Hydroxyl‐Decorated Carbon Cloth with High Potassium Affinity Enables Stable Potassium Metal Anodes

Abstract Highly anticipated potassium metal batteries possess abundant potassium reserves and high theoretical capacity but currently suffer from poor cycling stability as a result of dendritic growth and volume expansion. Here, carbon cloths modified with different functional groups treated with ethylene glycol, ethanolamine, and ethylenediamine are designed as 3D hosts, exhibiting different wettability to molten potassium. Among them, the hydroxyl‐decorated carbon cloth with a high affinity for potassium can achieve molten potassium perfusion (K@EG‐CC) within 3 s. By efficiently inducing the uniform deposition of metal potassium, buffing its volume expansion, and lowering local current density, the developed K@EG‐CC anode alleviates the dendrite growth issue. The K@EG‐CC||K@EG‐CC symmetric battery can be cycled stably for 2100 h and has only a small voltage hysteresis of ≈93 mV at 0.5 mA cm −2 . Moreover, the high‐voltage plateau, high energy density, and long cycle life of K metal full batteries can be realized with a low‐cost KFeSO 4 F@carbon nanotube cathode. This study provides a simple strategy to promote the commercial applications of potassium metal batteries.