LiCo1-xMxPO4 (M = Mg2+, Mn2+ and Ni2+; 0 <= x <= 0.2) compounds have been synthesized by solid-state reaction method and studied as cathode materials for secondary lithium batteries. LiCoPO4 exhibits a discharge plateau at similar to 4.7 V with an initial discharge capacity of 125 mAh/g and on cycling capacity falls. Substitution of Co2+ with Mg2+/Mn2+/Ni2+ in LiCoPO4 has an influence on the initial discharge capacity and on cycling behaviour. The capacity retention of LiCoPO4 is improved by manganese substitution. Among the manganese substituted phases, LiCo0.95Mn0.05PO4 shows good reversible capacity of similar to 50 mAh/g. (C) 2005 Elsevier Ltd. All rights reserved.