Exploring the electrochemical stability mechanism of a SnS2-based composite in dimethoxyethane electrolytes for potassium ion batteries

Abstract

Potassium-ion batteries (KIBs) have gained lots of attention due to their low price and performance, which is comparable to lithium-ion batteries. However, it is challenging for conventional carbon materials to achieve high performance in KIBs. As a kind of electrode material with a high specific capacity, metal chalcogenides have become a potential alternative. Nevertheless, the cycling stabilities of metal chalcogenides still suffer a dilemma due to the enormous expansion during the potassiation–depotassiation processes. In this work, we adopt dimethoxyethane (DME)-based electrolytes with a high K salt concentration to achieve stable cycling of SnS₂-containing composite in KIBs. After the optimization of the salt concentration in the DME-based electrolyte, our SnS₂-containing composite achieves an enhancement of the reversible specific capacity of 363 mA h g⁻¹ at 50 mA g⁻¹ after 50 cycles and delivers an improved rate performance with a reversible specific capacity of 359 mA h g⁻¹ at 1000 mA g⁻¹. To investigate the electrochemical enhancement mechanism, we analyze different K salt concentrations in the electrolytes and explore the electrode changes after cycles in different electrolytes. The results indicate that the decrease of free DME molecules in high salt concentration electrolytes leads to the suppression of the K-ion anisotropic aggregation during the potassiation–depotassiation processes, contributing to the homogeneous migration of the K-ion. In addition, the decrease of free DME molecules also causes a significant reduction of side reactions, which facilitates the enhancement of the cycling stability. Therefore, we believe our work will provide new insights into electrolyte engineering to further improve the electrochemical performance of metal chalcogenides for KIBs.