Electrochemical lithiation of Co2MnSi with a Heusler structure is investigated as a candidate negative electrode (anode) material for secondary lithium batteries. The electrode maintains a reversible discharge capacity of 112 mAh g(-1) for 50 cycles when cycled between 0.01 and 3 V. It is proposed that the lithiation mechanism consists of two steps, Co2MnSi transforms to Heusler-type Li-2 MnSi during the first charge cycle and subsequent charge-discharge cycles involve the formation of a solid Solution in LixMnSi. The latter compound maintains its structural integrity throughout cycling to provide steady cycling behaviour. Magnetic measurements are also employed to Substantiate further the structural changes during electrochemical cycling. (C) 2008 Elsevier B.V. All rights reserved.