Characterization and Electrochemical Properties of Li2Cu0.5Ni0.4M0.1O2 Lithium-ion Battery Cathodes

Abstract

Doped lithium copper-nickel mixed-metal oxides are prepared and studied as cathode materials for secondary Li-ion batteries. The compounds, Li2Cu0.5Ni0.4M0.1O2 (where M = Al, Ga), are made using solid state and micro-emulsion synthesis techniques. All compounds have a body-centered orthorhombic (Immm) crystal structure. The undoped compound has an initial discharge capacity of 270 mAh/g but exhibits poor capacity retention with cycling. The Al- and Ga-doped compounds made by solid-state synthesis have a higher discharge capacity than those made by micro-emulsion. Micro-emulsion processed compounds exhibit better cycleability and capacity retention upon charge/discharge suggesting a more stable crystal structure. Gallium doping improved the structural stability resulting in lowered irreversible capacity loss. Two reversible reaction mechanisms, lithium intercalation/de-intercalation and a displacement reaction are suggested to occur in the Li2Cu0.5Ni0.4M0.1O2 system.