It has been a puzzle that transition metals can unexpectedly react with lithium-based matrixes of LiF and Li2O in the potential versus Li/Li+ range from 0.01 to 3.5 V at room temperature. The electrochemical and theoretical investigations on the reactions of transition metals M (M=Co, Fe and Ni) with LiF and Li2O were carried out. The electrochemical reactivity of metal cobalt with LiF and Li2O has been examined by the discharge and charge, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. Density functional theoretical calculation results suggested that the stable compounds MLiF and MLi2O could be formed by the insertion of transition metal (M) in lithium-based matrixes with exothermic as an intermediate. The theoretical calculations provide an understanding in chemical reaction of M with LiF and Li2O. The small molecular or clusters reaction may play an important role in the electrochemical reaction of metal with transition Li2O or LiF, which could be used to explain for the unexpectedly reaction of transition metal with LiF and Li2O. (c) 2005 Elsevier Ltd. All rights reserved.