Regulating Cu-F bonding force with cobalt phthalocyanine to boost the reversibility of CuF2 for endurable lithium-ion storage within moderate voltage-cutoff window

Abstract

CuF₂ is a promising candidate of electrode materials for lithium-ion batteries due to its high specific capacity, high power density and environmental friendliness. However, the irreversible phase conversion and sluggish kinetics caused by serious copper dissolution and low conductivity make CuF₂ difficult to achieve long cycling life. A facile strategy to incorporate CoPPc into CuF₂ was proposed firstly to regulate the Cu-F bonding force to realize the high reversibility of CuF₂ for lithium-ion storage. The results of DFT calculation, differential charge density simulation, work function calculation and COHP bond level calculation show that the existence of CoPPc can improve the surface charge distribution of CuF₂ and thus improve the reversibility for durable lithium-ion storage. The cycle life performance of the CuF₂@CoPPc composite electrode obtained by this method reached staggering 500 cycles and the capacity remained at 594.8 mAh/g.