Isotope interface design for high-energy aqueous proton batteries

The stability of the electrode-electrolyte interface is crucial for the long-term operation of battery chemistries, particularly under harsh conditions with corrosive acidic/alkaline aqueous electrolytes. Here, we report the design of a H₂¹⁸O-H₂¹⁶O isotope interface to promote the formation of a protective electrode-electrolyte interphase, as demonstrated by a model investigation based on an aqueous proton battery (APB) utilizing strongly acidic aqueous electrolytes. This design enables the manganese-iron Prussian blue analog (MnFe-PBA), typically considered acid intolerant, to cycle stably over 10,000 cycles in corrosive H₃PO₄ electrolytes. This acid resistance is attributed to the isotope interface-governed in situ formation of interphases comprising hydrogen-bonded frameworks. With the high-energy MnFe-PBA cathode, the full battery attains a high voltage plateau (⁓1.2 V) and energy density (77.6 Wh kg⁻¹), both surpassing all previously reported APBs. Our findings provide a novel approach for enhancing the performance of aqueous batteries subject to extremely corrosive conditions and encourage the integration of isotopic science with battery technology.