Influence of isovalent ion substitution on the electrochemical performance of LiCoPO4

LiCo{sub 1-x}M {sub x}PO{sub 4} (M = Mg{sup 2+}, Mn{sup 2+} and Ni{sup 2+}; 0 {<=} x {<=} 0.2) compounds have been synthesized by solid-state reaction method and studied as cathode materials for secondary lithium batteries. LiCoPO{sub 4} exhibits a discharge plateau at {approx}4.7 V with an initial discharge capacity of 125 mAh/g and on cycling capacity falls. Substitution of Co{sup 2+} with Mg{sup 2+}/Mn{sup 2+}/Ni{sup 2+} in LiCoPO{sub 4} has an influence on the initial discharge capacity and on cycling behaviour. The capacity retention of LiCoPO{sub 4} is improved by manganese substitution. Among the manganese substituted phases, LiCo{sub 0.95}Mn{sub 0.05}PO{sub 4} shows good reversible capacity of {approx}50 mAh/g.