CN111785944B - Method for preparing porous silicon/carbon/nanometal composite anode material by cutting silicon waste by plasma activation - Google Patents

Abstract

The invention relates to a method for preparing a porous silicon/carbon/nano metal composite anode material by plasma activation and cutting of silicon waste, belonging to the technical fields of new energy materials and electrochemistry. According to the invention, the silicon waste material obtained by cutting the diamond wire and the carbon source powder are uniformly mixed and subjected to plasma activation treatment, the silicon and the carbon are gasified, condensed and recrystallized to obtain the nano silicon/carbon composite material, the plasma activation treatment can remove impurities in the silicon waste material and realize the nanocrystallization of the silicon and the carbon, and the nano metal particles of the silicon/carbon composite material are compounded to prepare the porous silicon/carbon/nano metal composite material. The porous silicon/carbon/nano metal composite anode material prepared by the invention can shorten the transmission distance of lithium ions and electrons, improve the overall conductivity and structural integrity of the electrode material, and effectively solve the problems of huge volume change and low rate capability in the lithium removal and intercalation process.

Description

Method for preparing porous silicon/carbon/nanometal composite anode material by cutting silicon waste by plasma activation

technical field

The invention relates to a method for preparing a porous silicon/carbon/nano-metal composite negative electrode material by cutting silicon waste through plasma activation, and belongs to the technical fields of new energy materials and electrochemistry.

Background technique

In the lithium-ion battery structure, the anode material is a very important component, which directly determines the quality and application of the lithium-ion battery. So far, lithium-ion battery anode materials mainly include carbon materials, lithium alloys (lithium-silicon alloys, lithium-tin alloys, etc.), transition metal oxides (TiO ₂ , SnO _{2 ,} etc.), and nitrides. Because graphite materials have good cycle stability, excellent electrical conductivity, and their layered structure has a good space for intercalation of lithium, the volume change in the process of intercalation and deintercalation of lithium is within an acceptable range. Graphite negative electrode materials are widely used in the lithium battery industry. application. However, with the rapid development of electronic technology and the rapid popularization of electric vehicles, the market demand for high specific capacity lithium-ion batteries is becoming stronger and stronger. However, the theoretical discharge specific capacity of commercialized graphite anode materials is only 372mAh/g, and the actual capacity of graphite anode materials put into production is already very close to this, which is difficult to meet the requirements of power lithium-ion batteries in the field of electric vehicles and electronics The demand for high-energy energy storage devices in the industrial field. Therefore, the development of lithium-ion battery anode materials with high discharge specific capacity is an urgent problem to be solved.

Si anode material has a high theoretical specific capacity, up to 4200mAh/g, and at the same time has the advantages of low voltage platform, low reactivity with electrolyte, abundant reserves in the earth's crust, and low price. It is a very promising Lithium battery anode material, but Si anode also has fatal defects, namely the huge volume change and low intrinsic conductivity during charging and discharging. Volume expansion is a problem that any Li-ion electrode material must face during the process of delithiation and lithium intercalation, but this problem is particularly serious for Si anodes. In the state of fully intercalating lithium, the volume expansion of the Si negative electrode can reach 300%, which will not only cause cracks or even breakage of the Si negative electrode, but also destroy the structure of the negative electrode sheet, resulting in irreversible loss of battery capacity and safety hazards. In addition, the intrinsic semiconductor nature of silicon is also a problem that cannot be ignored. Due to the low intrinsic conductivity of Si, the rate performance of the battery is severely limited, which directly affects its practical application value.

In recent years, most manufacturers at home and abroad have widely used diamond wire cutting technology to process silicon wafers in the production process of silicon wafers. During the online cutting of solar silicon wafers, due to the collision and friction between the wire cutting tool and the silicon wafer, in addition to the broken silicon particles produced, the tool will also be partially broken and worn, and the lubricating fluid and cooling fluid during the cutting process will also be mixed In the cutting system, the formation of cutting silicon waste will waste about 40% of high-purity silicon. Taking 2019 alone as an example, to realize the cutting of 132GW silicon wafers, up to 300,000 tons of cutting waste will be generated. However, the effective recovery of high-purity silicon powder in waste materials is difficult to achieve according to the current recovery methods such as flotation and cyclone separation, and silicon is seriously polluted during the cutting process, so it cannot be directly used in the photovoltaic and electronic industries.

Contents of the invention

The present invention aims at the problems of high cost of lithium battery silicon negative electrode in the prior art, huge volume change during the cycle of silicon material, low intrinsic conductivity, and difficult recycling of silicon waste cut by diamond wire in the photovoltaic industry, and provides a method for preparing porous silicon waste by plasma activation cutting The method of silicon/carbon/nano-metal composite negative electrode material is to mix the diamond wire cut silicon waste with carbon source powder and undergo plasma activation treatment, silicon and carbon gasification, condensation and recrystallization to obtain nano-silicon/carbon composite material, plasma activation treatment can The impurity in the silicon waste is removed and the nanometerization of silicon and carbon is realized, and the silicon/carbon composite material is compounded with nano-metal particles to prepare a porous silicon/carbon/nano-metal composite material. The present invention adopts the combined treatment method of plasma activation composite-nano-metal particle composite phase to prepare cut silicon waste into a high-performance negative electrode material for lithium-ion batteries, that is, porous silicon/carbon/nano-metal composite negative electrode, which can shorten the transmission distance of lithium ions and electrons , improve the overall conductivity and structural integrity of the electrode material, and effectively solve the problems of huge volume change and low rate performance during the lithium-deintercalation process.

A method for preparing a porous silicon/carbon/nano-metal composite negative electrode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) Diamond wire cutting silicon waste is crushed, ground, and vacuum-dried to obtain waste silicon powder;

(2) Mixing waste silicon powder and carbon source in step (1) evenly and vacuum drying to obtain silicon-carbon mixed powder;

(3) Pass argon gas into the plasma furnace to get rid of the air in the furnace body, and use argon gas as protective gas and carrier gas, pass step (2) silicon-carbon mixed powder into the plasma furnace for plasma activation treatment, silicon Carbon mixed powder is gasified, condensed and recrystallized to obtain nano-silicon/carbon composite material (PSi/C nano-composite material);

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-metal salt-alcohol solution system for compounding metal particles and nanoparticles, wash with deionized water, and separate solid-liquid to obtain nano-metal particle composite silicon/carbon Composite material, nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain porous silicon/carbon/nano-metal composite material (PSi/C/Nano-M composite material).

The mass fraction of the waste silicon powder in the silicon-carbon mixed powder in the step (2) is 3-100%. The mixing method of waste silicon powder and carbon source is manual mixing, mechanical stirring, ball milling or high energy ball milling;

The carbon source in the step (2) is glucose, fructose, sucrose, xylose, sorbose, citric acid, starch, polyethylene, polypropylene, cellulose, graphite, graphene, carbon nanotubes, aromatic hydrocarbons, aromatic lipids One or more of petroleum asphalt or coal tar pitch.

The power of the plasma activation treatment in the step (3) is 10-150KW, the argon pressure is 0.10-0.70Mpa, and the feed rate of the silicon-carbon mixed powder is 1-50g/min.

Gasification, condensation and recrystallization of silicon-carbon mixed powder makes carbon composite on the silicon surface to obtain nano-silicon/carbon composite material. , the particle size of the nano-silicon/carbon composite material is controllable, and the particle size is 10-150nm;

In the step (4), the HF concentration in the HF-metal salt-alcohol solution system is 0.1-15 mol/L, the metal salt concentration is 0.005-10 mol/L, and the alcohol concentration is 0.1-20 mol/L;

Further, the metal salt is one or more of silver salt, copper salt, cobalt salt, nickel salt, aluminum salt, titanium salt, and the alcohols are methanol, ethanol, propanol, butanol, ethylene glycol, One or more of propylene glycol, propylene alcohol, and vinyl alcohol.

Preferably, the silver salt is AgNO ₃ , Ag ₂ SO ₄ or Ag ₂ CO ₃ , the copper salt is Cu(NO ₃ ) ₂ , CuSO ₄ or CuCO ₃ , the nickel salt is Ni(NO ₃ ) ₂ , NiSO ₄ or NiCO ₃ , cobalt salt is Co(NO ₃ ) ₂ , aluminum salt is Al(NO ₃ ) ₃ .

The liquid-solid ratio mL:g of the HF-metal salt-alcohol solution system to the nano-silicon/carbon composite material is (1-10):1.

The compounding temperature of the metal particles and nanoparticles is 20-80° C., and the time is 0.5-6 hours.

The beneficial effects of the present invention are:

(1) The porous silicon/carbon/nano-metal composite material of the present invention, its nanometer size and porous structure can effectively deintercalate the huge volume change in the lithium process, shorten the transmission distance of lithium ions and electrons simultaneously, metal particles and porous After silicon compounding, the problem of low conductivity of silicon materials can be effectively overcome, and the overall conductivity of the electrode material can be improved. The introduction of carbon can improve the stability of the overall structure of the material, and can also enhance the overall conductivity of the material again;

(2) The present invention prepares waste silicon powder into nanoscale through plasma activation process to solve the problem of poor intrinsic conductivity of silicon and huge volume expansion in the process of lithium deintercalation, carbon and metal ions effectively improve the low intrinsic conductivity of silicon The nanoscale of the porous silicon/carbon/nanometal composite can ensure the structural integrity of the electrode material during the charge-discharge cycle, thereby improving the cycle stability of the electrode, and the nanoscale effect can effectively accelerate the phase transition of the active material, reduce the The absolute volume effect of small active materials in the intercalation/delithiation process and the diffusion distance of lithium ions in the material;

(3) In the present invention, porous silicon/carbon/nano-metal composite anodes are prepared from photovoltaic wire-cut silicon waste as raw materials. The process is simple, suitable for industrial production, greatly saving raw material costs, improving resource utilization, and realizing turning waste into treasure. .

Description of drawings

Fig. 1 is the scanning electron microscope (SEM) figure of original diamond wire cutting silicon scrap in example 1;

Fig. 2 is the scanning electron microscope (SEM) figure of pSi/C/Nano-Ag composite material among the example 1;

Fig. 3 is a cycle performance curve at a rate of 0.5C after the original silicon waste and the porous silicon/carbon/nano-silver composite material are assembled into a half-cell in Example 1.

Detailed ways

The present invention will be described in further detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the content described.

Example 1: A method for preparing porous silicon/carbon/nano-metal composite anode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 4 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 24 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 50 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the plasma furnace current is 110A, the voltage is 140V, the argon pressure is 0.2MPa, and the silicon-carbon mixed powder The feed rate is 1g/min, and the organic impurities in the waste silicon powder will be directly taken out by the argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-AgNO ₃ -ethanol solution system and carry out the compounding of metal particles and nanoparticles at a temperature of 80°C for 4 hours, wherein the HF-AgNO ₃ -ethanol solution system contains HF The concentration is 0.5mol/L, the concentration of AgNO ₃ is 0.1mol/L, and the concentration of ethanol is 0.5mol/L; ultrasonic rinsing with deionized water until the washing liquid is neutral, and solid-liquid separation to obtain nano-metal particle composite silicon/carbon composite material , the nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain a porous silicon/carbon/nano-silver composite material (PSi/C/Nano-Ag composite material);

The scanning electron microscope (SEM) image of the original diamond wire-cut silicon waste is shown in Figure 1. From Figure 1, it can be seen that the particle size of the original diamond wire-cut silicon waste is uneven and the difference is huge. If it is directly applied to the negative electrode of a lithium-ion battery, it will , the negative electrode will produce a huge volume change in the process of deintercalating lithium, resulting in rapid capacity decay, and the negative electrode is damaged, causing the negative lithium-ion battery to fail rapidly during the cycle;

The scanning electron microscope (SEM) figure of pSi/C/Nano-Ag composite material is shown in Fig. 2, as can be seen from Fig. 2, nano-silver particles are evenly distributed on the surface of porous silicon particles, and the porous silicon/carbon/nano-metal composite anode material is composed of porous The porous structure formed by the accumulation of nano-spheres, and there are a large number of porous structures inside and between the spheres; the diffusion rate of lithium ions in the negative electrode material is greatly increased, and the porous structure in the spheres is caused by the deintercalation of lithium during charge and discharge. The volume expansion reserves a lot of space, which greatly eases the volume expansion;

The cycle performance curve of the original silicon waste and porous silicon/carbon/nano-silver composite material assembled into a half-cell at a rate of 0.5C is shown in Figure 3. The initial capacity of the original silicon waste negative electrode is 2970mAh/g, but after 20 cycles , its capacity is already less than 500mAh/g, the capacity decays extremely fast, and the initial coulombic efficiency is only 58%; the initial capacity of the porous silicon/carbon/nano-silver composite negative electrode is 2788mAh/g, which is only slightly lower than the original silicon waste negative electrode, After 50 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite negative electrode material is basically stable at 1250mAh/g, because the nano-silver ions in the porous silicon/carbon/nano-silver composite negative electrode can greatly improve the transmission of lithium ions .

Embodiment 2: A method for preparing porous silicon/carbon/nano-metal composite negative electrode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 4 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 18 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 60 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the plasma furnace current is 120A, the voltage is 130V, the argon pressure is 0.15MPa, and the silicon-carbon mixed powder The feed rate is 1.5g/min, and the organic impurities in the waste silicon powder will be directly taken out by the argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-Cu(NO ₃ ) ₂ -ethanol solution system and carry out metal particle nanoparticle compounding at a temperature of 40°C for 6 hours, wherein HF-Cu(NO ₃ ) ₂ -The concentration of HF in the ethanol solution system is 0.5mol/L, the concentration of Cu(NO ₃ ) ₂ is 0.2mol/L, and the concentration of ethanol is 0.5mol/L; use deionized water to ultrasonically rinse until the washing liquid is neutral, solid The nano-metal particle composite silicon/carbon composite material is obtained by liquid separation, and the nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain a porous silicon/carbon/nano-metal composite material (PSi/C/Nano-Cu composite material); The composite material was prepared as a silicon negative electrode half-cell, and after 50 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite negative electrode material was basically stable at 1200mAh/g.

Embodiment 3: A method for preparing porous silicon/carbon/nano-metal composite anode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 3 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 24 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 60 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the plasma furnace current is 120A, the voltage is 130V, the argon pressure is 0.15MPa, and the silicon-carbon mixed powder The feed rate is 2.0g/min, and the organic impurities in the waste silicon powder will be directly taken out by argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-Ni(NO ₃ ) ₂ -ethanol solution system and carry out metal particle nanoparticle compounding at a temperature of 80°C for 2 hours, wherein HF-Ni(NO ₃ ) ₂ -The concentration of HF in the ethanol solution system is 0.5mol/L, the concentration of Ni(NO ₃ ) ₂ is 0.2mol/L, and the concentration of ethanol is 0.5mol/L; use deionized water for ultrasonic rinsing until the washing liquid is neutral, solid The nano-metal particle composite silicon/carbon composite material is obtained by liquid separation, and the nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain a porous silicon/carbon/nano-metal composite material (PSi/C/Nano-Ni composite material); The composite material was prepared as a silicon negative electrode half-cell, and after 60 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite negative electrode material was basically stable at 1100mAh/g.

Embodiment 4: A method for preparing porous silicon/carbon/nano-metal composite negative electrode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 5 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 16 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 80 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the plasma furnace current is 120A, the voltage is 130V, the argon pressure is 0.15MPa, and the silicon-carbon mixed powder The feed rate is 2.0g/min, and the organic impurities in the waste silicon powder will be directly taken out by argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-Co(NO ₃ ) ₂ -ethanol solution system and carry out the compounding of metal particles and nanoparticles at a temperature of 60°C for 3 hours, wherein HF-Co(NO ₃ ) ₂ - the concentration of HF in the ethanol solution system is 0.5mol/L, the concentration of Co(NO ₃ ) ₂ is 0.2mol/L, and the concentration of ethanol is 0.5mol/L; use deionized water for ultrasonic rinsing until the washing liquid is neutral, solid The nano-metal particle composite silicon/carbon composite material is obtained by liquid separation, and the nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain a porous silicon/carbon/nano-metal composite material (PSi/C/Nano-Co composite material); The composite material was prepared as a silicon negative electrode half-cell, and after 50 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite negative electrode material was basically stable at 1180mAh/g.

Example 5: A method for preparing porous silicon/carbon/nano-metal composite anode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 6 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 12 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 90 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the current of plasma furnace is 110A, the voltage is 140V, the pressure of argon gas is 0.15MPa, and the silicon-carbon mixed powder The feed rate is 2.0g/min, and the organic impurities in the waste silicon powder will be directly taken out by argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-Al(NO ₃ ) ₃ -ethanol solution system and carry out metal particle nanoparticle compounding at a temperature of 60°C for 3 hours, wherein HF-Al(NO ₃ ) ₃ -The concentration of HF in the ethanol solution system is 0.5mol/L, the concentration of Al(NO ₃ ) ₃ is 0.15mol/L, and the concentration of ethanol is 0.5mol/L; use deionized water for ultrasonic rinsing until the washing liquid is neutral, solid The nano-metal particle composite silicon/carbon composite material is obtained by liquid separation, and the nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain a porous silicon/carbon/nano-metal composite material (PSi/C/Nano-Al composite material); The composite material was prepared as a silicon negative electrode half-cell, and after 40 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite negative electrode material was basically stable at 1150mAh/g.

Embodiment 6: A method for preparing porous silicon/carbon/nano-metal composite negative electrode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 4 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and the carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 24 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 90 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the current of plasma furnace is 110A, the voltage is 140V, the pressure of argon gas is 0.15MPa, and the silicon-carbon mixed powder The feed rate is 2.0g/min, and the organic impurities in the waste silicon powder will be directly taken out by argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-AgNO ₃ -Cu(NO ₃ ) ₂ -ethanol solution system and carry out the compounding of metal particles and nanoparticles at a temperature of 80°C for 4 hours, wherein the HF-AgNO In _{the 3} -Cu(NO ₃ ) ₂ -ethanol solution system, the concentration of HF is 0.5mol/L, the concentration of AgNO ₃ is 0.10mol/L, the concentration of Cu(NO ₃ ) ₂ is 0.05mol/L, and the concentration of ethanol is 0.5mol/L ; Ultrasonic rinsing with deionized water until the washing liquid is neutral, solid-liquid separation to obtain nano-metal particle composite silicon/carbon composite material, nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain porous silicon/carbon/nano Metal composite material (PSi/C/Nano-Ag@Cu composite material); the composite material is prepared as a silicon negative electrode half-cell, and after 50 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite negative electrode material is basically stable at 1100mAh/g.

Example 7: A method for preparing porous silicon/carbon/nano-metal composite anode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 4 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and the carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 24 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 80 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the current of plasma furnace is 110A, the voltage is 140V, the pressure of argon gas is 0.15MPa, and the silicon-carbon mixed powder The feed rate is 2.0g/min, and the organic impurities in the waste silicon powder will be directly taken out by argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-AgNO ₃ -Co(NO ₃ ) ₂ -ethanol solution system and carry out the compounding of metal particles and nanoparticles at a temperature of 80°C for 4 hours, wherein the HF-AgNO In _{the 3} -Co(NO ₃ ) ₂ -ethanol solution system, the concentration of HF is 0.5mol/L, the concentration of AgNO ₃ is 0.10mol/L, the concentration of Co(NO ₃ ) ₂ is 0.10mol/L, and the concentration of ethanol is 0.5mol/L ; Ultrasonic rinsing with deionized water until the washing liquid is neutral, solid-liquid separation to obtain nano-metal particle composite silicon/carbon composite material, nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain porous silicon/carbon/nano Metal composite material (PSi/C/Nano-Ag@Co composite material); the composite material is prepared as a silicon negative electrode half-cell, and after 40 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite negative electrode material is basically stable at 1150mAh/g.

Example 8: A method for preparing porous silicon/carbon/nano-metal composite anode material by cutting silicon waste through plasma activation, the specific steps are as follows:

(1) The diamond wire cutting silicon waste of photovoltaics is crushed, ground, and vacuum dried for 4 hours to obtain waste silicon powder;

(2) Mix the waste silicon powder and the carbon source in step (1) in a high-energy ball mill, pass through a 300-mesh sieve, and vacuum-dry for 24 hours to obtain a silicon-carbon mixed powder, wherein the mass fraction of the waste silicon powder in the silicon-carbon mixed powder is 70 %;

(3) Pass pure argon gas into the plasma furnace to remove the air in the furnace body, and use argon gas as the protective gas and carrier gas, and pass the silicon-carbon mixed powder in step (2) into the plasma furnace through the powder feeding device. Plasma activation treatment, gasification, condensation and recrystallization of silicon-carbon mixed powder to obtain nano-silicon/carbon composite material (PSi/C nano-composite material); among them, the current of plasma furnace is 110A, the voltage is 140V, the pressure of argon gas is 0.15MPa, and the silicon-carbon mixed powder The feed rate is 2.0g/min, and the organic impurities in the waste silicon powder will be directly taken out by argon gas in the form of gas to purify silicon due to the extremely low condensation temperature compared with silicon carbon;

(4) Place the nano-silicon/carbon composite material in step (3) in the HF-Co(NO ₃ ) ₂ -Cu(NO ₃ ) ₂ -Ni(NO ₃ ) ₂ -ethanol solution system at a temperature of 80°C Metal particles and nanoparticles were composited for 4 hours, in which the concentration of HF in the HF-Co(NO ₃ ) ₂ -Cu(NO ₃ ) ₂ -Ni(NO ₃ ) ₂ -ethanol solution system was 0.5mol/L, and the concentration of Co(NO ₃ ) ₂ 0.06mol/L, Cu(NO ₃ ) ₂ concentration 0.10mol/L, Ni(NO ₃ ) ₂ concentration 0.04mol/L, ethanol concentration 0.5mol/L; use deionized water to ultrasonically rinse until the washing liquid is Neutral, solid-liquid separation to obtain nano-metal particle composite silicon/carbon composite material, nano-metal particle composite silicon/carbon composite material is vacuum-dried and ground to obtain porous silicon/carbon/nano-metal composite material (PSi/C/Nano-Co @Cu@Ni composite material); the composite material was prepared as a silicon anode half-cell, and after 60 charge-discharge cycles, the capacity of the porous silicon/carbon/nano-silver composite anode material was basically stable at 1200mAh/g.

The above is a detailed description of the specific implementation of the present invention, but the present invention is not limited to the above-mentioned implementation, within the scope of knowledge of those of ordinary skill in the art, various modifications can be made without departing from the spirit of the present invention Variety.

Claims (6)

1. The method for preparing porous silicon/carbon/nano-metal composite negative electrode material by cutting silicon waste through plasma activation, is characterized in that, the specific steps are as follows: (1) Diamond wire cutting silicon waste is crushed, ground, and vacuum-dried to obtain waste silicon powder; (2) Mixing waste silicon powder and carbon source in step (1) evenly and vacuum drying to obtain silicon-carbon mixed powder; (3) Pass argon gas into the plasma furnace to get rid of the air in the furnace body, and use argon gas as protective gas and carrier gas, pass step (2) silicon-carbon mixed powder into the plasma furnace for plasma activation treatment, silicon Carbon mixed powder is gasified, condensed and recrystallized to obtain nano-silicon/carbon composite materials; (4) Place the nano-silicon/carbon composite material in step (3) in the HF-metal salt-alcohol solution system for compounding metal particles and nanoparticles, wash with deionized water, and separate solid-liquid to obtain nano-metal particle composite silicon/carbon Composite materials, nano-metal particle composite silicon/carbon composite materials are vacuum-dried and ground to obtain porous silicon/carbon/nano-metal composite materials; Step (2) The carbon source is glucose, fructose, sucrose, xylose, sorbose, citric acid, starch, polyethylene, polypropylene, cellulose, graphite, graphene, carbon nanotubes, aromatic hydrocarbons, aromatic lipids, One or more of petroleum asphalt or coal tar pitch; Step (3) The power of the plasma activation treatment is 10-150KW, the argon pressure is 0.10-0.70MPa, and the feed rate of the silicon-carbon mixed powder is 1-50g/min; The mass fraction of the waste silicon powder in the silicon-carbon mixed powder in step (2) is 3-90%. 2. according to the method for preparing porous silicon/carbon/nano-metal composite negative electrode material by plasma activation cutting silicon waste material described in claim 1, it is characterized in that: in the step (4) in the HF-metal salt-alcohol solution system, the HF concentration is 0.1 ～15mol/L, the metal salt concentration is 0.005～10mol/L, and the alcohol concentration is 0.1～20mol/L. 3. according to the method for preparing porous silicon/carbon/nano-metal composite anode material by plasma activation cutting silicon waste material according to claim 1, it is characterized in that: metal salt is silver salt, copper salt, cobalt salt, nickel salt, aluminum salt, titanium One or more of salts, and alcohols are one or more of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, propenyl alcohol, and vinyl alcohol. 4. according to the method for preparing porous silicon/carbon/nano-metal composite anode material by plasma activation cutting silicon waste material according to claim 3, it is characterized in that: silver salt is AgNO ₃ , Ag ₂ SO ₄ or Ag ₂ CO ₃ , copper salt is Cu(NO ₃ ) ₂ , CuSO ₄ or CuCO ₃ , the nickel salt is Ni(NO ₃ ) ₂ , NiSO ₄ or NiCO ₃ , the cobalt salt is Co(NO ₃ ) ₂ , and the aluminum salt is Al(NO ₃ ) ₃ . 5. according to the method for preparing porous silicon/carbon/nano-metal composite anode material according to the described plasma activation cutting silicon waste material of claim 1 or 2, it is characterized in that: HF-metal salt-alcohol solution system and nano-silicon/carbon composite material The liquid-solid ratio mL:g is (1-10):1. 6. According to claim 1 or 2, the method for preparing porous silicon/carbon/nano-metal composite anode material by cutting silicon waste by plasma activation, is characterized in that: the metal particle nanoparticle composite temperature is 20-80°C, and the time is 0.5-6h .

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