Building K-C anode with ultrahigh self-diffusion coefficient for solid state potassium metal batteries operating at -20 to 120°C.

Solid state potassium metal batteries are intriguing in grid-scale energy storage, benefiting from the low cost, safety and high energy density. However, their practical applications are impeded by poor K/solid electrolyte (SE) interfacial contact and limited capacity caused by the low K self-diffusion coefficient, dendrite growth, and the intrinsically low melting point/soft features of metallic K. Herein, we demonstrate that a fused-modeling strategy using potassiophilic carbon allotropes molted with K, can enhance the electrochemical performance/stability of the system via promoting K diffusion kinetics (2.37 × 10 -8 cm 2 s -1 ), creating an extremely low interfacial resistance (∼1.3 Ω cm 2 ), suppressing dendrite growth, and maintaining mechanical/thermal stability at 200°C. A homogeneous/stable K stripping/plating is consequently implemented with a high current density of 2.8 mA cm -2 (at 25°C) and a record-high areal capacity of 11.86 mAh cm -2 (at 0.2 mA cm -2 ). The enhanced K diffusion kinetics contributes to sustaining intimate interfacial contact, stabilizing the stripping/plating at high current densities. Full cells coupling ultrathin K-C composite anodes (∼50 μm) with Prussian blue cathodes and β/β"-Al 2 O 3 SEs delivers a high energy density of 389 Wh kg -1 with a retention of 94.4% after 150 cycles and fantastic performances in a temperature range from -20 to 120°C. This article is protected by copyright. All rights reserved.