Abundant Cu₃P/Co₂P/CoP@NC Heterostructures Boost Charge Transfer Toward Fast and Durable Sodium Storage

ABSTRACT Heterogeneous structure and carbon coating are important ways to enhance the reaction kinetics and cycling stability of metal phosphides as anode materials for sodium‐ion batteries. Therefore, nitrogen‐doped carbon‐capped triphasic heterostructure Cu 3 P/Co 2 P/CoP@NC stands for nitrogen doped carbon nanorods were designed and synthesized through a combination of phosphide and carbonization. Kinetic analyses (cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique) and density functional theory calculations show that the three‐phase heterostructure and carbon layer effectively improve Na adsorption and migration as well as the electrochemical reactivity of the electrode. Based on this, Cu 3 P/Co 2 P/CoP@NC demonstrated excellent rate performance (305.9 mAh g −1 at 0.3 A g −1 and 202.8 mAh g −1 even at 10 A g −1 ) and cycling stability (the capacity decay rate is only 0.12% from the 5th to 300th cycle) when it is used for sodium‐ion battery anodes. The in situ X‐ray diffraction, ex situ X‐ray photoelectron spectroscopy, and high‐resolution transmission electron microscopy tests showed that Cu 3 P/Co 2 P/CoP@NC is based on a conversion reaction mechanism for sodium‐ion storage. In addition, the NVP@reduced graphene oxide (rGO)//Cu 3 P/Co 2 P/CoP@NC full‐cell delivers a high capacity of 210.2 mAh g −1 after 50 cycles at 0.3 A g −1 . This work can provide a reference for the design of high‐performance sodium electrode anode materials.