Study Of Tin Alloy Carbon Composite Used For Lithium Ion Battery

Sn emerged as a novel none carbonaceous anode material attracts more and more attention, because it has a high capacity of 990mAh/g and high working potential. But the bulk expansion of itself during the lithium intercalation and deintercalationgives it a short cycle life. Adding other elements to make an alloy or composite is a better way to prolong the cycle life. In this dissertation Sn/C and SnCo/C composite were synthesized by hydrothermal method and high temperature carbon reduction method on the basis of chemical reduction method, and their electrochemical performances were studied.Sn/C composite synthesized by the hydrothermal method shows about 700mAh/g lithium deintercalation capacity for the first time and 56% coulombic efficiency, and even after 300 cycles the capacity could reach 400mAh/g. The agglomeration of the Sn particles during the reduction process will be suppressed by the presence of O2 and complexing agent. Increasing the mass of glucose in the hydrothermal reaction will cause the capacity decline but a better cycle performance. Increasing the glucose concentration will improve the cycle performance when the same mass of the glucose is used. The increasing of the conducting agent ratio of the electrode will improve the cycle performance of the composite.SnCo/C composite synthesized by the hydrothermal method shows enhanced electric conductivity when Co was added, but too much Co will weaken the cycle performance. The increasing of the glucose concentration during the hydrothermal reaction will lead to the specific capacity decline, but no obvious cycle performance enhancement. The glucose concentration has little effect on the improvement of the cycle performance when the same mass of the glucose is used. The ingredient ratio of the electrode acts no effect on the cycle performance of the composite.SnCo(B)/C composite synthesized by high temperature carbon reduction method, has about 500mAh/g lithium deintercalation capacity for the first time and 65% coulombic efficiency, but shows poor cycle performance. Increasing the reacting temperature and time could entirety complete the reduction, but the Sn will melt out. The temperature raising speed shows little impact on the performances of the composite. Reduction could also be completely done under lower temperature but longer time. Heat treatment and ingredient ratio of the electrode act no effect on the performances of the composite.Heat treatment shows no impact on the electrochemical performances of acetylene black, but shows great impact on the electro performances of Sn/C composite and SnCo/C composite. Heat treatment can greatly enhance the cycle performance of Sn/C composite and SnCo/C composite. Heat treatment can be done in a very short time under high temperature. The protection atmosphere during the heat treatment has little impact on the Sn and Sn/C composite. Heat treatment enhancement functions only when it is done to the electrode.