Production method of silicon-carbon negative electrode material

Abstract

The invention discloses a production method of a silicon-carbon negative electrode material, which adopts a production process route that hydrogen is used as carrier gas to charge silane, low-temperature hydrogen is used as carrier gas to charge acetylene for passivation, and high-temperature argon is used as carrier gas to charge acetylene for carbon coating, so that the existence of nitrogen during the existence of high-activity nano silicon is avoided, and an exothermic reaction causing explosion is eliminated; and the ton-level scale of single-furnace capacity is realized, and silicon-carbon negative electrode material products can be safely produced in batches.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery negative electrode material preparation, and in particular to a method for producing a silicon-carbon negative electrode material. Background Art

[0002] Lithium-ion batteries are the mainstream power batteries in today's new energy vehicle field and the "heart system" of electric vehicles. Their performance plays a key role in the operation of the vehicle and restricts the popularization and development of electric vehicles.

[0003] Negative electrode materials are an important component that affects the range, charging efficiency, and safety of lithium-ion batteries. To date, graphite negative electrodes have approached the theoretical specific capacity limit of 372mAh / g, which cannot meet the market demand for high-energy-density lithium batteries. There is an urgent need for better negative electrode materials. Silicon-based negative electrodes are currently the materials with the highest theoretical efficiency and are closest to industrialization. Among them, the new generation of silicon-carbon negative electrode materials are the best performing silicon-based negative electrodes and are the most suitable high-capacity, long-cycle negative electrode materials for lithium-ion battery applications. However, the nano-silicon produced during the production of this material has very high activity and will undergo a violent exothermic reaction with nitrogen at a certain temperature. At present, other manufacturers use nitrogen as a carrier gas in the production of this material, which has led to frequent safety accidents such as combustion and explosion in various production companies. As of now, although the product has achieved pilot production, it is still not available for large-scale mass production due to safety reasons. It cannot meet the mass production needs of new energy vehicles, energy storage and other fields, and has not yet been truly commercialized. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for producing silicon-carbon negative electrode materials, eliminating the exothermic reaction that leads to explosion, achieving a single furnace production capacity of tons, and enabling safe batch production.

[0005] The technical solution adopted in the present invention is: A method for producing a silicon-carbon negative electrode material, comprising the following steps: S1: Raw material preparation; porous carbon requires pore volume 0.65 ml / g~0.85 ml / g, pore diameter ≤2nm, specific gravity 1500~1900m 2 / g; S2: Loading the furnace; loading the porous carbon into the furnace according to the capacity of the fluidized bed; S3: Replacement: nitrogen with a purity of ≥99.999% is introduced into the fluidized bed to replace the air in the furnace until the oxygen content is ≤100ppm; S4: One-time carrier gas switching; after the replacement is completed, the nitrogen is switched to hydrogen with a purity of ≥99.999%; S5: Heating: After the carrier gas is switched to hydrogen, the temperature is raised to 400°C to 500°C. The pressure in the furnace is ≤20kPa during the heating process. S6: Filling silane: Using hydrogen as the carrier gas, fill the fluidized bed with silane with a purity of ≥99.9999% to perform silicon deposition; S7: Low-temperature acetylene charging: After silicon deposition is completed, the temperature in the fluidized bed is maintained at 400°C to 500°C, and acetylene with a purity of ≥99% is charged into the fluidized bed to the required amount using hydrogen as a carrier gas; S8: Secondary carrier gas switching: After the low-temperature acetylene filling is completed, the hydrogen gas is switched to argon gas with a purity of ≥99.999%; S9: Heating: After the secondary carrier gas is switched, the temperature in the fluidized bed is raised to 500°C to 600°C; S10: High-temperature acetylene charging: After the temperature is raised, argon is used as the carrier gas to charge acetylene with a purity of ≥99% to the required amount; S11: Cooling down; after the high-temperature acetylene filling is completed, the temperature in the fluidized bed is controlled to drop to 400°C, and the carrier gas is switched to nitrogen with a purity of ≥99.999%; S12: Unloading; when the temperature in the fluidized bed drops below 50°C, unloading is performed; S13: Screening, demagnetization and packaging: After the product is taken out of the oven, screening, demagnetization and packaging are carried out.

[0006] Specifically, in step S2, the weight of a 20kg fluidized bed furnace is 10kg±0.5kg; the weight of a 100kg fluidized bed furnace is 50kg±1kg; and the weight of a 1000kg fluidized bed furnace is 500kg±1kg.

[0007] Specifically, in step S3, the nitrogen replacement flow rate of the 20kg fluidized bed is 50L / min to 100L / min; the nitrogen replacement flow rate of the 100kg fluidized bed is 100L / min to 300L / min; and the nitrogen replacement flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

[0008] Specifically, in the S4, the hydrogen flow rate of the 20kg fluidized bed is 30L / min to 80L / min; the hydrogen flow rate of the 100kg fluidized bed is 80L / min to 300L / min; and the hydrogen flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

[0009] Specifically, in S6, the specific control parameters for silane filling are: 20kg fluidized bed: hydrogen flow rate 40L / min~70L / min, silane flow rate 5L / min~30L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, silane flow rate 5m 3 ~15m3 ; 100kg fluidized bed: hydrogen flow rate 100L / min~300L / min, silane flow rate 10L / min~80L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, silane feed rate 30m 3 ~50m 3 ; 1000kg fluidized bed: hydrogen flow rate 150L / min~450L / min, silane flow rate 50L / min~180L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, silane feed rate 300m 3 ~600m 3 .

[0010] Specifically, in S7, the specific control parameters for low-temperature acetylene charging are: 20kg fluidized bed: hydrogen flow rate 40L / min~70L / min, acetylene flow rate 5L / min~30L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, acetylene flow rate 100L~1000L; 100kg fluidized bed: hydrogen flow rate 100L / min~300L / min, acetylene flow rate 10L / min~80L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, acetylene flow rate 1000L~5000L; 1000kg fluidized bed: hydrogen flow rate 150L / min~450L / min, acetylene flow rate 10L / min~160L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, acetylene flow rate 5m 3 ~50m 3 .

[0011] Specifically, in the secondary carrier gas switching in S8, the argon flow rate of the 20kg fluidized bed is 30L / min to 80L / min; the argon flow rate of the 100kg fluidized bed is 80L / min to 300L / min; and the argon flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

[0012] Specifically, in S10, the specific control parameters for high-temperature acetylene charging are: 20kg fluidized bed: argon flow rate 40L / min~70L / min, acetylene flow rate 5L / min~30L / min, furnace pressure ≤20kPa, temperature 500℃~600℃, acetylene flow rate 5m 3 ~15m 3 ; 100kg fluidized bed: argon flow rate 100L / min~300L / min, acetylene flow rate 10L / min~80L / min, furnace pressure ≤20kPa, temperature 500℃~600℃, acetylene flow rate 10m 3 ~30m 3 ; 1000kg fluidized bed: argon flow rate 150L / min~450L / min, acetylene flow rate 30L / min~160L / min, furnace pressure ≤20kPa, temperature 500℃~600℃, acetylene flow rate 80m 3 ~400m 3 .

[0013] Specifically, in the S11, the nitrogen flow rate of the 20kg fluidized bed is 30L / min to 80L / min; the nitrogen flow rate of the 100kg fluidized bed is 80L / min to 300L / min; and the nitrogen flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

[0014] Due to the adoption of the above technical solution, the present invention has the following advantages: The present invention adopts a production process route of hydrogen as carrier gas for silane filling + low-temperature hydrogen as carrier gas for acetylene passivation + high-temperature argon as carrier gas for acetylene carbon coating, which avoids the presence of nitrogen during the presence of highly active nano-silicon, eliminates the exothermic reaction that causes explosion, achieves a single furnace production capacity of tons, and can safely produce silicon-carbon negative electrode material products in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a production flow chart of the present invention. DETAILED DESCRIPTION

[0016] The present invention is further explained below by Examples 1-3, which are not intended to limit the scope of protection of the present invention. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. Example 1

[0017] A method for producing a silicon-carbon negative electrode material, comprising the following steps: S1: Raw material preparation; porous carbon requires pore volume 0.65 ml / g, pore diameter 1.75nm, specific surface area 1630m 2 / g.

[0018] S2: Charging the furnace; 10 kg of porous carbon was loaded into a fluidized bed with a capacity of 20 kg.

[0019] S3: Replacement: Nitrogen with a purity of ≥99.999% is introduced into the fluidized bed to replace the air in the furnace until the oxygen content is 30ppm; the nitrogen replacement flow rate is 90L / min.

[0020] S4: One-time carrier gas switching; after the replacement is completed, the nitrogen is switched to hydrogen with a purity of ≥99.999% and a hydrogen flow rate of 60L / min.

[0021] S5: Heating: After the carrier gas is switched to hydrogen, the temperature is raised to 400°C. During the heating process, the pressure in the furnace is controlled below 15 kPa.

[0022] S6: Filling silane; using hydrogen as carrier gas, fill 8m 3 Silicon deposition was performed using silane with a purity of ≥99.9999%; the hydrogen flow rate was 60 L / min, the silane flow rate was 10 L / min, the furnace pressure was below 15 kPa, and the temperature was 400°C.

[0023] S7: Fill acetylene at low temperature; after the silane is introduced, 500L of acetylene with a purity of ≥99% is introduced into the fluidized bed using hydrogen as the carrier gas; the hydrogen flow rate is 60L / min, the acetylene flow rate is 10L / min, the pressure in the furnace is below 15kPa, and the temperature is 400℃.

[0024] S8: Secondary carrier gas switching; after low-temperature acetylene filling is completed, the hydrogen gas is switched to argon gas with a purity of ≥99.999%; the argon gas flow rate is 60L / min.

[0025] S9: Heating: After the secondary carrier gas is switched, the temperature in the fluidized bed is raised to 500°C.

[0026] S10: High temperature acetylene filling; after heating to 500℃, argon is used as carrier gas and 7m 3 Acetylene with a purity of ≥99%; argon flow rate 60L / min, acetylene flow rate 20L / min, furnace pressure below 15kPa.

[0027] S11: Cooling down; after the high-temperature acetylene filling is completed, the temperature in the fluidized bed is controlled to drop to 400°C, and the carrier gas is switched to nitrogen with a purity of ≥99.999%; the nitrogen flow rate is 60L / min.

[0028] S12: Unloading; when the temperature in the fluidized bed drops below 50°C, unloading is carried out.

[0029] S13: Screening, demagnetization and packaging: After the product is taken out of the oven, screening, demagnetization and packaging are carried out. Example 2

[0030] A method for producing a silicon-carbon negative electrode material, comprising the following steps: S1: Raw material preparation; porous carbon requires pore volume 0.75 ml / g, pore diameter 1.85nm, specific surface area 1690m 2 / g.

[0031] S2: Furnace charging; 50 kg of porous carbon is loaded into a fluidized bed with a capacity of 100 kg.

[0032] S3: Replacement: Nitrogen with a purity of ≥99.999% is introduced into the fluidized bed to replace the air in the furnace until the oxygen content is 30ppm; the nitrogen replacement flow rate is 250L / min.

[0033] S4: One-time carrier gas switching; after the replacement is completed, the nitrogen is switched to hydrogen with a purity of ≥99.999% and a hydrogen flow rate of 250L / min.

[0034] S5: Heating: After the carrier gas is switched to hydrogen, the temperature is raised to 450°C. During the heating process, the pressure in the furnace is controlled below 15 kPa.

[0035] S6: Filling silane; using hydrogen as carrier gas, fill 40m3 of silane into the fluidized bed. 3 Silicon deposition was performed using silane with a purity of ≥99.9999%; the hydrogen flow rate was 250 L / min, the silane flow rate was 50 L / min, the furnace pressure was below 15 kPa, and the temperature was 450°C.

[0036] S7: Low-temperature acetylene filling; after silicon deposition is completed, 3000L of acetylene with a purity of ≥99% is filled into the fluidized bed using hydrogen as the carrier gas; the hydrogen flow rate is 250L / min, the acetylene flow rate is 40L / min, the pressure in the furnace is below 15kPa, and the temperature is 450℃.

[0037] S8: Secondary carrier gas switching; after low-temperature acetylene filling is completed, hydrogen is switched to argon with a purity of ≥99.999%; the argon flow rate is 250L / min.

[0038] S9: Heating: After the secondary carrier gas is switched, the temperature in the fluidized bed is raised to 550°C.

[0039] S10: High temperature acetylene filling; after heating to 550℃, argon is used as carrier gas and 20m 3 Acetylene with a purity of ≥99%; argon flow rate of 250L / min, acetylene flow rate of 40L / min, and furnace pressure below 15kPa.

[0040] S11: Cooling down; after the high-temperature acetylene filling is completed, the temperature in the fluidized bed is controlled to drop to 400°C, and the carrier gas is switched to nitrogen with a purity of ≥99.999%; the nitrogen flow rate is 250L / min.

[0041] S12: Unloading; when the temperature in the fluidized bed drops below 50°C, unloading is carried out.

[0042] S13: Screening, demagnetization and packaging: After the product is taken out of the oven, screening, demagnetization and packaging are carried out. Example 3

[0043] A method for producing a silicon-carbon negative electrode material, comprising the following steps: S1: Raw material preparation; porous carbon requires pore volume 0.85 ml / g, pore diameter 2nm, specific gravity 1900m 2 / g.

[0044] S2: Charging the furnace; 500 kg of porous carbon is loaded into a fluidized bed with a capacity of 1000 kg.

[0045] S3: Replacement: Nitrogen with a purity of ≥99.999% is introduced into the fluidized bed to replace the air in the furnace until the oxygen content is 30ppm; the nitrogen replacement flow rate is 500L / min.

[0046] S4: One-time carrier gas switching; after the replacement is completed, the nitrogen is switched to hydrogen with a purity of ≥99.999% and a hydrogen flow rate of 400 L / min.

[0047] S5: Heating: After the carrier gas is switched to hydrogen, the temperature is raised to 500°C. During the heating process, the pressure in the furnace is controlled below 20 kPa.

[0048] S6: Filling silane; using hydrogen as carrier gas, fill 500m3 of silane into the fluidized bed. 3 Silicon deposition was performed using silane with a purity of ≥99.9999%; the hydrogen flow rate was 400 L / min, the silane flow rate was 180 L / min, the furnace pressure was 20 kPa, and the temperature was 500°C.

[0049] S7: Low temperature acetylene filling; after the silane is introduced, hydrogen is used as the carrier gas to fill the fluidized bed with acetylene with a purity of ≥99% for 30 m 3 ; Hydrogen flow rate 400L / min, acetylene flow rate 80L / min, furnace pressure below 20kPa, temperature 500℃.

[0050] S8: Secondary carrier gas switching; after low-temperature acetylene filling is completed, the hydrogen gas is switched to argon gas with a purity of ≥99.999%; the argon gas flow rate is 400L / min.

[0051] S9: Heating: After the secondary carrier gas is switched, the temperature in the fluidized bed is raised to 600°C.

[0052] S10: High temperature acetylene filling; after heating to 600℃, argon is used as carrier gas and 300m 3 Acetylene with a purity of ≥99%; argon flow rate 400L / min, acetylene flow rate 130L / min, furnace pressure below 20kPa.

[0053] S11: Cooling down; after the high-temperature acetylene charging is completed, the temperature in the fluidized bed is controlled to drop to 400°C, and the carrier gas is switched to nitrogen with a purity of ≥99.999%; the nitrogen flow rate is 400L / min.

[0054] S12: Unloading; when the temperature in the fluidized bed drops below 50°C, unloading is carried out.

[0055] S13: Screening, demagnetization and packaging: After the product is taken out of the oven, screening, demagnetization and packaging are carried out.

[0056] The silicon-carbon negative electrode materials produced by the production methods of Examples 1-3 above were tested, and the material characterization method was as follows: (1) Material resistivity test method: Use a dedicated powder resistivity tester with an evaluation pressure of 20 MPa; (2) The first capacity and first efficiency tests of the materials were characterized using button cells, with a lithium metal sheet as the counter electrode, a charge and discharge rate of 0.1C, and a charge and discharge voltage range of 0.005V to 1.5V; (3) Material ratio test method: BET ratio tester is used for testing; (4) Material tap density test method: Use a tap density tester for testing; (5) Silicon content test method: Calcination in a muffle furnace is used for testing.

[0057] The test results are shown in the following table:

[0058] Through the production verification of Examples 1-3 of the present invention, the production technology of the present invention has a safe and reliable production process, stable product quality, high pass rate, and can meet the needs of large-scale mass production.

[0059] The parts not described in detail in this invention are prior art.

[0060] The embodiments selected herein for the purpose of disclosing the invention are presently considered suitable, but it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of the concept and invention.

Claims

1. A method for producing a silicon-carbon negative electrode material, characterized in that: The specific steps are: S1: Raw material preparation; porous carbon requires pore volume 0.65 ml / g~0.85 ml / g, pore diameter ≤2nm, specific gravity 1500~1900m 2 / g; S2: Furnace loading: porous carbon is loaded into the furnace according to the capacity of the fluidized bed; S3: Replacement: nitrogen with a purity of ≥99.999% is introduced into the fluidized bed to replace the air in the furnace until the oxygen content is ≤100ppm; S4: One-time carrier gas switching; after the replacement is completed, the nitrogen is switched to hydrogen with a purity of ≥99.999%; S5: Heating: After the carrier gas is switched to hydrogen, the temperature is raised to 400°C to 500°C. The pressure in the furnace is ≤20kPa during the heating process. S6: silane filling; Using hydrogen as carrier gas, silane with a purity of ≥99.9999% is charged into the fluidized bed for silicon deposition; S7: Low-temperature acetylene charging: After silicon deposition is completed, the temperature in the fluidized bed is maintained at 400°C to 500°C, and acetylene with a purity of ≥99% is charged into the fluidized bed to the required amount using hydrogen as a carrier gas; S8: Secondary carrier gas switching: After the low-temperature acetylene filling is completed, the hydrogen gas is switched to argon gas with a purity of ≥99.999%; S9: Heating: After the secondary carrier gas is switched, the temperature in the fluidized bed is raised to 500°C to 600°C; S10: High-temperature acetylene charging: After the temperature is raised, argon is used as the carrier gas to charge acetylene with a purity of ≥99% to the required amount; S11: Cooling down; after the high-temperature acetylene filling is completed, the temperature in the fluidized bed is controlled to drop to 400°C, and the carrier gas is switched to nitrogen with a purity of ≥99.999%; S12: Unloading; when the temperature in the fluidized bed drops below 50°C, unloading is performed; S13: Screening, demagnetization and packaging: After the product is taken out of the furnace, screening, demagnetization and packaging are carried out.

2. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: In step S2, the weight of a 20kg fluidized bed furnace is 10kg±0.5kg; the weight of a 100kg fluidized bed furnace is 50kg±1kg; and the weight of a 1000kg fluidized bed furnace is 500kg±1kg.

3. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: In step S3, the nitrogen replacement flow rate of the 20kg fluidized bed is 50L / min to 100L / min; the nitrogen replacement flow rate of the 100kg fluidized bed is 100L / min to 300L / min; and the nitrogen replacement flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

4. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: In the S4, the hydrogen flow rate of the 20kg fluidized bed is 30L / min to 80L / min; the hydrogen flow rate of the 100kg fluidized bed is 80L / min to 300L / min; and the hydrogen flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

5. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: In the above-mentioned S6, the specific control parameters of silane filling are: 20kg fluidized bed: hydrogen flow rate 40L / min~70L / min, silane flow rate 5L / min~30L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, silane flow rate 5m 3 ~15m 3 ; 100kg fluidized bed: hydrogen flow rate 100L / min~300L / min, silane flow rate 10L / min~80L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, silane feed rate 30m 3 ~50m 3 ; 1000kg fluidized bed: hydrogen flow rate 150L / min~450L / min, silane flow rate 50L / min~180L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, silane feed rate 300m 3 ~600m 3 .

6. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: In the above-mentioned S7, the specific control parameters of low-temperature acetylene charging are: 20kg fluidized bed: hydrogen flow rate 40L / min~70L / min, acetylene flow rate 5L / min~30L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, acetylene flow rate 100L~1000L; 100kg fluidized bed: hydrogen flow rate 100L / min~300L / min, acetylene flow rate 10L / min~80L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, acetylene flow rate 1000L~5000L; 1000kg fluidized bed: hydrogen flow rate 150L / min~450L / min, acetylene flow rate 10L / min~160L / min, furnace pressure ≤20kPa, temperature 400℃~500℃, acetylene flow rate 5m 3 ~50m 3 .

7. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: The secondary carrier gas switching in the S8 is as follows: the argon flow rate of the 20kg fluidized bed is 30L / min to 80L / min; the argon flow rate of the 100kg fluidized bed is 80L / min to 300L / min; the argon flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

8. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: In the above-mentioned S10, the specific control parameters of high-temperature acetylene charging are: 20kg fluidized bed: argon flow rate 40L / min~70L / min, acetylene flow rate 5L / min~30L / min, furnace pressure ≤20kPa, temperature 500℃~600℃, acetylene flow rate 5m 3 ~15m 3 ; 100kg fluidized bed: argon flow rate 100L / min~300L / min, acetylene flow rate 10L / min~80L / min, furnace pressure ≤20kPa, temperature 500℃~600℃, acetylene flow rate 10m 3 ~30m 3 ; 1000kg fluidized bed: argon flow rate 150L / min~450L / min, acetylene flow rate 30L / min~160L / min, furnace pressure ≤20kPa, temperature 500℃~600℃, acetylene flow rate 80m 3 ~400m 3 .

9. The method for producing a silicon-carbon negative electrode material according to claim 1, wherein: In the S11, the nitrogen flow rate of the 20kg fluidized bed is 30L / min to 80L / min; the nitrogen flow rate of the 100kg fluidized bed is 80L / min to 300L / min; and the nitrogen flow rate of the 1000kg fluidized bed is 300L / min to 500L / min.

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