Cobalt–Copper Bimetallic Phosphide/Carbon Nanocomposites Derived from Metal–Organic Frameworks for Sodium-Ion Batteries

Transition metal phosphides have attracted attention in the field of energy storage due to their high theoretical capacity. Nevertheless, challenges such as inadequate electrical conductivity, expansion in volume, and ion clustering during charging and discharging events contribute to diminished cycling durability and rapid capacity deterioration, thereby constraining their real-life utilization. In this study, Co–Cu bimetallic phosphide/carbon nanocomposites (CoCuP@C-X) are obtained by the one-step phosphide/carbonization of metal–organic framework precursors through high-temperature calcination in response to these challenges. The incorporation of the Cu element enhances the electrical conductivity, while the carbon coating mitigates the volumetric expansion and avoids the aggregation of nanoparticles. CoCuP@C-2, utilized as a sodium-ion battery (SIB) anode, maintains relatively good cyclic stability, showing a discharge specific capacity of 415 mAh g–1 at a current density of 1 A g–1. Meanwhile, the transformation mechanism from the CoP phase to the Co and Na3P phases is explored using ex situ X-ray diffraction analysis. These findings suggest that the CoCuP@C-X nanocomposite material has considerable potential as an anode material for SIBs.