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.