Isocyanate Chemistry Enables a Stable Electrode-Electrolyte Interface for Potassium Metal Batteries

Potassium metal batteries (KMBs) have currently been regarded as one of the most promising energy storage devices for achieving high energy density. However, some inevitable challenges including high reactivity of metallic potassium, dendrite growth, and huge volume expansion impose a heavy burden on potassium metal batteries. Herein, an isocyanate molecule – 4-(trifluoromethoxy)phenyl isocyanate (TPI) is proposed to tailor the electrolyte solvation structure and interfacial chemistry in KMBs for the first time. The as-obtained electrolyte exhibits enhanced ionic conductivity, excellent electrode wettability and high exchange current density. Due to the energy levels difference, TPI preferentially accepts or donates electrons and undergoes redox reactions faster, thereby reducing the excessive decomposition of solvent molecules. Moreover, its inherent excellent film-forming property could form a protective layer at the electrode interface, effectively inhibiting the electrolyte decomposition and the adverse reactions caused by potassium metal. When assembled symmetrical batteries, at a current density of 0.5 mA cm⁻² and 0.5 mAh cm⁻², the electrolyte could stably run for more than 1400 h. The PTCDA||K full-cells could cycle 2000 times with good stability, and the Coulombic efficiency remained at approximately 99.84%. This strategy presents a promising pathway toward achieving performance metrics in KMBs.