Unusual Melting Trend in an Alkali Asymmetric Sulfonamide Salt Series: Single-Crystal Analysis and Modeling

Designing High-Donicity Anions for Rechargeable Potassium Superoxide/Peroxide Batteries

A battery cathode based on the superoxide/peroxide redox not only inherits the advantage of oxygen (O₂ ) batteries in high capacities and low costs but also overcomes the disadvantages in O₂ storage, electrolyte evaporation, and anode deactivation due to O₂ crossover. Herein, we report an enhanced potassium superoxide (KO₂ )/peroxide (K₂ O₂ ) conversion by adopting a high-donicity anion additive in the ether-based electrolyte. Such an anion was synthesized via a "Solvent-in-Anion" strategy and validated to enhance the electron donicity of the electrolyte. The use of high-donicity anion could lead to enhanced KO₂ utilization (≈90.2 %) by retarding electrode passivation and allow the full charging back of K₂ O₂ through the solution-mediated pathway without electrocatalysts. No apparent cell degradation is observed during the first 120 cycles by controlling the reversible depth-of-discharge capacity at 292 mAh g^-1 KO 2 ${{_{{\rm KO}{_{2}}}}}$ within an O₂ -free region. The K-KO₂ cell delivers a high energy efficiency (>84.4 %) and a lifespan of over 1440 hours.