Chloride‐Mediated Activation of Aluminum‐Alloyed Liquid Metal Anodes for Stretchable Asymmetric Energy Storage

ABSTRACT Gallium‐based liquid metals are attractive anodes for stretchable energy storage because they operate dendrite‐free, yet their bulk faradaic capacity remains locked behind a native oxide shell that conventional electrolytes cannot remove. Here, this passivation problem is resolved through the co‐design of an aluminum‐alloyed gallium–indium (AlGaIn) anode and a chloride‐rich water‐in‐ionic‐liquid (WIL) electrolyte, and the indium‐assisted electrochemical activation mechanism connecting them is identified. Al alloying converts the native oxide into a hydroxyl‐rich mixed Al–Ga–O shell susceptible to [GaCl 4 ] − ‐mediated etching, while the In(III) ions preferentially reduced into metallic patches that seed reversible Ga alloying/dealloying within the WIL. Potential‐resolved ex situ XPS indicates that in conventional TFSI‐based electrolytes, the electrode passivates beneath a TFSI‐derived interphase, whereas in the WIL, a chloride‐dominated electrode–electrolyte interphase forms instead. The activated anode gains 60% capacity during activation and retains ∼100% capacity over 1600 cycles at 500 mA g − 1 . Paired with a sonochemically derived GaOOH nanosheet cathode in a stretchable asymmetric cell, the asymmetric full cell delivers a maximum of 66.28 mWh cm −3 normalized to the active‐electrode volume, and 90% capacity retention over 4000 cycles. The halide‐mediated oxide‐displacement principle established here provides a generalizable electrolyte‐design strategy for oxide‐passivated liquid‐metal and post‐lithium anodes.