2LiH+M (M = Mg, Ti): New concept of negative electrode for rechargeable lithium-ion batteries

xLiH + M composites, where M = Mg or Ti, are suggested as new candidates for negative electrode for Li-ion batteries. For this purpose, the xLiH + M electrode is prepared using the mechanochemical reaction: MHx + xLi -> xLiH + M or by simply grinding a xLi H + M mixture. The most promising electrochemical behaviour is obtained with the (2LiH + Mg) composite prepared via a mechanochemical reaction between MgH2 and metallic Li leading to a very divided composite in which Mg crystallites of 20 nm size are embedded in a LiH matrix. Reversible capacities of 1064 mAh g(-1) (three times as much as the one of graphite) and 600 mAh g(-1) are reached for these phase mixtures after 1 and 28 h of grinding in vertical and planetary mill, respectively. The (2LiH + Ti) mixture prepared via the mechanochemical reaction between TiH2 and Li exhibits a reversible capacity of 428 mAh g(-1). From X-ray diffraction measurements. the performances of the electrodes are attributed to the electrochemical conversion reaction: M + xLiH <-> MHx + xLi(+) + xe(-) (M = Mg, Ti) followed for M = Mg by an alloying process where M reacts with lithium ions to form Mg1-xLix alloys. (C) 2009 Elsevier B.V. All rights reserved.