Phenolic Resin Carbon Coated Submicron Silicon Composite Material Lithium Storage Performance Research

Lithium-ion batteries have become the main powerful source for electric vehicles and personal portable devices due to their high energy density and long cycle life.As the third element in the earth's crust,Si has a low price and a theoretical capacity of 4200 m Ah·g^-1.It is considered the more promising anode material.However,the volume expansion of Si is too large,and the solid electrolyte interface which produced by contact between negative electrode material and electrolyte(SEI film)produced during charging and discharging increasingly consume lithium-ion batteries.In order to solve this problem,this article first uses high-energy ball milling to reduce the material particle size and corrodes it,and then coats a layer of phenolic resin pyrolytic carbon on the prepared submicron silicon to explore the structure and electrochemical performance of the silicon-carbon composite material.The results show that the electrical performance of the corroded silicon powder after ball milling is better than that of directly milled silicon powder.After ball milling,the median diameter of the material reached 0.237?m,and almost all the silicon particle size remained below 0.5?m,and the particle size became more uniform.After the corrosion treatment,the specific surface area of the material reached 131.35 m²·g^-1.When the current density is 200m A·g^-1,the first discharge specific capacity of raw material which treated with 20 hours of ball milling and 15%hydrofluoric acid mass fraction reaches 909 m Ah·g^-1,and it can still maintain123.6 m Ah·g^-1after 100 cycles,compared with the raw material silicon powder whose specific capacity has decayed to 28 m Ah·g^-1afer 5 cycles of discharge,it greatly improves the cycle performance.The electrochemical performance of the coating of ball milled and etched silicon powder is better than that of direct ball milled silicon powder coating.The electrochemical performance of the material is better when the mass fraction of phenolic resin accounts for 30%of the matrix and the reaction temperature is 800?.When the current density is 200 m A·g^-1,the first discharge specific capacity of carbon coated raw material which treated with 20 hours of ball milling is 4284.0 m Ah·g^-1,the second coulombic efficiency is 90.81%,the charge specific capacity after 75 cycles is 640 m Ah·g^-1,Coulomb efficiency remains above 98%.The paper has 31 pictures,5 tables,and 71 references.