Harnessing interfacial wettability for durable magnesium storage in self-healing liquid GaBi alloy anodes

Magnesium-ion batteries (MIBs) are promising for next-generation energy storage, but conventional solid alloy-type anodes suffer from severe volume changes and rapid capacity decay. Liquid metal/alloy anodes represent a highly compelling solution, endowed with rapid electrochemical kinetics and intrinsic self-healing capabilities. Herein, we design a flexible, binder-free liquid GaBi alloy anode supported on a stainless steel mesh (ssm). To improve the inherently limited wettability of liquid GaBi on the substrate, a functional CuGa₂ interlayer is engineered via a combined sputtering and painting approach. Consequently, the integrated ssm-CuGa₂-GaBi electrode delivers outstanding Mg storage performance, achieving robust reversible capacities of 159.3/91.1 mAh g^-1 after 175/700 cycles at 200/500 mA g^-1, respectively. Crucially, operando X-ray diffraction (XRD) reveals that such remarkable Mg storage reversibility is driven by solid-liquid phase transitions, where Mg₃Bi₂, Mg₂Ga₅ and Mg₅Ga₂ form sequentially during discharge and undergo dealloying upon charge. Ultimately, this work not only deepens the mechanistic understanding of liquid MIB anodes but also provides an effective interfacial engineering strategy to enable their high performance.