulating platforms, wherein the initial heat-insulating platform temperature is 200-300℃, and the final heat-insulating platform temperature is 800-1200℃. The melting point of the container wall material is greater than or equal to 1400℃, and the thermal conductivity is greater than or equal to 100 W / m·K. This invention also includes the silicon material obtained by the above preparation method and its application in batteries. The preparation method of this invention can significantly improve the electrochemical performance of the obtained material.

Description

Technical Field

[0001] This invention belongs to the field of energy storage materials, specifically relating to the field of nano-silicon anode materials. Background Technology

[0002] Environmental and energy issues have become pressing problems for contemporary society, and new energy technologies are one of the key technologies for effectively alleviating or even solving these two major problems. The large-scale application of clean and renewable new energy sources requires effective energy storage. Typically, new energy sources are converted into electrical energy through various forms of energy conversion before utilization. Lithium-ion batteries, with their advantages of high capacity density, high single-cell voltage, and no memory effect, have become one of the fastest-growing and most widely used energy storage devices in the 21st century.

[0003] Lithium-ion batteries generally consist of a positive electrode, a negative electrode, a separator, and an electrolyte. The positive and negative electrode materials largely determine the battery's performance. Currently, the main positive electrode materials for commercially available lithium-ion batteries are lithium cobalt oxide, lithium iron phosphate, and ternary materials, while carbon-based materials are the primary negative electrode materials. Since the commercial application of lithium-ion batteries in 1992, the performance of negative electrode materials has been limited by the low theoretical capacity of graphite, and has not seen significant improvement. However, societal development has placed higher demands on the performance of lithium-ion batteries. Both electric vehicles and digital products require longer driving ranges, meaning that lithium-ion batteries need higher energy densities. Research shows that silicon currently has the highest theoretical energy density among lithium-ion battery negative electrode materials, reaching 4200 mAh / g, more than 10 times that of graphite, and is expected to become the next generation of high-performance lithium-ion battery negative electrode materials.

[0004] However, silicon as a negative electrode material for lithium-ion batteries has several drawbacks: poor conductivity, large volume changes during charge and discharge, easy electrode pulverization, structural instability, and high manufacturing costs. These problems result in extremely low initial coulombic efficiency and poor cycle performance in lithium-ion batteries, severely hindering the development and application of silicon negative electrode materials. Nanotechnology is an important means to solve these problems. By utilizing nanotechnology to reduce the volume effect of silicon materials and increase the contact area between materials, conductivity is improved, greatly enhancing the performance of silicon negative electrode materials in lithium-ion batteries.

[0005] However, existing silicon nanotechnology still has some drawbacks: First, the preparation cost is high and the production efficiency is low. Currently, the main methods for producing nano-silicon powder include dealloying, vapor deposition, and metallothermic reduction, none of which are suitable for large-scale applications. Second, although nanotechnology alleviates the volume effect of silicon during charging and discharging, this is achieved by providing a buffer space between particles, which cannot prevent the pulverization and structural collapse of silicon materials. At the same time, it also results in a very low tap density of nano-silicon powder. In addition, nanotechnology increases the specific surface area of ​​silicon particles, which partially improves the conductivity of silicon electrons and ions, but also amplifies its side reactions in lithium-ion battery systems, resulting in low coulombic efficiency and rapid battery performance degradation. Summary of the Invention

[0006] To address the shortcomings of existing methods for preparing nano-silicon, which suffer from unsatisfactory electrochemical performance, the primary objective of this invention is to provide a method for directly utilizing nano-silicon through a thermal-cold sealing coupling process. This method aims to directly modify nano-silicon and improve its electrochemical performance.

[0007] The second objective of this invention is to provide a treated nano-silicon material obtained by the preparation method described above.

[0008] A third objective of this invention is to provide an application of the treated nano-silicon material in batteries and a battery incorporating the treated nano-silicon.

[0009] There are already a few cases in the industry where nano-silicon anode materials have been applied to commercial lithium-ion batteries. The main approach is to first prepare high-purity nano-silicon powder using methods such as chemical vapor deposition or ball milling, and then combine a very small amount of nano-silicon with a large amount of graphite or other carbon materials to form a silicon-carbon composite material with slightly better performance than traditional carbon anode materials, which is then used in lithium-ion batteries. There are also methods that use ball milling to obtain silicon suboxide with lower capacity and coulombic efficiency but more stable performance, and then combine it with carbon materials for use in lithium-ion batteries. However, to date, there are no reports of a combined high-temperature heat treatment and extreme cold treatment approach that fundamentally changes the physical and chemical properties of nano-silicon anode materials and allows for their direct application in lithium-ion batteries. This invention aims to provide a method for preparing high-value, high-performance silicon materials using a thermal-cold closed-loop processing technology. However, research shows that thermal treatment of silicon nanomaterials is difficult to alter their microstructure and properties, and cold treatment is prone to irreversible side reactions with the coolant. Furthermore, the thermal-cold combined processing faces many technical challenges, making it difficult to achieve the desired results when applied to the development of high-performance silicon anode materials for lithium-ion batteries. Therefore, in the early stages of technology development, it is difficult to obtain silicon anode materials with ideal electrochemical performance. Through continuous research, this invention provides the following improved process:

[0010] A method for heat-cold sealed coupling processing of nano-silicon involves filling and sealing nano-silicon in a heat-conducting container, then subjecting the heat-conducting container to a gradient heat treatment with secondary heat transfer, followed by rapid cooling in a cooling medium system, and finally post-processing, washing, and drying to obtain the processed nano-silicon.

[0011] The gradient heat treatment process includes 2 to 5 insulation platforms, wherein the temperature of the initial insulation platform is 200 to 300°C, and the temperature of the final insulation platform is 800 to 1200°C.

[0012] The wall material of the heat-conducting container has a melting point temperature greater than or equal to 1400℃ and a thermal conductivity greater than or equal to 100W / m·K.

[0013] The application of heat treatment-rapid cooling coupled processing for nano-silicon remains a gap in the industry. This is primarily because nano-silicon exhibits high reactivity, and conventional heat treatment and rapid cooling processes easily lead to degradation of its physicochemical properties, making it impossible to successfully prepare materials with high electrochemical performance. To fill this gap, this invention, through research, has discovered that using nano-silicon as raw material and employing a secondary heat transfer gradient heat treatment process conducted by a heat-conducting container, combined with a rapid cooling process, can not only effectively overcome the degradation of nano-silicon during heat treatment-rapid cooling but also unexpectedly further adjust the phase structure and crystal occurrence mode of the material, thereby significantly improving the electrochemical performance of the treated nano-silicon material. The process described in this invention enables the direct processing of nanoscale silicon materials and yields silicon materials with excellent energy density, cycle performance, coulombic efficiency, and rate performance.

[0014] In this invention, the nano-silicon refers to silicon with a nanoscale size. Preferably, the particle size of the nano-silicon is less than or equal to 500 nm; more preferably, it is less than or equal to 300 nm; further preferably, it is 50–300 nm; and even more preferably, it is 50–100 nm.

[0015] In this invention, the nano-silicon can be obtained using existing commercial products or prepared using existing methods. For example, the nano-silicon can be obtained by ball milling elemental silicon.

[0016] Preferably, the silicon material is a particle or block with a size of micrometer or larger;

[0017] Preferably, the silicon is at least one of monocrystalline silicon, polycrystalline silicon, or amorphous silicon;

[0018] Preferably, the ball milling is a dry ball milling or a wet ball milling;

[0019] Preferably, the ball milling medium is one or more of the following: inert gases such as argon, nitrogen, and helium, or liquids such as anhydrous ethanol, ultrapure water, polyethylene glycol, and glycerol; the ball-to-material ratio in the ball milling process is 10–60:1; the ball milling speed is 100–600 r / min; and the ball milling time is 2–10 h.

[0020] In this invention, nano-silicon is pre-encapsulated in a heat-conducting container, and heat treatment and rapid cooling are carried out by the heat-conducting container wall. This allows for unexpected control of the crystal structure and morphology of the nano-silicon, and unexpected improvement of the performance of the treated nano-silicon.

[0021] In this invention, the secondary heat transfer heat treatment refers to heat treatment mediated by the wall gap of the heat-conducting container.

[0022] In this invention, the heat-conducting container is a heat-conducting container resistant to high / low temperatures.

[0023] In this invention, the wall material of the heat-conducting container is an alloy material, and more preferably one of stainless steel, aluminum alloy, copper alloy, molybdenum alloy, tungsten alloy, niobium alloy, and nickel alloy.

[0024] Preferably, the wall material of the heat-conducting container does not undergo brittle fracture at -200°C;

[0025] The nano-silicon is filled into the heat-conducting container chamber under a protective atmosphere and then sealed.

[0026] Preferably, the protective gas is at least one selected from nitrogen, inert gas, carbon dioxide, and hydrogen.

[0027] Preferably, the packing capacity of nano-silicon is greater than or equal to 50%, more preferably 50-95%.

[0028] In this invention, a heat-conducting container encapsulating nano-silicon is placed inside a heating furnace chamber, and the nano-silicon inside the heat-conducting container chamber is modified and reformed through secondary heat conduction via the heat-conducting container wall. In this invention, the heat-conducting container can be heated in a nitrogen or inert gas atmosphere.

[0029] This invention has discovered that by coupling the gradient heat treatment process with the aforementioned secondary heat transfer process and the aforementioned quenching process, it is possible to successfully link the heat treatment and quenching processes of nanoscale materials. Moreover, it is possible to unexpectedly regulate the crystal structure of nano-silicon, which is beneficial to improving its electrochemical performance.

[0030] In this invention, the gradient heat treatment can be a two-stage heat preservation process, a three-stage heat preservation process, a four-stage heat preservation process, or a five-stage heat preservation process.

[0031] Preferably, the gradient heat treatment process includes three holding stages, wherein the first holding stage is at a temperature of 200–300°C, the second holding stage is at a temperature of 500–650°C, and the third holding stage is at a temperature of 800–1200°C. This invention has found that, under the preferred secondary heat transfer gradient heat treatment, the synergy between heat treatment and rapid cooling can be unexpectedly achieved, which is beneficial for obtaining nano-silicon materials with high electrochemical performance.

[0032] Preferably, the heating rate to the first insulation temperature is 4-6℃ / min; the heating rate from the first insulation temperature to the second insulation temperature is 10-15℃ / min; and the heating rate from the second insulation temperature to the third insulation temperature is 1-3℃ / min.

[0033] Preferably, the first heat preservation time is 0.5 to 1 hour; the second heat preservation time is 1 to 2 hours; and the third heat preservation time is 2 to 4 hours.

[0034] Another preferred four-stage gradient heat treatment scheme of the present invention has the following conditions: the temperature of the first stage heat treatment is 200-300℃; the temperature of the second stage heat treatment is 350-450℃; the temperature of the third stage heat treatment is 650-750℃; and the temperature of the fourth stage heat treatment is 950-1050℃. Preferably, the temperature is first increased to the first stage heat treatment temperature at a rate of 4-6℃ / min and held for 0.5-1h; then the temperature is increased to the second stage heat treatment temperature at a rate of 4-6℃ / min and held for 1-2h; then the temperature is increased to the third stage heat treatment temperature at a rate of 10-15℃ / min and held for 1-3h; finally, the temperature is increased to the fourth stage heat treatment temperature at a rate of 1-3℃ / min and held for 1-3h, thus completing the gradient heat treatment.

[0035] In this invention, after gradient heat treatment, the heat-conducting container, which is kept in a sealed state, is directly placed in a cooling medium for rapid cooling.

[0036] Preferably, the cooling medium is a liquid cooling medium or a gaseous cooling medium;

[0037] Preferably, the cooling medium is one or more of the following: anhydrous ethanol, polyethylene glycol, deionized water, liquid nitrogen, dry ice, air, argon, and nitrogen.

[0038] Preferably, the temperature difference between the heat-conducting container and the initial cooling medium is greater than or equal to 800°C.

[0039] Preferably, the cooling rate is 10-10000℃ / min.

[0040] In this invention, after rapid cooling, post-processing and washing are performed to obtain the desired nano-silicon material.

[0041] In this invention, the post-treatment includes acid treatment, alkali treatment, or a mixture of acid treatment and alkali treatment in any order.

[0042] Preferably, the acid solution is an aqueous solution containing HF. The concentration of the acid solution is, for example, 0.1–10 mol / L, and more preferably 0.5–5 mol / L.

[0043] Preferably, the alkaline solution is an aqueous solution containing an alkali metal hydroxide; the concentration of the alkaline solution is, for example, 0.1 to 10 mol / L, and more preferably 0.5 to 5 mol / L.

[0044] Preferably, the temperature of the post-processing is 10–60°C;

[0045] Preferably, the post-treatment is followed by a water wash. The water used for the water wash can be distilled water.

[0046] Preferably, the filtrate is washed with water until the pH of the filtrate is 6.5 to 7.5.

[0047] A more specific embodiment of the present invention includes the following steps:

[0048] Step (1): The silicon material is nano-sized by high-energy ball milling to reduce its size, uniform particle size, and smooth morphology, thus obtaining nano-silicon powder;

[0049] Step (2): Fill and seal the nano-silicon powder in a thermally conductive sealed container, and then place the thermally conductive container directly in the heating chamber for gradient heat treatment;

[0050] Step (3): The heat-conducting container after heat treatment is placed directly into the cooling medium while still hot and in a sealed state for instantaneous cooling. Then, it is subjected to post-treatment, washing and drying to obtain high-performance silicon anode material for lithium-ion batteries.

[0051] By employing the high-energy ball milling nano-sizing and hot-cold sealing coupling process described in this invention, and with the synergistic control of the parameters, a silicon anode active material with uniform nano-morphology, good crystallinity, abundant defects, and stable internal microstructure can be obtained. This material can reduce the generation of "dead lithium" during the electrochemical reaction, alleviate the huge stress changes during charging and discharging, improve the coulombic efficiency during charging and discharging, and ensure the cycle performance of the silicon anode material. Furthermore, this process ensures the uniformity of the silicon anode material's performance through high-energy ball milling nano-shaping, playing a crucial role in the consistent release of lithium-ion battery performance. It also creatively employs a high / low temperature resistant alloy container sealing technology, effectively achieving the organic coupling of high-temperature heat treatment and extreme cold treatment, resulting in a "1+1>2" effect in improving material performance. The nano-silicon material prepared using this invention can also be used to composite with other materials, such as carbon materials and oxide anode materials, to prepare high-performance composite anode materials.

[0052] The present invention also provides a treated nano-silicon obtained by the preparation method described above;

[0053] Preferably, the prepared treated nano-silicon has a large number of defect structures and / or twin phases.

[0054] The particles are silicon nanoparticles with a particle size of less than or equal to 500 nm; more preferably less than or equal to 100 nm.

[0055] The present invention also provides an application of the treated nano-silicon obtained by the preparation method described above, in the preparation of batteries.

[0056] In a preferred application, it is used to prepare the negative electrode of a battery; for example, the lithium-ion battery nano-silicon negative electrode material obtained by the method is slurried with a conductive agent and a binder, coated on the surface of a current collector, and dried to obtain the battery negative electrode. The conductive agent, binder, and slurry solvent can all be materials well-known in the industry, and the methods for slurrying, coating, and drying to obtain the negative electrode can also be well-known in the industry.

[0057] Preferably, the battery is a lithium-ion battery.

[0058] The present invention also provides a lithium-ion battery comprising the treated nano-silicon obtained by the preparation method described above;

[0059] Preferably, the negative electrode contains a negative electrode material comprising the treated nano-silicon.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] This invention is the first to propose and successfully realize direct heat treatment and rapid cooling treatment of nano-silicon.

[0062] This invention directly uses nano-silicon as the treatment object, pre-filling and sealing it in a thermally conductive and high-low temperature resistant container cavity. Then, it utilizes the orderly connection and organic coupling of secondary heat transfer heat treatment by the heat conduction of the container wall and extreme cold treatment. This can achieve synergistic coupling. In addition to successfully realizing the heat treatment-rapid cooling treatment of nano-silicon, it can also unexpectedly improve the microstructure of the treated nano-silicon, and obtain materials with special structures and excellent electrochemical performance.

[0063] The method of this invention is simple and easy to implement, and has excellent results. Furthermore, with the combination of high-energy ball milling and post-treatment, it is possible to unexpectedly obtain materials with excellent electrochemical performance in lithium batteries. Attached Figure Description

[0064] Appendix Figure 1 This is a SEM image of the high-performance lithium-ion battery nano-silicon anode material prepared in Example 1 of the present invention.

[0065] Appendix Figure 2 The image shows the XRD pattern of the high-performance lithium-ion battery nano-silicon anode material prepared in Example 1 of this invention.

[0066] Appendix Figure 3 This is an HRTEM image of the high-performance lithium-ion battery nano-silicon anode material prepared in Example 1 of the present invention.

[0067] Appendix Figure 4 The electrochemical charge-discharge curves of the high-performance lithium-ion battery nano-silicon anode material prepared in Example 1 of this invention and commercial nano-silicon materials are shown.

[0068] Appendix Table 1 is a statistical table of the 0.2C electrochemical performance test results of the embodiments and comparative examples of the present invention.

[0069] From the appendix Figure 1 It can be seen that the high-performance lithium-ion battery nano-silicon anode material prepared in Example 1 of this invention has a uniform morphology and size of about 100 nm, with the larger particles being soft aggregates of small particles; [The text abruptly ends here, likely due to an incomplete translation or missing information.] Figure 2 It can be seen that the nano-silicon anode material obtained after treatment in Example 1 of this invention has Si as its main phase, high crystallinity, and no other impurity phases were introduced during the preparation process. (From the attached...) Figure 3 It can be seen that the high-performance lithium-ion battery nano-silicon anode material prepared in Example 1 of this invention has a rich microstructure, containing both large, regular regions with good crystallinity and areas with abundant defects and unique structures; (The text abruptly ends here, likely due to an incomplete translation or a missing section.) Figure 4 It can be seen that compared with commercial nano-silicon, the high-performance lithium-ion battery nano-silicon anode material prepared in Example 1 of this invention has a more stable charging platform, and the initial coulombic efficiency has been greatly improved, from 79.13% to 92.30%. Detailed Implementation

[0070] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0071] Example 1:

[0072] ① Take 10g of micron-sized silicon raw material and crush it with a crusher. After crushing, pass it through 200 mesh, 400 mesh and 600 mesh sieves respectively. Collect the powder material that has passed through the sieves and disperse it in 400ml of deionized water. Stir for 1 hour and then filter it repeatedly with deionized water until the filtrate is neutral. Take out the obtained filter cake and dry it in an oven at 100℃ to obtain solid material.

[0073] ② Take 5g of the solid material from step ①, grind it finely in an agate mortar, and then put it into a ball mill jar. Weigh 100g of ball mill beads according to a ball-to-material mass ratio of 20:1, add anhydrous ethanol to cover the ball mill beads and material, seal the ball mill jar, adjust the ball mill speed to 300r / min, and mill for 5 hours.

[0074] ③ Collect the ball-milled material obtained in step ② and disperse it in 500ml of deionized water. Stir for 1 hour and then repeatedly filter it with deionized water until the filtrate is neutral. Take out the filter cake and dry it in an oven at 100℃ to obtain nano-silicon powder with a D50 particle size of 200nm.

[0075] ④ The nano-silicon powder obtained in step ③ is sealed in a 310Sφ30*50mm high / low temperature resistant nickel-based stainless steel container in an argon-filled glove box, with a filling capacity of 80%. Then it is taken out and placed in the heating chamber of a tube furnace. Argon atmosphere is introduced into the heating chamber and a stepped high temperature heat treatment is performed. The heat treatment procedure is as follows: first, the temperature is raised from room temperature to 200℃ at a heating rate of 5℃ / min and held for 0.5h; then the temperature is raised to 600℃ at a heating rate of 10℃ / min and held for 1h; finally, the temperature is raised to 800℃ at a heating rate of 2℃ / min and held for 2h.

[0076] ⑤ At the moment the stepped high-temperature heat treatment is completed, open the tube furnace in step ④ and quickly transfer the entire high / low temperature resistant nickel-based stainless steel container (keeping it sealed) into 10L of 10℃ cooling water so that it is fully covered by the cooling water. Stir continuously to accelerate cooling and achieve instantaneous rapid cooling. After 3 hours of standing until the temperature stabilizes, place it in a 100℃ oven for drying. After drying, disassemble the high / low temperature resistant nickel-based stainless steel container and take out the cooled solid material.

[0077] ⑥ The cooled solid material obtained in step ⑤ was dispersed in 100 mL of a 2 mol / L HF solution, stirred at 30 °C for 30 min, and then filtered for solid-liquid separation. The obtained solid was washed with deionized water until neutral, collected, and dried in an oven at 80 °C to obtain the lithium-ion battery nano-silicon anode material. SEM, XRD, and HRTEM results are shown in the figures below. Figure 1 / 2 and 3.

[0078] The obtained nano-silicon anode material has an average particle size of about 100nm, no other impurity phases, is a polycrystalline material, has good crystallinity, and is rich in defects.

[0079] The electrochemical performance of this material was tested using a 2025-type lithium-ion half-cell:

[0080] Using Super P as a conductive agent, sodium alginate as a binder, and deionized water as a solvent, a slurry was prepared and uniformly coated onto copper foil in a mass ratio of active material: conductive agent: binder = 8:1:1. After drying, the slurry was cut into electrode sheets and assembled into a 2025 coin cell using lithium foil as the counter electrode. The electrolyte used was a special electrolyte for silicon-based negative electrode materials (1mol / L LiPF6, EC:DEC = 1:1, 10% FEC), and the separator was made of PP / PE / PP material.

[0081] The half-cell was charged and discharged using a CT2001A battery testing system manufactured by Wuhan Landian Electronics Co., Ltd. The test range was 0.01V to 1.2V, and the test temperature was 25℃.

[0082] After being assembled into a half-cell, the initial coulombic efficiency at 0.2C charge-discharge was 92.30%, and the reversible capacity after 200 cycles was 2102.3 mAh / g.

[0083] Example 2:

[0084] ① Take 10g of micron-sized silicon raw material and crush it with a crusher. After crushing, pass it through 200 mesh, 400 mesh and 600 mesh sieves respectively. Collect the powder material that has passed through the sieves and disperse it in 500ml of deionized water. Stir for 2 hours and then filter it repeatedly with deionized water until the filtrate is neutral. Take out the obtained filter cake and dry it in an oven at 120℃ to obtain solid material.

[0085] ② Take 5g of the solid material from step ①, grind it finely in an agate mortar, and then put it into a ball mill jar. Weigh 150g of ball mill beads according to a ball-to-material mass ratio of 30:1, add anhydrous ethanol to cover the ball mill beads and material, seal the ball mill jar, adjust the ball mill speed to 400r / min, and mill for 3 hours.

[0086] ③ Collect the ball-milled material obtained in step ② and disperse it in 500ml of deionized water. Stir for 1 hour and then repeatedly filter it with deionized water until the filtrate is neutral. Take out the filter cake and dry it in an oven at 100℃ to obtain nano-silicon powder with a D50 particle size of 150nm.

[0087] ④ The nano-silicon powder obtained in step ③ is sealed in an argon-filled glove box in a 310Sφ30*50mm high / low temperature resistant nickel-based stainless steel container with a filling capacity of 80%. Then it is taken out and placed in the heating chamber of a tube furnace. Nitrogen atmosphere is introduced into the heating chamber and a stepped high temperature heat treatment is performed. The heat treatment procedure is as follows: first, the temperature is raised from room temperature to 300℃ at a heating rate of 5℃ / min and held for 0.5h; then the temperature is raised to 600℃ at a heating rate of 10℃ / min and held for 2h; finally, the temperature is raised to 900℃ at a heating rate of 2℃ / min and held for 2h.

[0088] ⑤ At the moment the stepped high-temperature heat treatment is completed, open the tube furnace in step ④ and quickly transfer the entire high / low temperature resistant nickel-based stainless steel container (keeping it sealed) into 3L-196℃ liquid nitrogen, so that it is fully covered by liquid nitrogen and continuously stirred to accelerate cooling, achieving instantaneous rapid cooling. After 3 hours of temperature stabilization, place it in a 100℃ oven for drying. After drying, disassemble the high / low temperature resistant nickel-based stainless steel container and take out the cooled solid material.

[0089] ⑥ The cooled solid material obtained in step ⑤ is dispersed in 100 mL of HF solution with a concentration of 1 mol / L. After stirring at 30 °C for 20 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected and dried in an oven at 100 °C to obtain the lithium-ion battery nano-silicon anode material.

[0090] The obtained nano-silicon anode material has a particle size of about 50-150 nm, no other impurity phases, good crystallinity, and abundant defects. After being assembled into a half-cell according to the method of Example 1, the initial coulombic efficiency at 0.2C charge and discharge is 92.25%, and the reversible capacity after 200 cycles is 2036.5 mAh / g.

[0091] Example 3:

[0092] ① Take 10g of micron-sized silicon raw material and crush it with a crusher. After crushing, pass it through 200 mesh, 400 mesh and 600 mesh sieves respectively. Collect the powder material that has passed through the sieves and disperse it in 500ml of deionized water. Stir for 1 hour and then filter it repeatedly with deionized water until the filtrate is neutral. Take out the obtained filter cake and dry it in an oven at 100℃ to obtain solid material.

[0093] ② Take 5g of the solid material from step ①, grind it finely in an agate mortar, and then put it into a ball mill jar. Weigh 200g of ball mill beads according to a ball-to-material mass ratio of 40:1, add anhydrous ethanol to cover the ball mill beads and material, seal the ball mill jar, adjust the ball mill speed to 200r / min, and mill for 2 hours.

[0094] ③ Collect the ball-milled material obtained in step ② and disperse it in 500ml of deionized water. Stir for 1 hour and then repeatedly filter it with deionized water until the filtrate is neutral. Take out the filter cake and dry it in an oven at 100℃ to obtain nano-silicon powder with a D50 particle size of 180nm.

[0095] ④ The nano-silicon powder obtained in step ③ is sealed in a 310Sφ50*50mm high / low temperature resistant nickel-based stainless steel container in an argon-filled glove box, with a filling capacity of 50%. Then it is taken out and placed in the heating chamber of a tube furnace. Nitrogen atmosphere is introduced into the heating chamber and a stepped high temperature heat treatment is performed. The heat treatment procedure is as follows: first, the temperature is raised from room temperature to 200℃ at a heating rate of 5℃ / min and held for 1 hour; then the temperature is raised to 600℃ at a heating rate of 10℃ / min and held for 2 hours; finally, the temperature is raised to 1000℃ at a heating rate of 2℃ / min and held for 2 hours.

[0096] ⑤ At the moment the stepped high-temperature heat treatment is completed, open the tube furnace in step ④ and quickly transfer the entire high / low temperature resistant nickel-based stainless steel container (keeping it sealed) into 5L of 10℃ polyethylene glycol, so that it is fully coated with polyethylene glycol, and stir continuously to accelerate cooling and achieve instantaneous rapid cooling. After 3 hours of temperature stabilization, place it in a 100℃ oven for drying. After drying, disassemble the high / low temperature resistant nickel-based stainless steel container and take out the cooled solid material.

[0097] ⑥ The cooled solid material obtained in step ⑤ is dispersed in 100 mL of HF solution with a concentration of 3 mol / L. After stirring at 40 °C for 40 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected and dried in an oven at 100 °C to obtain the lithium-ion battery nano-silicon anode material.

[0098] The obtained nano-silicon anode material has a particle size of about 50-100 nm, no other impurity phases, and good crystallinity. After being assembled into a half-cell according to the method in Example 1, the initial coulombic efficiency at 0.2C charge and discharge is 90.67%, and the reversible capacity after 200 cycles is 1901.7 mAh / g.

[0099] Example 4:

[0100] ① Take 10g of micron-sized silicon raw material and crush it with a crusher. After crushing, pass it through 200 mesh, 400 mesh and 600 mesh sieves respectively. Collect the powder material that has passed through the sieves and disperse it in 500ml of deionized water. Stir for 1 hour and then filter it repeatedly with deionized water until the filtrate is neutral. Take out the obtained filter cake and dry it in an oven at 100℃ to obtain solid material.

[0101] ② Take 5g of the solid material from step ①, grind it finely in an agate mortar, and then put it into a ball mill jar. Weigh 100g of ball milling beads according to a ball-to-material mass ratio of 20:1, add deionized water to cover the ball milling beads and the material, seal the ball mill jar, adjust the ball mill speed to 500r / min, and mill for 6 hours.

[0102] ③ Collect the ball-milled material obtained in step ② and disperse it in 500ml of deionized water. Stir for 1 hour and then repeatedly filter it with deionized water until the filtrate is neutral. Take out the filter cake and dry it in an oven at 100℃ to obtain nano-silicon powder with a D50 particle size of 300nm.

[0103] ④ The nano-silicon powder obtained in step ③ is sealed in an argon-filled glove box into a 310Sφ25*50mm high / low temperature resistant nickel-based stainless steel container with a filling capacity of 90%. Then it is taken out and placed in the heating chamber of a tube furnace. A carbon dioxide atmosphere is introduced into the heating chamber and a step-high temperature heat treatment is performed. The heat treatment procedure is as follows: first, the temperature is raised from room temperature to 200℃ at a heating rate of 5℃ / min and held for 0.5h; then, the temperature is raised to 600℃ at a heating rate of 10℃ / min and held for 1h; finally, the temperature is raised to 1200℃ at a heating rate of 5℃ / min and held for 4h.

[0104] ⑤ At the moment the stepped high-temperature heat treatment is completed, open the tube furnace in step ④ and quickly transfer the entire high / low temperature resistant nickel-based stainless steel container (keeping it sealed) into 4kg of dry ice at -78.5℃, so that it is fully wrapped by the dry ice, and stir continuously to accelerate cooling and achieve instantaneous rapid cooling. After 3 hours of temperature stabilization, place it in a 100℃ oven for drying. After drying, disassemble the high / low temperature resistant nickel-based stainless steel container and take out the cooled solid material.

[0105] ⑥ The cooled solid material obtained in step ⑤ is dispersed in 200 mL of HF solution with a concentration of 5 mol / L. After stirring at 40 °C for 60 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected and dried in an oven at 100 °C to obtain the lithium-ion battery nano-silicon anode material.

[0106] The obtained nano-silicon anode material has a particle size of about 150 nm, no other impurity phases, and good crystallinity. After being assembled into a half-cell according to the method in Example 1, the initial coulombic efficiency at 0.2C charge and discharge is 90.74%, and the reversible capacity after 200 cycles is 1935.0 mAh / g.

[0107] Example 5:

[0108] ① Take 10g of micron-sized silicon raw material and crush it with a crusher. After crushing, pass it through 200 mesh, 400 mesh and 600 mesh sieves respectively. Collect the powder material that has passed through the sieves and disperse it in 400ml of deionized water. Stir for 1 hour and then filter it repeatedly with deionized water until the filtrate is neutral. Take out the obtained filter cake and dry it in an oven at 100℃ to obtain solid material.

[0109] ② Take 5g of the solid material from step ①, grind it finely in an agate mortar, and then put it into a ball mill jar. Weigh 200g of ball mill beads according to the ball-to-material mass ratio of 40:1, add anhydrous ethanol to cover the ball mill beads and material, seal the ball mill jar, adjust the ball mill speed to 500r / min, and mill for 5h.

[0110] ③ Collect the ball-milled material obtained in step ② and disperse it in 500ml of deionized water. Stir for 1 hour and then repeatedly filter it with deionized water until the filtrate is neutral. Take out the filter cake and dry it in an oven at 100℃ to obtain nano-silicon powder with a D50 particle size of 100nm.

[0111] ④ The nano-silicon powder obtained in step ③ is sealed in an argon-filled glove box into a US366φ30*50mm high / low temperature molybdenum alloy container with a filling capacity of 70%. Then it is taken out and placed in the heating chamber of a tube furnace. Argon atmosphere is introduced into the heating chamber and a stepped high temperature heat treatment is performed. The heat treatment procedure is as follows: first, the temperature is raised from room temperature to 200℃ at a heating rate of 5℃ / min and held for 0.5h; then the temperature is raised to 600℃ at a heating rate of 10℃ / min and held for 1h; finally, the temperature is raised to 1000℃ at a heating rate of 2℃ / min and held for 2h.

[0112] ⑤ At the moment the stepped high-temperature heat treatment is completed, open the tube furnace in step ④ and quickly transfer the entire high / low temperature resistant molybdenum alloy container (keeping it sealed) into a large amount of 10L 10℃ cooling water so that it is fully covered by the cooling water. Stir continuously to accelerate cooling and achieve instantaneous rapid cooling. After 3 hours of standing until the temperature stabilizes, place it in a 100℃ oven for drying. After drying, disassemble the high / low temperature resistant molybdenum alloy container and take out the cooled solid material.

[0113] ⑥ The cooled solid material obtained in step ⑤ is dispersed in 100 mL of HF solution with a concentration of 2 mol / L. After stirring at 30 °C for 30 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected and dried in an oven at 80 °C to obtain the lithium-ion battery nano-silicon anode material.

[0114] ⑦ The lithium-ion battery nano-silicon anode material obtained in step ⑥ is placed in a mixer at a mass ratio of 1:1 and run at a speed of 300 r / min for 10 hours to ensure that the two materials are completely and uniformly combined, thereby obtaining a high-performance lithium-ion battery nano-silicon / carbon composite anode material.

[0115] The obtained high-performance lithium-ion battery nano-silicon / carbon composite anode material has a nano-silicon particle size of about 100nm and a graphite size of about 10μm. The nano-silicon is attached to the graphite surface and the composite is uniform. After being assembled into a half cell according to the method of Example 1, the first coulombic efficiency of 0.2C charge and discharge is 95.65%, and the reversible capacity after 200 cycles is 1525.8mAh / g.

[0116] Example 6:

[0117] ① Take 10g of micron-sized silicon raw material and crush it with a crusher. After crushing, pass it through 200 mesh, 400 mesh and 600 mesh sieves respectively. Collect the powder material that has passed through the sieves and disperse it in 400ml of deionized water. Stir for 1 hour and then filter it repeatedly with deionized water until the filtrate is neutral. Take out the obtained filter cake and dry it in an oven at 100℃ to obtain solid material.

[0118] ② Take 5g of the solid material from step ①, grind it finely in an agate mortar, and then put it into a ball mill jar. Weigh 200g of ball mill beads according to the ball-to-material mass ratio of 40:1, add anhydrous ethanol to cover the ball mill beads and material, seal the ball mill jar, adjust the ball mill speed to 500r / min, and mill for 5h.

[0119] ③ Collect the ball-milled material obtained in step ② and disperse it in 500ml of deionized water. Stir for 1 hour and then repeatedly filter it with deionized water until the filtrate is neutral. Take out the filter cake and dry it in an oven at 100℃ to obtain nano-silicon powder with a D50 particle size of 100nm.

[0120] ④ The nano-silicon powder obtained in step ③ is sealed in an argon-filled glove box into a US366φ40*50mm high / low temperature resistant molybdenum alloy container with a filling capacity of 60%. Then, it is taken out and placed in the heating chamber of a tube furnace. Argon atmosphere is introduced into the heating chamber and a stepped high temperature heat treatment is performed. The heat treatment procedure is as follows: first, the temperature is increased from room temperature to 200℃ at a heating rate of 5℃ / min and held for 0.5h; then, the temperature is increased to 400℃ at a heating rate of 5℃ / min and held for 1h; then, the temperature is increased to 700℃ at a heating rate of 10℃ / min and held for 2h; finally, the temperature is increased to 1000℃ at a heating rate of 2℃ / min and held for 2h.

[0121] ⑤ At the moment the stepped high-temperature heat treatment is completed, open the tube furnace in step ④ and quickly transfer the entire high / low temperature resistant molybdenum alloy container (keeping it sealed) into a large amount of 3L-196℃ liquid nitrogen, so that it is fully covered by liquid nitrogen and continuously stirred to accelerate cooling, achieving instantaneous rapid cooling. After 3 hours of temperature stabilization, place it in a 100℃ oven for drying. After drying, disassemble the high / low temperature resistant molybdenum alloy container and take out the cooled solid material.

[0122] ⑥ The cooled solid material obtained in step ⑤ is dispersed in 100 mL of HF solution with a concentration of 2 mol / L. After stirring at 30 °C for 30 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected and dried in an oven at 80 °C to obtain the lithium-ion battery nano-silicon anode material.

[0123] The obtained high-performance lithium-ion battery nano-silicon anode material has a nano-silicon particle size of about 100nm. After being assembled into a half-cell according to the method in Example 1, the first coulombic efficiency of 0.2C charge and discharge is 93.52%, and the reversible capacity after 200 cycles is 2074.6mAh / g.

[0124] Comparative Example 1:

[0125] Compared with Example 1, the only difference is that steps ② and ③ are omitted. The difference is as follows:

[0126] Take ① to obtain solid material, omit the nano-sizing treatments ② and ③, and directly carry out ④ and subsequent heat treatment and quenching treatment, etc., with the same operation and conditions as in Example 1.

[0127] The obtained silicon anode material has a particle size of about 1 to 5 μm. When assembled into a half cell according to the method in Example 1, the initial coulombic efficiency at 0.2C charge and discharge is about 80%, and the reversible capacity after 200 cycles is 235.5 mAh / g.

[0128] Comparative Example 2:

[0129] Compared to Example 1, the main difference is that a protective atmosphere was not used in the high-temperature heat treatment process. The specific operation is as follows:

[0130] ① Take 10g of micron-sized silicon raw material and process it according to the same method as in Example 1 to obtain nano-silicon powder;

[0131] ② The nano-silicon powder obtained in step ① is sealed in a 310Sφ30*50mm high / low temperature resistant nickel-based stainless steel container in an argon-filled glove box, with a filling capacity of 80%. Then it is taken out and placed in the heating chamber of a tube furnace. An air atmosphere is introduced into the heating chamber and a stepped high temperature heat treatment is performed. The heat treatment procedure is as follows: first, the temperature is raised from room temperature to 200℃ at a heating rate of 5℃ / min and held for 0.5h; then, the temperature is raised to 600℃ at a heating rate of 10℃ / min and held for 1h; finally, the temperature is raised to 800℃ at a heating rate of 2℃ / min and held for 2h.

[0132] ③ After completing the stepped high-temperature heat treatment, the subsequent operations were carried out in the same manner as in Example 1 to finally obtain the material;

[0133] The obtained material was assembled into a half-cell according to the method of Example 1. The first coulombic efficiency at 0.2C charge and discharge was less than 50%, and the reversible capacity after 200 cycles was 157.6 mAh / g.

[0134] Comparative Example 3:

[0135] Compared to Example 1, the main difference is that no high-temperature heat treatment was performed; instead, liquid nitrogen cooling was carried out directly at room temperature. The difference lies in the following steps:

[0136] ① Take 10g of micron-sized silicon raw material and process it according to the same method as in Example 1 to obtain nano-silicon powder;

[0137] ② The nano-silicon powder obtained in step ① is sealed in an argon-filled glove box in a 310Sφ30*50mm high / low temperature resistant nickel-based stainless steel container with a filling capacity of 80%. Then, without heat treatment, the entire high / low temperature resistant nickel-based stainless steel container is directly transferred to 3L-196℃ liquid nitrogen to fully encapsulate it. The container is continuously stirred to accelerate cooling and achieve instantaneous rapid cooling. After 3 hours of temperature stabilization, it is placed in a 100℃ oven for drying. After drying, the high / low temperature resistant nickel-based stainless steel container is disassembled and the cooled solid material is removed.

[0138] ③ The cooled solid material obtained in step ② is dispersed in 100 mL of HF solution with a concentration of 2 mol / L. After stirring at 30 °C for 30 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected. It is then dried in an oven at 80 °C to obtain the material.

[0139] The obtained material has a particle size of about 100 nm and slightly poor crystallinity. When assembled into a half-cell according to the method in Example 1, the initial coulombic efficiency at 0.2C charge and discharge is about 70%, and the reversible capacity after 200 cycles is 678.2 mAh / g.

[0140] Comparative Example 4:

[0141] Compared to Example 1, the only difference is that the nano-silicon powder was not subjected to the secondary heat treatment described above. Specifically:

[0142] ① Take 10g of micron-sized silicon raw material and process it according to the same method as in Example 1 to obtain nano-silicon powder;

[0143] ② The nano-silicon powder obtained in step ① is placed in an alumina crucible and then subjected to step-high temperature heat treatment in a tube furnace under a nitrogen atmosphere. The heat treatment procedure is as follows: first, the temperature is increased from room temperature to 200℃ at a heating rate of 5℃ / min and held for 0.5h; then, the temperature is increased to 600℃ at a heating rate of 10℃ / min and held for 1h; finally, the temperature is increased to 800℃ at a heating rate of 2℃ / min and held for 2h.

[0144] ③ At the moment the stepped high-temperature heat treatment is completed, the tube furnace in step ② is opened and the product of the entire alumina crucible is quickly transferred to 3L-196℃ liquid nitrogen, so that it is fully covered by liquid nitrogen, and the mixture is continuously stirred to accelerate cooling and achieve instantaneous rapid cooling. After 3 hours of temperature stabilization, it is placed in a 100℃ oven for drying. After drying, the cooled solid material is obtained.

[0145] ④ The cooled solid material obtained in step ③ is dispersed in 100 mL of HF solution with a concentration of 2 mol / L. After stirring at 30 °C for 30 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected. It is then dried in an oven at 80 °C to obtain the material.

[0146] The obtained material was assembled into a half-cell according to the method of Example 1. The first coulombic efficiency at 0.2C charge and discharge was less than 50%, and the reversible capacity after 200 cycles was 384.5 mAh / g.

[0147] Comparative Example 5:

[0148] Compared to Example 1, the only difference is that instead of instantaneous extreme cooling, furnace cooling is used. For example, in step ⑤, after the heat treatment, the high / low temperature resistant nickel-based stainless steel container containing nano-silicon powder is allowed to cool in the furnace, and then the heat-treated solid material is obtained. Other processing steps are the same as in Example 1.

[0149] The obtained material was assembled into a half-cell according to the method of Example 1. The initial coulombic efficiency at 0.2C charge and discharge was about 70%, and the reversible capacity after 200 cycles was 549.3 mAh / g.

[0150] Comparative Example 6:

[0151] Compared with Example 1, the only difference is the absence of step ⑥; all other operations and processes are the same as in Example 1.

[0152] The obtained material was assembled into a half-cell according to the method of Example 1. The first coulombic efficiency at 0.2C charge and discharge was less than 50%, and the reversible capacity after 200 cycles was 368.2 mAh / g.

[0153] Comparative Example 7:

[0154] Compared to Example 1, the only difference is that secondary conduction was not performed directly on the nano-silicon. The steps are as follows: the micron-sized raw material first undergoes high-temperature heat treatment, cooling process, and post-treatment, and finally undergoes high-energy ball milling nano-sizing treatment, specifically:

[0155] ① The solid material obtained is the same as in Example 1;

[0156] ② Take 5g of the solid material from step ① and seal it in a 310Sφ30*50mm high / low temperature resistant nickel-based stainless steel container in an argon-filled glove box, filling the container to 80% capacity. Then take it out and place it in the heating chamber of a tube furnace. Introduce argon atmosphere into the heating chamber and perform step high temperature heat treatment. The heat treatment procedure is as follows: first, heat the material from room temperature to 200℃ at a heating rate of 5℃ / min and hold for 0.5h; then heat the material to 600℃ at a heating rate of 10℃ / min and hold for 1h; finally, heat the material to 800℃ at a heating rate of 2℃ / min and hold for 2h.

[0157] ③ At the moment the stepped high-temperature heat treatment is completed, open the tube furnace in step ② and quickly transfer the entire high / low temperature resistant nickel-based stainless steel container into 10L of 10℃ cooling water so that it is fully covered by the cooling water. Stir continuously to accelerate cooling and achieve instantaneous rapid cooling. After 3 hours of temperature stabilization, place it in a 100℃ oven for drying. After drying, disassemble the high / low temperature resistant nickel-based stainless steel container and take out the cooled solid material.

[0158] ④ The cooled solid material obtained in step ③ is dispersed in 100 mL of HF solution with a concentration of 2 mol / L. After stirring at 30 °C for 30 min, the solid is separated by filtration. The obtained solid is washed with deionized water until neutral and then collected. It is then dried in an oven at 80 °C to obtain the post-processed material.

[0159] ⑤ Grind the post-processed material obtained in step ④ into an agate mortar and then put it into a ball mill jar. Weigh the ball mill beads according to the ball-to-material mass ratio of 20:1, add anhydrous ethanol to cover the ball mill beads and material, seal the ball mill jar, adjust the ball mill speed to 300 r / min, and ball mill for 5 hours.

[0160] ⑥ Collect the ball-milled material obtained in step ⑤ and disperse it in 500 ml of deionized water. Stir for 1 hour and then repeatedly filter it with deionized water until the filtrate is neutral. Take out the filter cake and dry it in an oven at 100°C to obtain the material.

[0161] The obtained material was assembled into a half-cell according to the method of Example 1. The first coulombic efficiency at 0.2C charge and discharge was less than 50%, and the reversible capacity after 200 cycles was 605.9 mAh / g.

[0162] Comparative Example 8:

[0163] Compared with Example 1, the only difference is that the heat treatment and rapid cooling treatment are omitted, and the nano-silicon powder from step ③ is directly processed in step ⑥.

[0164] The obtained material was assembled into a half-cell according to the method of Example 1. The initial coulombic efficiency at 0.2C charge and discharge was about 72%, and the reversible capacity after 200 cycles was 476.3 mAh / g.

[0165] Comparative Example 9:

[0166] Compared to Example 1, the only difference is that in step ⑤, the gradient heat treatment with two-stage conduction is not performed. For example, the step is as follows:

[0167] ① Take 10g of micron-sized silicon raw material and process it using the same method as in Example 1 to obtain nano-silicon powder;

[0168] ② The nano-silicon powder obtained in step ① is sealed in an argon-filled glove box in a 310Sφ30*50mm high / low temperature resistant nickel-based stainless steel container with a filling capacity of 80%. Then it is taken out and placed in the heating chamber of a tube furnace. Argon atmosphere is introduced into the heating chamber and conventional high-temperature heat treatment is performed. The heat treatment procedure is as follows: the temperature is increased from room temperature to 800℃ at a heating rate of 5℃ / min and held for 2 hours.

[0169] ③ After completing the conventional high-temperature heat treatment, subsequent operations were carried out according to the processing method of Example 1 to finally obtain the silicon anode material for lithium-ion batteries;

[0170] The obtained material was assembled into a half-cell according to the method of Example 1. The initial coulombic efficiency at 0.2C charge and discharge was about 70%, and the reversible capacity after 200 cycles was 968.3 mAh / g.

[0171] The results of each case are shown in Table 1.

[0172] Table 1. Statistical table of electrochemical performance test results at 0.2C for the examples and comparative examples.

[0173]

[0174]

[0175] Through examples and comparative examples, it is shown that high-energy ball milling nano-sizing is beneficial for reducing and unifying the particle size of silicon materials, regulating the morphology of nano-silicon particles, and improving the electrochemical reactivity of silicon materials. This helps alleviate the volume effect during charge and discharge processes and improves the cycle performance of the material. The presence of a high / low temperature resistant alloy sealing container effectively protects the nano-silicon powder, preventing it from being damaged during subsequent processing. It also organically couples high-temperature heat treatment and extreme cold treatment, achieving a "1+1>2" effect. The stepped high-temperature heat treatment process can improve the crystallinity of the material, change the microstructure of the material, and generate abundant defects. At the same time, the presence of a protective atmosphere ensures the reliable transformation of the material, thereby improving the electrochemical performance of the final material, and significantly improving the coulombic efficiency and cycle performance. The instantaneous extreme cooling process helps stabilize the material's performance and structure, allowing the material's characteristics to be fully utilized, while the post-processing process further optimizes the material's performance. Ultimately, the cooperation and synergistic effect of each process and preparation parameter are necessary to fully realize the advantages of this invention and obtain high-performance lithium-ion battery nano-silicon anode materials.

Claims

1. A method for thermal-cold sealing coupling treatment of nano-silicon, characterized in that, Nano-silicon is filled and sealed in a heat-conducting container, and then the heat-conducting container is subjected to a secondary heat transfer gradient heat treatment in an inert gas atmosphere. It is then placed in a cooling medium system for rapid cooling treatment, and finally subjected to post-treatment, washing and drying treatment to obtain the treated nano-silicon. The gradient heat treatment process includes 2 to 5 insulation platforms, wherein the temperature of the initial insulation platform is 200 to 300°C, and the temperature of the final insulation platform is 800 to 1200°C. The wall material of the heat-conducting container has a melting point temperature greater than or equal to 1400℃ and a thermal conductivity greater than or equal to 100W / m·K.

2. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The particle size of nano-silicon is less than or equal to 500 nm.

3. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 2, characterized in that, The particle size of nano-silicon is less than or equal to 300 nm.

4. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 3, characterized in that, The particle size of nano-silicon is 50~300nm.

5. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 3, characterized in that, The particle size of nano-silicon is 50~100nm.

6. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The nano-silicon is obtained by ball milling elemental silicon.

7. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 6, characterized in that, The silicon material is in the form of particles or blocks with a size of micrometers or larger.

8. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 6, characterized in that, The silicon material is at least one of monocrystalline silicon, polycrystalline silicon, or amorphous silicon.

9. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 6, characterized in that, The ball milling can be either dry or wet.

10. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 9, characterized in that, The ball milling medium is at least one of an inert gas and a liquid, wherein the inert gas is at least one of argon, nitrogen, and helium; the liquid is at least one of anhydrous ethanol, ultrapure water, polyethylene glycol, and glycerol; the ball-to-material ratio in the ball milling process is 10~60:1; the ball milling speed is 100~600 r / min; and the ball milling time is 2~10 h.

11. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The wall material of the heat-conducting container does not undergo brittle fracture at -200℃.

12. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The wall material of the heat-conducting container is an alloy material.

13. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 12, characterized in that, The wall material of the heat-conducting container is one of stainless steel, aluminum alloy, copper alloy, molybdenum alloy, tungsten alloy, niobium alloy, and nickel alloy.

14. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The nano-silicon is filled into the heat-conducting container chamber under a protective atmosphere and then sealed.

15. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 14, characterized in that, The protective atmosphere is at least one of an inert gas, carbon dioxide, and hydrogen.

16. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 14, characterized in that, The packing capacity of nano-silicon is greater than or equal to 50%.

17. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The gradient heat treatment process includes three heat preservation processes. The first heat preservation temperature is 200~300℃, the second heat preservation temperature is 500~650℃, and the third heat preservation temperature is 800~1200℃.

18. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 17, characterized in that, The heating rate to the first insulation temperature is 4~6℃ / min; the heating rate from the first insulation temperature to the second insulation temperature is 10~15℃ / min; and the heating rate from the second insulation temperature to the third insulation temperature is 1~3℃ / min.

19. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 17, characterized in that, The first insulation period is 0.5 to 1 hour; the second insulation period is 1 to 2 hours; and the third insulation period is 2 to 4 hours.

20. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, After gradient heat treatment, the heat-conducting container, which is kept in a sealed state, is directly placed in a cooling medium for rapid cooling.

21. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The cooling medium can be a liquid cooling medium or a gas cooling medium.

22. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The cooling medium is one or more of anhydrous ethanol, polyethylene glycol, deionized water, liquid nitrogen, dry ice, air, argon, and nitrogen.

23. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The temperature difference between the heat-conducting container and the initial cooling medium is greater than or equal to 800°C.

24. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, The post-treatment is acid treatment, alkali treatment, or a mixture of acid treatment and alkali treatment in any order.

25. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 24, characterized in that, The acid solution is an aqueous solution containing HF.

26. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 24, characterized in that, The alkaline solution is an aqueous solution containing dissolved alkali metal hydroxides.

27. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 24, characterized in that, The temperature for post-processing is 10~60℃.

28. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, Washing is done with water.

29. The nano-silicon thermal-cold sealing coupling treatment method as described in claim 1, characterized in that, Wash with water until the pH of the filtrate is 6.5-7.

5.

30. A treated nano-silicon prepared by the preparation method according to any one of claims 1 to 29.

31. The nano-silicon as described in claim 30, characterized in that, The prepared treated nano-silicon has defect structures and / or twin phases.

32. An application of the treated nano-silicon prepared by the method according to any one of claims 1 to 29, characterized in that, It is used to make batteries.

33. The application as described in claim 32, characterized in that, It is used to prepare the negative electrode of the battery.

34. The application as described in claim 32, characterized in that, The battery in question is a lithium-ion battery.

35. A lithium-ion battery, characterized in that, It includes treated nano-silicon prepared by the preparation method according to any one of claims 1 to 29.

36. The lithium-ion battery as described in claim 35, characterized in that, Its negative electrode contains a negative electrode material comprising the treated nano-silicon.

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