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 in-dependently 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. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

Compared with solid alkali metal anodes (Li, Na, K), liquid metal anodes (LMAs) have unique advantages such as self-healing property and no dendrites, enabling high-energy batteries. Among LMAs, liquid Na-K alloy anode has received attention due to its high theoretical capacity, low redox potential, and formation at room temperature. However, utilizing liquid Na-K alloy as an electrode is challenging, especially at room temperature with high surface tension. In this study, an amorphous hollow carbon film (AHCF) consisting of hollow spheres with significant surface defects was designed to quickly infiltrate Na-K liquid alloy at room temperature, forming a composite electrode (Na-K@AHCF). The Na-K@AHCF symmetric cell exhibited a cycle lifespan of up to 400 hours at 0.1 mA/cm2 and demonstrated stable stripping/deposition even at 5 mA/cm2. When combined with sulfurized polyacrylonitrile (SPAN) cathode material, the resulting K-S full cell showed good cycle stability and rate performance.