High-Energy and Long-Lifespan Potassium-Sulfur Batteries Enabled by Concentrated Electrolyte

Abstract

Potassium-sulfur (K-S) batteries are emerging as low-cost and high-capacity energy-storage technology. However, conventional K-S batteries suffer from two critical issues that have not yet been successfully resolved: the dissolution of potassium polysulfides (KPS) into the liquid electrolyte and the formation of K dendrites on the K metal anode, which lead to inadequate cycling efficiencies with a low reversible capacity. Herein, a high-capacity and long cycle-life K-S battery consisting of a highly concentrated electrolyte (HCE) (4.34 mol kg(-1) potassium bis(fluorosulfonyl)imide in a 1,2-Dimethoxyethane) and a sulfurized polyacrylonitrile (SPAN) cathode is presented The application of a HCE efficiently suppresses the dendritic growth of K, as evidenced by operando optical imaging and phase field modeling, owing to the reduced K-ion depletion on the electrode surface and a uniform Faradaic current density over the K metal anode surface. Additionally, because S is covalently bonded to the C backbone of PAN in the SPAN structure, the SPAN cathode inhibits the dissolution of KPS. These features generate synergy that the proposed K-S battery can provide a practical areal capacity of 2.5 mAh cm(-2) and unprecedented lifetimes with high Coulombic efficiencies over 700 cycles.