Structural and electrochemical properties of micro- and nano-crystalline CoSn electrode materials.

Nanocrystalline CoSn with an average crystallite size of 19 nm is obtained at 265 degrees C by following a one-pot method. The structural and electrochemical properties of nano-CoSn are compared to those of micro-CoSn (319 nm) obtained at 500 degrees C. Micro-CoSn has specific capacities below 100 mAhg(-1), but very stable cycling behavior. In contrast, nano-CoSn exhibits reversible specific capacities of over ca. 400 mAhg(-1)in the first cycles, depending on the cycling conditions. The crystalline structure of micro-CoSn is preserved after electrochemical reaction with lithium. Nano-CoSn becomes amorphous upon cycling and a modified 119Sn Mössbauer spectrum corresponding to a LiCoSn nano-alloy is observed.