Solid Solution (Li_1.3-yCu_y)V₃O₈: Structure and Electrochemistry

Members of the (Li 1.3 - y Cu y )V 3 O 8 solid solution were synthesized for 0 < y < 1 by annealing, in evacuated sealed quartz ampules, stoichiometric mixtures of LiVO 3, Cu 2 O, and V 2 O 5, and their electrochemical performance in (Li 1.3 - y Cu y )V 3 O 8 /Li cells was studied as a function of y . The rationale for carrying out such a synthesis in a vacuum rather than in air, as commonly practiced, is given, and the origin of the Cu solid solution limit is explained on the basis of structural considerations. With the exception of the rate capability, the electrochemical performances of the (Li 1.3 - y Cu y )V 3 O 8 samples both in terms of capacity and capacity retention decreased with increasing y . The decrease in reversibility of the Li insertion/deinsertion process with increasing y is shown, through in situ X-rays and HRTEM measurements, to be nested in the partial reversibility of the Cu extrusion/re-injection process on cycling.