Silicon-carbon negative electrode sheet using microporous carbon nanotube coating as carrier

Abstract

A silicon-carbon anode sheet using a microporous carbon nanotube coating as a carrier is employed. This coating serves as the carrier for vapor-phase deposited nano-silicon and amorphous carbon. The microporous carbon nanotube coating is pre-coated onto the surface of a copper foil or nickel-plated copper foil current collector. After high-temperature pyrolysis treatment, the coating's porosity is between 45% and 75%, its pore size (D90) is between 5 and 100 nanometers, and its single-sided thickness is between 3 and 15 micrometers. Before vapor-phase deposition of silicon and carbon, the coating's specific surface area is between 400 and 2200 m². 2 / g; Silicon-carbon anode sheet obtained after vapor deposition of silicon and carbon, with a specific surface area of ​​≤10m². 2 / g; the specific capacity of the silicon-carbon anode electrode coating is between 800-2400mAh / g; the diameter of the carbon nanotube raw material or carbon nanotube aggregate is between 2-50 nanometers, the length is ≥10 micrometers, the carbon content is ≥99.8%, Ig / Id≥20, and the weight ratio of the carbon nanotube raw material in the combined total of the main raw material carbon nanotube and the adhesive polymer is between 30-60wt.%.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, and in particular relates to silicon-carbon anode sheets used in lithium-ion batteries with high energy density characteristics. Background Technology

[0002] Currently, the clear industrial directions for improving the energy density of lithium-ion batteries include using silicon-carbon anode active material powder, lithium metal anode, or anode-free technology. Conventional silicon-carbon anode active material powder uses microporous carbon powder as a carrier for sequential CVD deposition of silicon and amorphous carbon. To improve the cycle life and power characteristics of lithium-ion batteries made from silicon-carbon anode active material powder, the pore size of conventional silicon-carbon anode active material powder is mostly controlled to be less than 3 nanometers. This usually requires chemical etching to create pores in the carbon powder. This method of manufacturing silicon-carbon anode active material powder usually uses silane gas, which has disadvantages such as high equipment investment, serious environmental impact, and insufficient production safety. When using traditional methods to manufacture silicon-carbon anode active material powder for subsequent use in lithium-ion battery manufacturing, it is necessary to mix and disperse it with artificial graphite powder to prepare a slurry for the anode, and then coat it on both sides of the copper foil current collector and roll it to form the anode sheet. The overall manufacturing cost is relatively high.

[0003] To overcome the shortcomings and deficiencies of existing technologies and products, this invention is proposed. Summary of the Invention

[0004] A silicon-carbon anode electrode with a microporous carbon nanotube coating as a carrier is characterized in that the silicon-carbon anode electrode uses a microporous carbon nanotube coating as a carrier for vapor-phase deposition of nano-silicon and amorphous carbon. The microporous carbon nanotube coating is pre-coated on the surface of a copper foil or nickel-plated copper foil current collector and then subjected to high-temperature pyrolysis treatment. After pyrolysis treatment, the porosity of the microporous carbon nanotube coating is between 45% and 75%, the pore size D90 is between 5 and 100 nanometers, and the single-sided thickness is between 3 and 15 micrometers. Before vapor-phase deposition of silicon and carbon, the specific surface area of ​​the microporous carbon nanotube coating is between 400 and 2200 m². 2 / g; Silicon-carbon anode sheet obtained by vapor deposition of silicon and carbon, with a specific surface area of ​​coating ≤10m². 2 / g; the specific capacity of the electrode coating is between 800-2400mAh / g; the diameter of the carbon nanotube raw material or carbon nanotube aggregate in the microporous carbon nanotube coating is between 2-50 nanometers, the length is ≥10 micrometers, the carbon content is ≥99.8%, Ig / Id≥20, and the weight ratio of carbon nanotube raw material in the total of the main raw material carbon nanotube and the adhesive polymer is between 30-60wt.%.

[0005] The silicon-carbon anode sheet uses a microporous carbon nanotube coating as a carrier, and the current collector is made of pure copper foil. The pure copper foil is rolled copper foil or electrolytic copper foil, the thickness of the copper foil is between 3-12 micrometers, and the copper content is ≥99.9%.

[0006] The silicon-carbon anode sheet with microporous carbon nanotube coating as carrier has a current collector made of nickel-plated copper foil. The copper foil substrate is made of rolled copper foil or electrolytic copper foil with a thickness of 3-10 micrometers and a copper content of ≥99.9%. The thickness of the nickel plating layer on one side is between 0.2-2 micrometers. The nickel plating is done by chemical plating of Ni-P or Ni-B, or by electroplating of pure Ni or NiCr alloy.

[0007] The method for manufacturing silicon-carbon anode sheets with microporous carbon nanotube coatings as carriers includes the following steps:

[0008] Step 1. Coat both sides of copper foil or nickel-plated copper foil with carbon nanotube coatings; after drying, the thickness of the coating on one side is between 4-18 micrometers.

[0009] Step 2. The composite strip semi-finished product processed in Step 1 is heated in stages at a temperature range of 100-700℃ under vacuum or inert atmosphere protection to thermally decompose the binder polymer in the carbon nanotube coating; the ratio of the residual carbon content after thermal decomposition of the binder polymer to the original weight of the binder polymer is ≤20%; the binder polymer is a water-soluble polymer, CMC, PEO, PVP, PAA, PEO-PPO, SBR emulsion, polyacrylate solution, etc., or a combination thereof, and pure water is used as the solvent when preparing the slurry.

[0010] Step 3. Take the semi-finished product processed in Step 2 above and perform roll-to-roll PVD physical vapor deposition of Si or Li-Si compound, or CVD vapor deposition of Si; then perform CVD vapor deposition of amorphous carbon film or PVD deposition of carbon film to directly obtain a negative electrode with high capacity characteristics. Detailed Implementation

[0011] To make the technical objectives, solutions, and advantages of this application clearer, a further detailed description is provided below in conjunction with embodiments.

[0012] Example 1

[0013] The silicon-carbon anode electrode uses a microporous carbon nanotube coating as a carrier. The microporous carbon nanotube coating is pre-coated onto the surface of a copper foil current collector electroplated with a nickel-chromium alloy layer, and then undergoes high-temperature pyrolysis treatment. After pyrolysis, the porosity of the microporous carbon nanotube coating is between 60-70%, the pore size D90 is between 30-60 nm, and the single-sided thickness is between 6-7 μm. Before vapor deposition of silicon and carbon, the specific surface area of ​​the microporous carbon nanotube coating is between 1200-1400 m². 2 / g; Silicon-carbon anode sheet obtained by vapor deposition of silicon and carbon, with a specific surface area of ​​coating ≤6m². 2 / g; the specific capacity of the electrode coating is between 1400-1600mAh / g; the carbon nanotube raw material of the microporous carbon nanotube coating is single-walled carbon nanotubes, and the diameter of the dispersed single-walled carbon nanotube aggregates is between 10-50 nanometers, the length is ≥20 micrometers, the carbon content is ≥99.8%, Ig / Id≥50, and the weight ratio of single-walled carbon nanotube raw material in the total of the main raw materials carbon nanotubes and adhesive polymers of the coating is 55wt.%.

[0014] The silicon-carbon anode sheet with microporous carbon nanotube coating as carrier has a current collector made of nickel-plated copper foil. The copper foil substrate is made of electrolytic copper foil with a thickness of 5 micrometers and a copper content of ≥99.9%. The thickness of the nickel-chromium alloy plating layer on one side is between 1 and 2 micrometers.

[0015] The method for manufacturing silicon-carbon anode sheets with microporous carbon nanotube coatings as carriers includes the following steps:

[0016] Step 1. Coat both sides of the nickel-plated copper foil with carbon nanotube coatings; after drying, the thickness of the coating on one side is between 8-9 micrometers.

[0017] Step 2. The composite strip semi-finished product processed in Step 1 is heated in stages at a temperature range of 100-700℃ under vacuum or inert atmosphere protection to thermally decompose the binder polymer in the carbon nanotube coating; the ratio of the residual carbon content after thermal decomposition of the binder polymer to the original weight of the binder polymer is ≤10%; the binder polymer is a combination of water-soluble polymers CMC and PVP, and pure water is used as the solvent when preparing the slurry;

[0018] Step 3. The semi-finished product processed in Step 2 above is subjected to roll-to-roll PVD physical vapor deposition of Si; then CVD vapor deposition of an amorphous carbon film layer is performed to directly obtain a negative electrode sheet with high capacity characteristics.

Claims

1. A silicon-carbon anode sheet with a microporous carbon nanotube coating as a carrier, characterized in that, The silicon-carbon anode electrode uses a microporous carbon nanotube coating as a carrier for vapor-deposited nano-silicon and amorphous carbon. The microporous carbon nanotube coating is pre-coated onto the surface of a copper foil or nickel-plated copper foil current collector and then subjected to high-temperature pyrolysis. After pyrolysis, the porosity of the microporous carbon nanotube coating is between 45% and 75%, the pore size D90 is between 5 and 100 nanometers, and the single-sided thickness is between 3 and 15 micrometers. Before vapor deposition of silicon and carbon, the specific surface area of ​​the microporous carbon nanotube coating is between 400 and 2200 m². 2 / g; Silicon-carbon anode sheet obtained by vapor deposition of silicon and carbon, with a specific surface area of ​​coating ≤10m². 2 / g; the specific capacity of the electrode coating is between 800-2400mAh / g; the diameter of the carbon nanotube raw material or carbon nanotube aggregate in the microporous carbon nanotube coating is between 2-50 nanometers, the length is ≥10 micrometers, the carbon content is ≥99.8%, Ig / Id≥20, and the weight ratio of carbon nanotube raw material in the total of the main raw material carbon nanotube and the adhesive polymer is between 30-60wt.%.

2. The silicon-carbon anode sheet with a microporous carbon nanotube coating as a carrier according to claim 1, characterized in that, The silicon-carbon anode sheet uses a microporous carbon nanotube coating as a carrier, and the current collector is made of pure copper foil. The pure copper foil is rolled copper foil or electrolytic copper foil, the thickness of the copper foil is between 3-12 micrometers, and the copper content is ≥99.9%.

3. The silicon-carbon anode sheet with a microporous carbon nanotube coating as a carrier according to claim 1, characterized in that, The silicon-carbon anode sheet with microporous carbon nanotube coating as carrier has a current collector made of nickel-plated copper foil. The copper foil substrate is made of rolled copper foil or electrolytic copper foil with a thickness of 3-10 micrometers and a copper content of ≥99.9%. The thickness of the nickel plating layer on one side is between 0.2-2 micrometers. The nickel plating is done by chemical plating of Ni-P or Ni-B, or by electroplating of pure Ni or NiCr alloy.

4. The silicon-carbon anode sheet with a microporous carbon nanotube coating as a carrier according to claim 1, characterized in that, The method for manufacturing silicon-carbon anode sheets with microporous carbon nanotube coatings as carriers includes the following steps: Step 1. Coat both sides of copper foil or nickel-plated copper foil with carbon nanotube coatings; after drying, the thickness of the coating on one side is between 4-18 micrometers. Step 2. The composite strip semi-finished product processed in Step 1 is heated in stages at a temperature range of 100-700℃ under vacuum or inert atmosphere protection to thermally decompose the binder polymer in the carbon nanotube coating; the ratio of the residual carbon content after thermal decomposition of the binder polymer to the original weight of the binder polymer is ≤20%. Step 3. Take the semi-finished product processed in Step 2 above and perform roll-to-roll PVD physical vapor deposition of Si or Li-Si compound, or CVD vapor deposition of Si; then perform CVD vapor deposition of amorphous carbon film or PVD deposition of carbon film to directly obtain a negative electrode with high capacity characteristics.