Deciphering the dynamic solid–liquid interphase for energetic high-mass-loading energy storage

Aqueous pseudocapacitive storage has shown promise for future energy applications, but it suffers from a single reaction pathway and mechanism that restrain performance breakthroughs, especially under commercial high-mass-loading conditions. Herein, using MnO₂ as a pseudocapacitive storage material, we tailored a reversible pseudocapacitive-type electrode/electrolyte interphase (PEI) by refining the cationic environment, which broke the limitation of MnO₂ to unlock an energetic dual-ion storage mechanism. Theoretical calculations demonstrated that the engineered dynamic PEI elevated the removal energy of active Mn species to stabilize dual-cation storage and, more importantly, provided highly available MnO₂/PEI heterointerface spaces to accommodate more charges. We unveiled that the exceptional heterointerface region with considerable charge redistribution enabled a significantly reduced ion-migration energy barrier compared with that of the pure MnO₂ interlayer, contributing to fast ‘‘multi-processing’’ storage of dual carriers. As a proof-of-concept, the tailored mechanism enabled robust stability with 92% capacitance retention after 25000 cycles. Besides, an appealing areal capacitance of 11.1 F cm^-2 was demonstrated under a high mass loading of 27.4 mg cm^-2. Our findings signify a paradigm shift in aqueous pseudocapacitive chemistry and offer insights into dynamic microenvironment regulation for building advanced energy storage devices.