Toward High-Safety Potassium-Sulfur Batteries Using a Potassium Polysulfide Catholyte and Metal-Free Anode

Abstract

Based on the reversible conversion reactions, K2Sx (S <= x <= 6) ->(discharge) K2S3 ->(charge) K2S5, discharge charge the proposed K-S battery delivered a high discharge capacity of similar to 400 mAh g(-1) at 0.1 C -rate with stable cycle retention (94% after 20 cycles) and good rate capability up to 2 C -rate. In addition, instead of an explosive and highly reactive potassium metal electrode, a full cell consisting of an electrochemically potassium -impregnated hard carbon and the K2Sx (5 <= x <= 6) catholyte was constructed to demonstrate the feasibility of a safe K S battery system free of metallic potassium.