Facilitating Synthesis of FeP/C@CoP Composites as High-Performance Anode Materials for Sodium-Ion Batteries

Low-cost, high-capacity sodium-ion batteries can help solve energy shortages and various environmental problems. Transition metal phosphides have a high theoretical capacity and a relatively low redox potential (vs. Na/Na+) and are therefore expected to be used as anodes for sodium-ion batteries. Herein, a heterostructure of a FeP/C@CoP composite with a robust structure, fast charge transfer and abundant active sites was rationally designed and synthesized by growing a Co-ZIFs nanoarray on Fe-MOFs and using a phosphiding process. Using this facilitated and cost-effective method, the FeP/CoP bimetal phosphide heterostructures were uniformly embedded into the carbon matrix, and the capacity and cycle stability were effectively improved. The specific capacity of the FeP/C@CoP was as high as 275.7 mA h g−1 at a high current density of 5 A g−1, and it was still as high as 321.9 mA h g−1 after 800 cycles at a current density of 1 A g−1. Cyclic voltammetry was used to perform the kinetic analysis, and it was determined that the FeP/C@CoP exhibited an obvious pseudocapacitive behavior during the charge–discharge process of up to 87.4% at a scan rate of 1 mv s−1. This work provides a facilitated method of synthesizing composites that can realize a viable strategy for high-performance energy storage.