Preparation method of modified nano silicon powder for silicon-carbon negative electrode

Abstract

The invention discloses a preparation method of modified nano silicon powder for a silicon-carbon negative electrode, which is characterized in that the nano silicon powder for the silicon-carbon negative electrode is prepared from industrial coarse silicon or photovoltaic silicon waste as a raw material through the technological processes of acid pickling and drying, high-temperature roasting, physical grinding, pre-lithiation, high-temperature coating and the like. The preparation method of the nano silicon powder for the silicon-carbon negative electrode has the advantages of low cost, simple process, uniform granularity, high purity, large-scale preparation and the like, and a lithium film forming agent is added in the grinding process, so that the problem of lithium consumption in the film reconstruction process of a solid electrolyte layer (SEI) on the surface of a silicon particle can be effectively solved; and the soft carbon material is added in the high-temperature coating process, so that the problem of expansion and pulverization of silicon in the lithium intercalation / deintercalation process can be effectively inhibited, and the preparation method has a good industrialization prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium - ion batteries, and particularly to a preparation method of modified nano - silicon powder for silicon - carbon anodes. Background Art

[0002] Currently, the commercially available graphite anode materials in lithium - ion batteries can no longer meet the demand for high - capacity batteries due to their capacity limitations. Therefore, it is necessary to find some new high - capacity and low - cost lithium - ion battery anode materials. Among them, silicon materials have become a research hotspot due to their high theoretical specific capacity (pure silicon is 4200 mAh / g) and low cost. However, silicon materials will undergo a large volume expansion (up to 300%) during charge and discharge processes, causing the electrode materials to powder and even fall off, resulting in poor cycle performance of the battery. The commonly used solution is to nano - size and surface - modify silicon to reduce the impact of expansion on battery life and cycle performance.

[0003] Currently, the main methods for preparing micron - sized silicon in the market are the laser method and the silane pyrolysis method. The silicon prepared by the laser method is usually nano - silicon, and its particle size can be as low as 30 nm. The price of 30 - nm silicon in the market is as high as 3 million yuan per ton, and the equipment used is very expensive and cannot be prepared on a large scale, which greatly limits the practical application of silicon materials in the battery field, such as the disclosed patent 2023112293318; for the other method of preparing nano - silicon by silane pyrolysis, such as the disclosed patent 2006100313232, the minimum particle size is 80 nm, and its price is also as high as 2 million yuan per ton. Although the silicon prepared by this method has high purity, this method has relatively harsh production conditions, and the SiH4 and H2 generated during the production process are flammable and explosive, and the entire system must be isolated from oxygen and cannot be in contact with the outside world. Therefore, this method also has great potential safety hazards. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of modified nano - silicon powder for silicon - carbon anodes, aiming to solve the problems that the existing processes for preparing nano - silicon are complex, the raw material cost is too high, and it is difficult to achieve large - scale production.

[0005] The present invention provides a preparation method of modified nano - silicon powder for silicon - carbon anodes, and the preparation method includes the following steps: Step 1: After crushing industrial crude silicon or photovoltaic silicon waste into millimeter - sized small particles, an acidic solution is added thereto, stirred and washed, and after filtration, the crude silicon is dried to obtain crude silicon A for standby; Step 2: Take out the dried crude silicon A and calcine it in a reducing atmosphere to obtain crude silicon B; Step 3: Mix and stir the crude silicon B with a grinding aid and a dispersant, add grinding media, and grind thoroughly under an inert atmosphere to prepare a nano-silicon slurry; Step 4: Add a lithium-containing reagent to the above nano-silicon slurry, stir and disperse it to form a lithium-containing film on the surface of the silicon; Step 5: Dry the above nano-silicon slurry to prepare nano-silicon powder; Step 6: Thoroughly mix the above nano-silicon powder with a soft carbon material and perform high-temperature coating to prepare modified nano-silicon powder.

[0006] Further improvement lies in: in Step 1, the particle size of the industrial crude silicon or photovoltaic waste silicon material after crushing is 1 mm - 5 mm; the acidic solution is one or more of dilute hydrochloric acid, dilute sulfuric acid, acetic acid, and dilute nitric acid; the drying temperature is 50 - 90 °C, preferably 70 °C.

[0007] Further improvement lies in: in Step 1, the reducing atmosphere is one of hydrogen, carbon monoxide, nitrogen-hydrogen mixture, and carbon monoxide mixture; the roasting temperature is 400 - 800 °C, preferably 500 °C.

[0008] Further improvement lies in: in Step 3, the grinding aid is one or more of methanol, ethanol, ethylene glycol, and methyl pentanol, and the dispersant is one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, and ethylenediaminetetraacetic acid; the grinding media is a mixture of one or more specifications of agate balls and zirconia balls; the inert atmosphere is one of nitrogen, argon, and neon.

[0009] Further improvement lies in: in Step 4, the lithium-containing reagent is one or more of lithium sulfide, lithium oxide, and lithium-silicon compounds.

[0010] Further improvement lies in: in Step 5, the drying method is one of spray drying, flash drying, and rotary evaporation.

[0011] Further improvement lies in: in Step 6, the soft carbon material is one or more of resin, asphalt, and sucrose; the high-temperature coating temperature is between 500 - 1100 °C, preferably 700 °C.

[0012] The beneficial effects of the present invention are as follows: The preparation method of the present invention uses inexpensive industrial crude silicon or photovoltaic silicon waste as raw materials, and prepares modified nano-silicon powder meeting the requirements of silicon-carbon anode materials through processes such as pickling and drying, high-temperature roasting, physical grinding, prelithiation, and high-temperature coating. It has the advantages of low cost, simple process, uniform particle size, high purity, and scalable preparation. Moreover, a prelithiation reagent is added during the grinding process, which can effectively solve the problem of lithium consumption during the reconstruction of the solid electrolyte interface (SEI) film on the surface of silicon particles. Adding soft carbon materials during the high-temperature coating process can effectively inhibit the swelling and pulverization of silicon during the lithium deintercalation / insertion process, and has good industrialization prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flowchart for preparing the modified nano-silicon material prepared by the present invention. SPECIFIC EMBODIMENTS

[0014] To deepen the understanding of the present invention, the following will further elaborate on the present invention in combination with embodiments. The embodiments are only used to explain the present invention and do not constitute a limitation to the protection scope of the present invention. Embodiment

[0015] Weigh 1000 g of industrial crude silicon, put it into a crusher for multiple crushing, sieve it through a 50-mesh sieve, then put it into a stirring tank, add 2 L of dilute hydrochloric acid solution with a concentration of 1 mol / L into the tank, stir at 100 r / min for 2 h, filter and wash it with deionized water, and put the obtained filter residue into a vacuum drying oven. Set the temperature to 70 °C and dry for 12 h to obtain crude silicon A; weigh 200 g of crude silicon A and place it in a square crucible. Roast it in a high-temperature roasting furnace under a nitrogen-hydrogen mixed atmosphere for 3 h to obtain crude silicon B; after cooling, take out crude silicon B, place it in a stirring tank, add 2 L of ethylene glycol and 2 g of sodium dodecylbenzenesulfonate respectively, stir evenly, then add 2 Kg of zirconia beads with a particle size of 0.1 mm into a grinder, turn on nitrogen protection, and grind at a speed of 1500 r / min for 5 h to obtain nano-silicon slurry; add 10 ml of lithium sulfide reagent into the slurry, turn on mechanical stirring for 30 min, take out the slurry for spray drying, set the inlet air temperature to 90 °C and the outlet air temperature to 60 °C to obtain pretreated nano-silicon powder; weigh 50 g of the pretreated nano-silicon powder and mix it evenly with 50 g of asphalt powder, put it into a coating machine, set the coating temperature to 600 °C, and perform high-temperature coating under a nitrogen atmosphere for 3 h. After cooling, take it out to prepare the modified nano-silicon material. Embodiment

[0016] Weigh 1000 g of photovoltaic single-crystalline silicon waste and put it into a crusher for multiple crushing. After sieving through a 50-mesh sieve, put it into a stirring tank. Add 2 L of dilute hydrochloric acid solution with a concentration of 1 mol / L into the tank, stir at 100 r / min for 2 h, filter and wash with deionized water. Put the obtained filter residue into a vacuum drying oven, set the temperature at 70 °C, and dry for 12 h to obtain crude silicon A. Weigh 200 g of crude silicon A and place it in a square crucible. Roast it in a high-temperature roasting furnace under a nitrogen-hydrogen mixed atmosphere for 3 h to obtain crude silicon B. After cooling, take out crude silicon B, place it in a stirring tank, add 2 L of ethylene glycol and 2 g of sodium dodecylbenzenesulfonate respectively. After stirring evenly, add 2 Kg of zirconia beads with a particle size of 0.1 mm into a grinding machine, turn on nitrogen protection, and grind at a speed of 1500 r / min for 5 h to obtain nano-silicon slurry. Add 10 ml of lithium sulfide reagent into the slurry, turn on mechanical stirring for 30 min, take out the slurry for spray drying, set the inlet air temperature at 90 °C and the outlet air temperature at 60 °C to obtain pre-treated nano-silicon powder. Weigh 50 g of the pre-treated nano-silicon powder and mix it evenly with 50 g of asphalt powder, put it into a coating machine, set the coating temperature at 600 °C, and perform high-temperature coating under a nitrogen atmosphere for 3 h. After cooling, take it out to prepare a modified nano-silicon material. Example

[0017] Weigh 1000 g of industrial crude silicon and put it into a crusher for multiple crushing. After sieving through a 50-mesh sieve, put it into a stirring tank. Add 2 L of dilute hydrochloric acid solution with a concentration of 1 mol / L into the tank, stir at 100 r / min for 2 h, filter and wash with deionized water. Put the obtained filter residue into a vacuum drying oven, set the temperature at 70 °C, and dry for 12 h to obtain crude silicon A. Weigh 200 g of crude silicon A and place it in a square crucible. Roast it in a high-temperature roasting furnace under a nitrogen-hydrogen mixed atmosphere for 3 h to obtain crude silicon B. After cooling, take out crude silicon B, place it in a stirring tank, add 2 L of ethylene glycol and 2 g of sodium dodecylbenzenesulfonate respectively. After stirring evenly, add 2 Kg of zirconia beads with a particle size of 0.1 mm into a grinding machine, turn on nitrogen protection, and grind at a speed of 1500 r / min for 5 h to obtain nano-silicon slurry. Add 20 ml of lithium sulfide reagent into the slurry, turn on mechanical stirring for 30 min, take out the slurry for spray drying, set the inlet air temperature at 90 °C and the outlet air temperature at 60 °C to obtain pre-treated nano-silicon powder. Weigh 50 g of the pre-treated nano-silicon powder and mix it evenly with 50 g of asphalt powder, put it into a coating machine, set the coating temperature at 600 °C, and perform high-temperature coating under a nitrogen atmosphere for 3 h. After cooling, take it out to prepare a modified nano-silicon material. Example

[0018] Weigh 1000 g of industrial crude silicon and put it into a crusher for multiple crushing. After sieving through a 50-mesh sieve, put it into a stirring tank. Add 2 L of dilute hydrochloric acid solution with a concentration of 1 mol / L into the tank, stir at 100 r / min for 2 h, filter and wash with deionized water. Put the obtained filter residue into a vacuum drying oven, set the temperature at 70 °C, and dry for 12 h to obtain crude silicon A. Weigh 200 g of crude silicon A and place it in a square crucible. Roast it in a high-temperature roasting furnace under a nitrogen-hydrogen mixed atmosphere for 3 h to obtain crude silicon B. After cooling, take out crude silicon B, place it in a stirring tank, add 2 L of ethylene glycol and 2 g of sodium dodecylbenzenesulfonate respectively. After stirring evenly, add 2 Kg of zirconia beads with a particle size of 0.1 mm into a grinder, turn on nitrogen protection, and grind at a speed of 1500 r / min for 5 h to obtain nano-silicon slurry. Add 10 ml of lithium sulfide reagent into the slurry, turn on mechanical stirring for 30 min, take out the slurry for spray drying, set the inlet air temperature at 90 °C and the outlet air temperature at 60 °C to obtain pretreated nano-silicon powder. Weigh 50 g of the pretreated nano-silicon powder and mix it evenly with 50 g of asphalt powder, put it into a coating machine, set the coating temperature at 700 °C, and perform high-temperature coating under a nitrogen atmosphere for 3 h. After cooling, take it out to prepare a modified nano-silicon material. Example

[0019] Weigh 1000 g of industrial crude silicon and put it into a crusher for multiple crushing. After sieving through a 50-mesh sieve, put it into a stirring tank. Add 2 L of dilute hydrochloric acid solution with a concentration of 1 mol / L into the tank, stir at 100 r / min for 2 h, filter and wash with deionized water. Put the obtained filter residue into a vacuum drying oven, set the temperature at 70 °C, and dry for 12 h to obtain crude silicon A. Weigh 200 g of crude silicon A and place it in a square crucible. Roast it in a high-temperature roasting furnace under a nitrogen-hydrogen mixed atmosphere for 3 h to obtain crude silicon B. After cooling, take out crude silicon B, place it in a stirring tank, add 2 L of ethylene glycol and 20 g of sodium dodecylbenzenesulfonate respectively. After stirring evenly, add 2 Kg of zirconia beads with a particle size of 0.1 mm into a grinder, turn on nitrogen protection, and grind at a speed of 1500 r / min for 5 h to obtain nano-silicon slurry. Add 10 ml of lithium sulfide reagent into the slurry, turn on mechanical stirring for 30 min, take out the slurry for spray drying, set the inlet air temperature at 90 °C and the outlet air temperature at 60 °C to obtain pretreated nano-silicon powder. Weigh 50 g of the pretreated nano-silicon powder and mix it evenly with 50 g of asphalt powder, put it into a coating machine, set the coating temperature at 1100 °C, and perform high-temperature coating under a nitrogen atmosphere for 3 h. After cooling, take it out to prepare a modified nano-silicon material.

[0020] Weigh 1000 g of industrial crude silicon and put it into a crusher for multiple crushing. After screening through a 50-mesh sieve, put it into a stirring tank. Add 2 L of dilute hydrochloric acid solution with a concentration of 1 mol / L into the tank, stir at 100 r / min for 2 h, filter and wash with deionized water, put the obtained filter residue into a vacuum drying oven, set the temperature at 70 °C, and dry for 12 h to obtain crude silicon A; Weigh 200 g of crude silicon A and place it in a square crucible. Roast it in a high-temperature roasting furnace under a nitrogen-hydrogen mixed atmosphere for 3 h to obtain crude silicon B; After cooling, take out crude silicon B, place it in a stirring tank, add 2 L of ethylene glycol and 2 g of sodium dodecylbenzenesulfonate respectively. After stirring evenly, add 2 Kg of zirconia beads with a particle size of 0.1 mm into a grinder, turn on nitrogen protection, and grind at a speed of 1500 r / min for 5 h to obtain nano-silicon slurry; Add 0 ml of lithium sulfide reagent into the slurry, turn on mechanical stirring for 30 min, take out the slurry for spray drying, set the inlet air temperature at 90 °C and the outlet air temperature at 60 °C to obtain pre-treated nano-silicon powder; Weigh 50 g of the pre-treated nano-silicon powder and mix it evenly with 50 g of asphalt powder, put it into a coating machine, set the coating temperature at 1100 °C, and perform high-temperature coating under a nitrogen atmosphere for 3 h. After cooling, take it out to prepare a modified nano-silicon material.

[0021] Weigh 1000 g of industrial crude silicon and put it into a crusher for multiple crushing. After screening through a 50-mesh sieve, put it into a stirring tank. Add 2 L of dilute hydrochloric acid solution with a concentration of 1 mol / L into the tank, stir at 100 r / min for 2 h, filter and wash with deionized water, put the obtained filter residue into a vacuum drying oven, set the temperature at 70 °C, and dry for 12 h to obtain crude silicon A; Weigh 200 g of crude silicon A and place it in a square crucible. Roast it in a high-temperature roasting furnace under a nitrogen-hydrogen mixed atmosphere for 3 h to obtain crude silicon B; After cooling, take out crude silicon B, place it in a stirring tank, add 2 L of ethylene glycol and 2 g of sodium dodecylbenzenesulfonate respectively. After stirring evenly, add 2 Kg of zirconia beads with a particle size of 0.1 mm into a grinder, turn on nitrogen protection, and grind at a speed of 1500 r / min for 5 h to obtain nano-silicon slurry; Add 0 ml of lithium sulfide reagent into the slurry, turn on mechanical stirring for 30 min, take out the slurry for spray drying, set the inlet air temperature at 90 °C and the outlet air temperature at 60 °C to obtain pre-treated nano-silicon powder; Weigh 50 g of the pre-treated nano-silicon powder and mix it evenly with 30 g of graphite powder, put it into a coating machine, set the coating temperature at 1100 °C, and perform high-temperature coating under a nitrogen atmosphere for 3 h. After cooling, take it out to prepare a modified nano-silicon material.

[0022] Use the modified nano-silicon materials obtained in Examples 1, 2, 3, 4, 5 and Comparative Examples 1 and 2 as the negative active material of a coin-type lithium-ion battery respectively. The manufacturing steps are as follows: 1. Batching and stirring: According to active material:conductive agent:CMC:SBR = 8:1:1:1, stir to obtain a viscous paste. 2. Coating the slurry on the copper foil to make the electrode sheet, performing rolling after coating, and then baking at 200 °C for 4 hours; 3. Assembling the battery: using the lithium sheet as the negative electrode, polypropylene as the separator, adding the electrolyte to assemble a button cell, and evaluating the electrochemical performance of the material.

[0023] The specific results of the button cell tests made of the materials obtained in Examples 1, 2, 3, 4, 5 and Comparative Examples 1 and 2 are shown in Table 1.

[0024]

[0025] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent transformation made by using the content of the specification of the present invention, or directly or indirectly applied in the relevant technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A preparation method of modified nano-silicon powder for silicon-carbon negative electrode, characterized in that: The preparation method includes the following steps: Step 1: After crushing industrial crude silicon or photovoltaic silicon waste into millimeter-sized small particles, add an acidic solution thereto, stir and wash, and after filtration, dry the crude silicon to obtain crude silicon A for standby; Step 2: Take out the dried crude silicon A and roast it in a reducing atmosphere to obtain crude silicon B; Step 3: Mix crude silicon B with a grinding aid and a dispersant and stir, add a grinding medium, and fully grind it in an inert atmosphere to prepare a nano-silicon slurry; Step 4: Add a lithium-containing reagent to the above nano-silicon slurry, stir and disperse it to form a lithium-containing film on the surface of the silicon; Step 5: Dry the above nano-silicon slurry to prepare nano-silicon powder; Step 6: Fully mix the above nano-silicon powder with a soft carbon material and perform high-temperature coating to prepare modified nano-silicon powder.

2. The preparation method of the modified nano-silicon powder for silicon-carbon negative electrode according to claim 1, characterized in that: In Step 1, the particle size of the crushed industrial crude silicon or photovoltaic waste silicon is 1 mm - 5 mm; the acidic solution is one or more of dilute hydrochloric acid, dilute sulfuric acid, acetic acid, and dilute nitric acid; the drying temperature is 50 - 90 °C.

3. The preparation method of modified nano-silicon powder for silicon-carbon negative electrode according to claim 1, wherein: In Step 1, the reducing atmosphere is one of hydrogen, carbon monoxide, nitrogen-hydrogen mixture, and carbon monoxide mixture; the roasting temperature is 400 - 800 °C.

4. The preparation method of the modified nano-silicon powder for silicon-carbon negative electrode according to claim 1, characterized in that: In Step 3, the grinding aid is one or more of methanol, ethanol, ethylene glycol, and methyl pentanol, and the dispersant is one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, and ethylenediaminetetraacetic acid; the grinding medium is a mixture of one or more specifications of agate balls and zirconia balls; the inert atmosphere is one of nitrogen, argon, and neon.

5. The preparation method of modified nano-silicon powder for silicon-carbon negative electrode according to claim 1, characterized in that: In Step 4, the lithium-containing reagent is one or more of lithium sulfide, lithium oxide, and lithium-silicon compounds.

6. The preparation method of the modified nano-silicon powder for silicon-carbon negative electrode according to claim 1, characterized in that: In Step 5, the drying method is one of spray drying, flash drying, and rotary distillation.

7. The preparation method of modified nano-silicon powder for silicon-carbon anode according to claim 1, characterized in that: In Step 6, the soft carbon material is one or more of resin, asphalt, and sucrose; the high-temperature coating temperature is between 500 - 1100 °C.

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