Experimental results indicated that transition metal borides VB2 and TiB2 electrodes can deliver exceptionally high discharge capacity of over 3100 and 1600 mAh/g, respectively, corresponding to an 11 and 6 electron oxidation reaction, although their parent elements V, Ti, and boron, are almost completely electrochemically inert. The reasons for the observed extraordinary capacities of diborides are probably due to the electrochemical activation of boron, which alleviates the passivation of the transition metal by clamping the electrode potential to a less positive range of potential. (C) 2004 The Electrochemical Society.