Liquid eutectic gallium–indium as a magnesium-ion battery anode with ultralong cycle life enabled by liquid–solid phase transformation during (de)magnesiation at room temperature

Abstract

Mg-ion batteries represent a promising alternative to Li-ion batteries but face challenges with Mg dendrite formation on Mg metal anodes. Conventional solid alloy anodes prevent Mg dendrite formation but are prone to failure due to significant volume changes during (de)magnesiation. “Self-healing” electrodes composed of liquid alloys can undergo reversible liquid–solid phase transformations during (de)magnesiation, thereby “healing” themselves from the volume expansion-induced material degradation, offering a promising solution. Here, we employ a liquid eutectic Ga–In alloy as a conceptual “self-healing” Mg-ion battery anode with a 246 mA h g_GaIn⁻¹ theoretical capacity. This anode demonstrates an unprecedented cycle life of 2000 cycles at the C-rate of 1C, retaining 91% capacity (225 mA h g⁻¹ post-cycled capacity) at 25 °C. We elucidate the morphology evolution and storage mechanism during (de)magnesiation using in situ wide-angle X-ray scattering and cryogenic focused ion beam scanning electron microscopy. These results pave the way for developing high-performance electrodes for next-generation Mg-ion batteries.