Study on the insertion behaviors of Lithium-ions into CoFe3Sb12 based electrodes

The electrochemical properties of multiphase CoFe3Sb12 based materials were studied with lithium anode model cell Li|LiPF6 (EC+DMC) |CoFe3Sb12. A reversible capacity of about 490mAhg−1 (ca. 3430mAhcm−3) has been obtained in the first cycle. The reversible capacity keeps above 240mAhg−1 in the first 10 cycles. It was found that the cycle life and charge recovery are strongly dependent on particle size and conducting additive. The mechanism of lithium insertion into CoFe3Sb12 electrode was analyzed by ex situ XRD. It was found that there were two different types of the insertion reactions in the first discharge. One type is topotactic reaction and the other is reconstitution reaction. The chemical diffusion coefficient D̃Li versus lithium content x in CoFe3Sb12 has been examined by EIS for the first discharge.