Acidic-Neutral Decoupled Biphasic Electrolytes Enhance Deposition-Dissolution Chemistry in Zn–Mn Batteries

Aqueous Zn–Mn batteries are emerging as promising candidates for next-generation energy storage technologies owing to their advantages including high energy density, low cost, and excellent reliability. However, conventional aqueous electrolytes struggle to meet the dual deposition-dissolution requirements of the Mn2+/MnO2 cathodes and Zn2+/Zn anodes simultaneously. The Mn2+/MnO2 two-electron redox reaction in cathodes demands an acidic condition to achieve a theoretical capacity of 616 mAh g−1, twice that of neutral and alkaline systems, yet such a condition inevitably exacerbates Zn anode corrosion and undesirable hydrogen evolution reaction. To address this fundamental conflict, this study designs a self-stratifying aqueous-organic biphasic electrolyte, which successfully decouples the working conditions of the Mn cathodes and Zn anodes. The proof-of-concept Zn–Mn battery employing this biphasic electrolyte enables efficient Mn2+/MnO2 redox chemistry in the acidic aqueous phase and stable Zn plating-stripping in the neutral organic phase, therefore achieving a high discharge voltage of ~1.8 V, along with a stable cycling life of 90% capacity retention over 250 cycles. This work demonstrates an effective strategy for decoupling acidic and neutral conditions in a biphasic electrolyte and provides insights into the development of high-energy Zn–Mn batteries.