The electrochemical properties of multiphase CoFe3Sb12 based materials were studied with lithium anode model cell LilLiPF(6) (EC + DMC) \ CoFe3Sb12. A reversible capacity of about 490 mA h g(-1) (ca. 3430 mA h cm(-3)) has been obtained in the first cycle. The reversible capacity keeps above 240 mA h g(-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 (D) over bar (Li) versus lithium content x in CoFe3Sb12 has been examined by EIS for the first discharge. (C) 2001 Elsevier Science B.V. All rights reserved.