Fully Active Bimetallic Phosphide Zn_0.5Ge_0.5P: A Novel High-Performance Anode for Na-Ion Batteries Coupled with Diglyme-Based Electrolyte

Abstract

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 Zn_0.5Ge_0.5P anode and its composite (Zn_0.5Ge_0.5P-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, Zn_0.5Ge_0.5P undergoes an alloying-type reaction, along with the generation of NaP, Na₃P, NaGe, and NaZn₁₃ 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^-1 and an ultrafast charge-discharge capability of 377.8 mAh g^-1 at 50C for 500 stable cycles were achieved within the Zn_0.5Ge_0.5P-C composite in a diglyme-based electrolyte. This work reveals the Na-storage reaction mechanism within Zn_0.5Ge_0.5P and offers a new perspective on designing high-performance anodes.