Amorphous hollow carbon film as a flexible host for liquid Na-K alloy anode

Compared with solid alkali metal anodes (Li, Na, K), liquid metal anodes (LMAs) could enable high-energy batteries due to their unique advantages, such as self-healing property and no dendrites. Among LMAs, liquid Na-K alloy anode has become a hotspot due to its high theoretical capacity, low redox potential and formation at room temperature (RT). However, it is challenging to utilize liquid Na-K alloy directly and independently as an electrode; and the high surface tension makes it more difficult to immerse into porous current collectors at RT. Herein, an amorphous hollow carbon film (AHCF) consisting of hollow spheres with significant surface defects has been designed to quickly infiltrate Na-K liquid alloy into the hollow carbon film at RT, forming a composite electrode (Na-K@AHCF). The symmetric cell with Na-K@AHCF could exhibit a cycle lifespan up to 400 h at 0.1 mA/cm2 and achieve stable stripping/deposition even at 5 mA/cm2. When matching with cathode material of sulfurized polyacrylonitrile (SPAN), the obtained K-S full cell exhibits good cycle stability and rate performance.