Study On Carbon Coating Technology Of SiO_x Anode Material For Lithium Ion Batteries

Lithium-ion battery has become a new favorite in the new energy industry due to its green and environmental protection advantages.However,with the deepening of research on lithium-ion battery anode materials,the graphite anode,which is widely used now,is difficult to meet the needs of future development because of its theoretical specific capacity of 372 m Ah g^-1.Si O_x has become the focus of current research because of its high theoretical specific capacity and good cyclic stability,but Si O_x also has problems of poor electrical conductivity and volume expansion.Therefore,this paper focuses on the surface carbon coating modification technology,and realized the carbon coating on the surface of Si O_x through two different technical routes,dry coating and wet coating,and obtained Si O_x @C-dry,Si O_x @C-wet material with excellent electrochemical performance.The key process parameters in each technical route were explored and optimized,and the influences of dry and wet coating on the material structure and electrochemical properties were analyzed in detail.The research results are as follows:（1）Si O_x @C-dry material was successfully prepared by chemical vapor deposition using C₂H₂ as carbon source.The analysis results showed that the carbon layer formed on the surface of Si O_xby dry coating can effectively alleviates the volume expansion effect,improves the conductivity of the material,and make the material has good electrochemical performance.The Si O_x @C-dry material prepared at decomposition temperature of 800℃,vapor deposition time of 30 min,heating rate of 2℃min^-1,and gas flow rate of reaction gas,under the current density of 0.5C,after 150 cycles,The discharge capacity of Si O_xwas reduced to 577 m Ah g^-1,while that of Si O_x @C-dry was maintained at 1116.8 m Ah g^-1.In terms of magnification,under the current density of 0.1 C,0.2 C,0.5 C,1 C,2 C and 0.1 C,The discharge capacity of Si O_x@C-dry is 1438.91 m Ah g^-1,1361.72 m Ah g^-1,1250.19 m Ah g^-1,1127 m Ah g^-1,861.64 m Ah g^-1,1434.51 m Ah g^-1,The performance of Si O_x was better than that of Si O_xat each rate.（2）Spherical Si O_x@C-wet material was prepared by spray drying and high temperature pyrolysis using water-soluble phenolic resin as carbon source.On the surface of the analysis results,the carbon layer after wet spray drying and high temperature pyrolysis can not only alleviates the material volume expansion effect,improving the electrical conductivity,but also the spherical coating layer provides better structural strength for the whole particle,reduces the side reaction of the active material in the point solution,and improves the electrochemical performance of the material.When the heat treatment temperature is 900℃,the heat treatment time is 3h,the precursor material ratio is 10:9.For Si O_x @C-wet material prepared at a spray rate of 3 m L min^-1,the specific discharge capacity of Si O_xmaterial decreased to 577m Ah g^-1after 150 cycles at a current density of 0.5 C,while the specific discharge capacity of Si O_x@ C-wet was maintained at 1101.03 m Ah g^-1.The specific discharge capacity of Si O_x @C-wet under the current density of 0.1 C,0.2 C,0.5 C,1 C,2 C and 0.1 C were 1438.90 m Ah g^-1,1365.67 m Ah g^-1,1202.63 m Ah g^-1,958.91 m Ah g^-1,732.64 m Ah g^-1,1465.77 m Ah g^-1,This is a significant improvement over Si O_x raw material.