Hierarchical VS₂ Nanosheet Assemblies: A Universal Host Material for the Reversible Storage of Alkali Metal Ions

Abstract

Reversible electrochemical storage of alkali metal ions is the basis of many secondary batteries. Over years, various electrode materials are developed and optimized for a specific type of alkali metal ions (Li⁺ , Na⁺ , or K⁺ ), yet there are very few (if not none) candidates that can serve as a universal host material for all of them. Herein, a facile solvothermal method is developed to prepare VS₂ nanosheet assemblies. Individual nanosheets are featured with a few atomic layer thickness, and they are hierarchically arranged with minimized stacking. Electrochemical measurements show that VS₂ nanosheet assemblies enable the rapid and durable storage of Li⁺ , Na⁺ , or K⁺ ions. Most remarkably, the large reversible specific capacity and great cycling stability observed for both Na⁺ and K⁺ are extraordinary and superior to most existing electrode materials. The experimental results of this study are further supported by density functional theory calculations showing that the layered structure of VS₂ has large adsorption energy and low diffusion barriers for the intercalation of alkali metal ions.