Preparation And Electrochemical Performances Of Silicon Carbon Anode Materials With The Void Structure

With more and more mature applications of new energy and power systems,lithium-ion batteries（LIBs）are bound to play an important role in the future.However,commercial graphite anode can no longer meet the pursuit of long mileage range due to their low theoretical specific capacity.Silicon anode are considered to be a new generation of anode materials to alleviate the range anxiety in the electric vehicle（EV）industry because of their merits,which include a high theoretical specific capacity and low working potential.In view of the problems of large volume expansion and poor electrical conductivity in practical applications,silicon anode materials are usually combined with carbon materials to improve the electrochemical reversibility and cycling stability.Therefore,in this paper,Si/C anode materials are mainly modified from structural control.Two Si/C composites with different void structures are prepared and the influence of their structure and composition on the lithium storage properties are systematically investigated.The details of the study are as follows:（1）The Si@void@C electrode with extremely high silicon content is prepared by atomic layer deposition technology,traditional chemical polymerization,subsequent annealing and etching processes.Where the Al₂O₃ template is a unique dual functional template that can synchronously control the thickness of the carbon coating layer and the size of the nano void.The effect of different template sizes on the lithium storage performance of Si/C composites is emphatically investigated.The results show that when the template size is 14 nm,Si@void@C100 sample exhibits excellent electrochemical performance.After 100 cycles at a current density of 200 mAg^-1,the specific capacity of Si@void@C-100 is 1694.6 mAh g^-1,and the capacity retention rate is 65.6%.（2）The free-standing Si@void@CNFs electrode is prepared by electrospinning and subsequent annealing treatment.Where the sulfur template is a functional template that can construct the void structure.The effect of void structure on the lithium storage performance of Si/C composites is emphatically investigated.The results show that the Si@void@CNFs composite have excellent electrochemical properties.After 100 cycles at a current density of 200 mAg^-1,the specific capacity is 1366.3 mAh g^-1,and the capacity retention rate is 75.8%.After 500 cycles at a high current density of 1Ag^-1,the specific capacity can arrive at 593.5 mAhg^-1.