Trifluoroacetamide additive-driven solvation structure regulation and interfacial adsorption for wide-temperature...

Aqueous magnesium-air batteries (AMABs) are considered highly promising candidates for sustainable energy storage, but suffer from severe hydrogen evolution and chunk effect caused by uncontrolled Mg corrosion. Herein, we propose trifluoroacetamide (TFA) as a multifunctional electrolyte additive to address these challenges via dual solvation-interfacial regulation. Theoretical and experimental analyses reveal that TFA reconstructs the Mg²⁺ primary solvation sheath by replacing active H₂O molecules, weakening hydrogen-bond networks, and reducing free H₂O activity. Concurrently, TFA chemically adsorbs on Mg surfaces via electron-rich amide groups, forming a corrosion-resistant solid-electrolyte interphase (SEI) that suppresses the hydrogen evolution reaction (HER rate reduced by 57 %) and guides planar Mg stripping. The optimized 0.2 M TFA-containing electrolyte enables an ultrahigh Mg anode utilization efficiency of 70.6 % and extends the Mg-air batteries' lifespan to 145.61 h (2.3 × improvement) at 10 mA cm^-2. Remarkably, the TFA-enabled pure Mg system achieves a discharge voltage of 1.84 V, exceeding the highest value documented in existing literature, and delivers the pure Mg-based battery to achieve a power density of 2271.19 mWh·g^-1 at 10 mA·cm^-2. Simultaneously, TFA ensures stable operation of the battery under extreme environments of -20 °C and 50 °C, demonstrating exceptional wide-temperature adaptability. This work provides atomic-level insights into electrolyte engineering strategies for durable multivalent metal-air batteries.