GeO₂-SnCoC composite anode material for lithium-ion batteries

Current methods for extending the cycle life of volume-expanded anode materials for lithium-ion batteries mainly focus on development of nanosize three-dimensional structures and composite materials. We propose a novel anode material of GeO₂-Sn₃₀Co₃₀C₄₀ that is synthesized by high energy ball milling (SPEX). This material depends on the nanosized and composite concept, which combines the advantageous properties of Sn-Co-C (long cycle life) and GeO₂ (high capacity). The composite anode shows a reversible capacity over 800 mAh/g with good capacity retention. Furthermore, the first-cycle Coulombic efficiency is 80%, much higher than the 34.6% obtained for pure GeO₂. Pair distribution function measurements indicated the reversible reaction of GeO₂ and SnO₂, which is the key factor in the improved Coulombic efficiency. This reversibility can be explained by the catalytic role of Co₃Ge₂ phase, which facilities the conversion reactions of metal oxides and acts as an electronic conductive component for the composite anode.