Prolonged Electrochemical Cycling Characteristics of ZnSiP₂ Prepared with Mixed Crystalline-Amorphous Domains

Abstract

This paper presents an innovative approach wherein mechanical alloying and mechanical cation-disordering techniques are combined to synthesize peculiar zinc silicide phosphide (ZnSiP₂) anode materials under controlled atmosphere. In this method, Zn atoms and P atoms are simultaneously incorporated into the parent Si crystal structure, resulting in A(II)_xB(IV)_yP_x+y solid solutions with precise control over nanodomain structures of mixed crystalline-amorphous phases. This distinctive nanoarchitecture of the ZnSiP₂ anode, featuring an amorphous ionic-conduction phase network, facilitates the smooth transport of Li⁺ ions, thereby enabling an exceptionally prolonged electrochemical cycling performance, surpassing 200 cycles. In this study, we attempted to unravel the microstructure of ZnSiP₂ using transmission electron microscopy (TEM). It was observed that when synthesized under an inert Argon atmosphere, the material formed a polycrystalline structure consisting of numerous nanocrystals (5–10 nm) assembled. Additionally, when attempts were made to reduce synthesis costs by conducting the synthesis under ambient atmospheric (Air) conditions, amorphous regions were generated. This amorphous region within the polycrystalline ZnSiP₂ microstructure represents a novel finding. The electrochemical impedance measurements and galvanostatic intermittent titration technique (GITT) analysis conducted in this study not only revealed but also characterized the enhanced cycling performance of this unique ZnSiP₂ anode structure.