Fully Active Bimetallic Phosphide ZnGeP: A Novel High-Performance Anode for Na-Ion Batteries Coupled with Diglyme-Based Electrolyte.

Metal phosphides are promising candidates for sodium-ion battery (SIB) anode owing to their large capacities with suitable redox potential, while the reversibility and rate performances are limited due to some electrochemically inactive transition-metal components and sluggish reaction kinetics. Here, we report a fully active bimetallic phosphide ZnGeP anode and its composite (ZnGeP-C) with excellent performance attributed to the Zn, Ge, and P components exerting their respective Na-storage merit in a cation-disordered structure. During Na insertion, ZnGeP undergoes an alloying-type reaction, along with the generation of NaP, NaP, NaGe, and NaZn phases, and the uniform distribution of these phases ensures the electrochemical reversibility during desodiation. Based on this reaction mechanism, excellent electrochemical properties such as a high reversible capacity of 595 mAh g and an ultrafast charge-discharge capability of 377.8 mAh g at 50C for 500 stable cycles were achieved within the ZnGeP-C composite in a diglyme-based electrolyte. This work reveals the Na-storage reaction mechanism within ZnGeP and offers a new perspective on designing high-performance anodes.