Aqueous magnesium batteries offer a promising alternative to lithium-ion technology due to their low cost, material abundance, safety, and comparable performance. However, magnesium metal anodes are hindered by passivation, and the narrow electrochemical stability window of aqueous electrolytes significantly limit the battery voltage. My research work introduces innovative aqueous electrolyte systems to address these challenges. A dual-electrolyte magnesium-air battery was developed, achieving a 50% higher peak power density and 46% higher open circuit voltage compared to traditional single-electrolyte systems. Subsequently, a novel water-in-salt electrolyte enabled the first rechargeable aqueous magnesium-ion battery with reversible magnesium metal anode stripping and plating behavior. Furthermore, a quasi-solid-state electrolyte was formulated to regulate ion storage at the cathode, delivering a voltage plateau of 2.6-2.0 V and a remarkable energy density of 264 Wh kg−1, nearly five times higher than current aqueous Mg-ion batteries. This work demonstrates significant advancements in aqueous magnesium batteries, offering a safe and high-performance energy storage solution for a clean energy future.