Abstract:

The SnCo_1-xFe_x/C (x=0.1, 0.2, 0.3, 0.4) composites as novel anode materials for lithium-ion batteries with large capacity were prepared by ball milling first and then solid-state sintering. The influences of the partial substitution of inert metal Fe for Co on material structures and the electrochemical properties were investigated. Structure analyses show that the uniform solid dissolution of Fe into CoSn phase promotes the formation of CoSn₂ impurity phase. With the growth of x, the cell volumes of CoSn phase is enlarged, the grain size decreases and the content of CoSn₂ increases. Carbon black is mainly physically mixed with other phases on the surface of particles. Electrochemical analyses reveal that the reversible capacity and cycle performance are both improved through the introduction of Fe. When x is 0.2, the cycle performance is up to the maximum, 85.1% of the reversible capacity after 50 cycles. During cycling, among SnCo/C, SnCo_0:8Fe_0.2 /C and SnCo _0:6 Fe _0:4 /C samples, the grain size of CoSn phase for SnCo_0:8Fe_0:2/C sample increases leastly. It is usually believed that the comprehensive effects of grain size, structure stability and impurity-phase content lead to the maximum of the cycle performance at appropriate content of Fe (x=0.2).

Key words: Lithium-ion batteries, SnCo/C, Fe, Cycle performance, Grain refinement