Alkali‐Ion Batteries by Carbon Encapsulation of Liquid Metal Anode

Abstract Gallium‐based metallic liquids, exhibiting high theoretical capacity, are considered a promising anode material for room‐temperature liquid metal alkali‐ion batteries. However, electrochemical performances, especially the cyclic stability, of the liquid metal anode for alkali‐ion batteries are strongly limited because of the volume expansion and unstable solid electrolyte interphase film of liquid metal. Here, the bottleneck problem is resolved by designing carbon encapsulation on gallium–indium liquid metal nanoparticles (EGaIn@C LMNPs). A superior cycling stability (644 mAh g⁻¹ after 800 cycles at 1.0 A g⁻¹) is demonstrated for lithium‐ion batteries, and excellent cycle stability (87 mAh g⁻¹ after 2500 cycles at 1.0 A g⁻¹) is achieved for sodium‐ion batteries by carbon encapsulation of the liquid metal anode. Morphological and phase changes of EGaIn@C LMNPs during the electrochemical reaction process are revealed by in situ transmission electron microscopy measurements in real‐time. The origin for the excellent performance is uncovered, that is the EGaIn@C core–shell structure effectively suppresses the non‐uniform volume expansion of LMNPs from ≈160% to 127%, improves the electrical conductivity of the LMNPs, and exhibits superior electrochemical kinetics and a self‐healing phenomenon. This work paves the way for the applications of room‐temperature liquid metal anodes for high‐performance alkali‐ion batteries.