Core‐Shell Structured CoP@C Cubes as a Superior Anode for High‐Rate and Stable Sodium Storage

Abstract

AbstractTransition metal phosphides have emerged as a class of promising anode materials of sodium‐ion batteries owing to their excellent sodium storage capacity. However, the limited electronic conductivity and significant volume expansion have impeded their further advancement. In this work, we propose a rational design of cube‐like CoP @C composites with unique core‐shell structure via in situ phosphating and subsequent carbon coating processes. The uniform carbon coating serves as a physical buffering layer that effectively mitigates volume changes during charge/discharge processes, and prevents particle agglomeration and fragmentation, thereby enhancing the structural stability of electrode. Moreover, the nitrogen‐rich carbon layer not only provides additional active sites for sodium ion adsorption but also improves the electrode conductivity and accelerates charge transport dynamics. Consequently, the as‐synthesized CoP@C exhibits a remarkable capacity retention rate of 94.8 % after 100 cycles at 0.1 A g−1 and achieves a high reversible capacity of 146.7 mAh g−1 even under a high current density of 4.0 A g−1.