CoPSe: A New Ternary Anode Material for Stable and High-Rate Sodium/Potassium-Ion Batteries

The exploration of ideal electrode materials overcoming the critical problems of large electrode volume changes and sluggish redox kinetics induced by large ionic radius of Na+/K+ ions is highly desirable for sodium/potassium-ion batteries (SIBs/PIBs) toward large-scale applications. The present work demonstrates that single-phase ternary cobalt phosphoselenide (CoPSe) in the form of nanoparticles embedded in a layered metal-organic framework (MOF)-derived N-doped carbon matrix (CoPSe/NC) represents an ultrastable and high-rate anode material for SIBs/PIBs. The CoPSe/NC is fabricated by using the MOF as both a template and precursor, coupled with in situ synchronous phosphorization/selenization reactions. The CoPSe anode holds a set of intrinsic merits such as lower mechanical stress, enhanced reaction kinetics, as well as higher theoretical capacity and lower discharge voltage relative to its counterpart of CoSe2, and suppressed shuttle effect with higher intrinsic electrical conductivity relative to CoPS. The involved mechanisms are evidenced by substantial characterizations and density functional theory (DFT) calculations. Consequently, the CoPSe/NC anode shows an outstanding long-cycle stability and rate performance for SIBs and PIBs. Moreover, the CoPSe/NC-based Na-ion full cell can achieve a higher energy density of 274 Wh kg(-1), surpassing that based on CoSe2/NC and most state-of-the-art Na-ion full cells based on P-, Se-, or S-containing binary/ternary anodes to date.

Automated summary

The CoPSe/NC material prepared in this study is an excellent anode material for sodium/potassium-ion batteries, with ultra stability and high rate characteristics, higher theoretical capacity and lower discharge voltage compared to CoSe2. Its outstanding performance is verified through a series of characterizations and calculations.