Surface compatibility in a carbon-alloy composite and its influence on the electrochemical performance of Li/ion batteries

Carbon-alloy composites were prepared by coating carbon materials with different surfaces with Sn, Sb or SnSb. The SnSb-hard carbon spherule (HCS) composite electrode shows the best cycling performance. The matching of crystalline parameters between SnSb and the carbon ensures a good dispersion of SnSb alloy on the surface. The high density of the nucleation centers on the HCS surface leads to a small SnSb crystallite size. Open pores on the surface of HCS, into which the alloy crystals are allowed to grow, act as pinning centers, which further stabilize the composite. These three factors are supposed to be responsible for the best cyclic performance of SnSb-HCS composite. The latter two factors also result in a large BET surface area, which leads to a large initial irreversible capacity loss, because more solid electrolyte interface film is formed. It seems that the best cyclic performance and the highest initial efficiency are paradoxical in the SnSb-carbon composite. Further surface modification should be conducted to obtain better electrode materials.