Exploring the Li-Ga room temperature phase diagram and the electrochemical performances of the LixGay alloys vs. Li

Li2Ga7, LiGa, and Li2Ga alloys were synthesized by ball-milling, from Li powders and Ga ingots, and characterized for their structural and electrochemical performances. Special attention was devoted to the Li-driven 3D(LiGa) --> 2D(Li2Ga) transformation that occurs at 0.02 V vs. Li+/Li on discharge. By in situ X-ray measurements we demonstrated that such a transition, accompanied by a 60% volume change, is initially nicely reversible, but rapidly becomes detrimental to the cell capacity retention upon cycling. Bypassing the (LiGa) --> (Li2Ga) transition was shown to considerably increase our cell performances, with capacity retention curves levelling at 300 mA h/g for at least 20 cycles. (C) 2004 Published by Elsevier B.V.