Phosphorus-Rich CuP2 Embedded in Carbon Matrix as a High-Performance Anode for Lithium-Ion Batteries

Phosphorus-rich CuP2 and its carbon composites have been investigated as an anode material for lithium-ion batteries. Through a facile, low-cost mechanochemical reaction, microsized composites composed of active CuP2 particles uniformly embedded in the carbon matrix have been successfully synthesized. Combined structural and electrochemical characterizations show that phosphorus-rich CuP2 undergoes irreversible reaction with lithium, giving metal-rich Cu3P and amorphous phosphorus at the end of the first cycle. Both Cu3P and phosphorus are reversibly formed in subsequent cycles, contributing to a high reversible capacity of >1000 mA h g-1. By controlling the carbon content, the electrochemical reversibility and stability of CuP2 are greatly improved. The carbon composite demonstrates a remarkable lithium-storage capability in terms of a stable capacity of >720 mA h g-1 over 100 cycles at 200 mA g-1, a high initial Coulombic efficiency of ∼83%, and a good rate capability with a capacity of >637 mA h g-1 at 1.6 A g-1. The performance improvement is mainly associated with the formation of the conductive carbon network that offers high conductivity and fast reaction kinetics, as well as enhanced structural stability of CuP2 anode.