Solvent Modulation Strategy for Sb-Based Anode to Achieve Stable Potassium Storage

Abstract

Alloy-based materials are expected to be ideal anodes for potassium ion batteries (PIBs) due to their high reaction kinetics and high theoretical capacity. Unfortunately, the drastic volume expansion of alloy materials and the incompatibility between electrolytes, especially the formation of unstable solid electrolyte interphase (SEI), often lead to critical problems such as insufficient cycle life. Traditionally, high-concentration electrolytes (HCE) and localized high-concentration electrolytes (LHCE) can reduce the proportion of free anions and solvent molecules, forming a robust SEI to inhibit undesirable side reactions. However, the high cost limits the broad application prospect of alloy anode in large-scale energy storage systems. In this work, stable potassium storage in the alloy antimony (Sb) anode can be achieved using a simple electrolyte regulation strategy. The added ethylene carbonate (EC) can compete with 1,2-dimethoxyethane (DME) to obtain preferential coordination with K+ and generate a robust SEI for stable cycling by forming a more stable K+-EC solvent pair. The Sb@NC anode delivers a capacity of 376 mAh g-1 at a current density of 100 mA g-1 and remains stable over 100 cycles, achieving a capacity similar to that of HCE. The results show that the alloy electrode/electrolyte interface can be stabilized by changing the solvation environment of K+, which provides a new idea for the design of low-cost and high-stability electrolytes.

Keywords: potassium-ion batteries, Sb-based alloy electrode, solvation structure, Solid electrolyte interphase (SEI)