Shielding Mn3+ Disproportionation with Graphitic Carbon‐Interlayered Manganese Oxide Cathodes for Enhanced Aqueous Energy Storage System

Abstract

AbstractManganese dioxide (MnO2) materials have recently garnered attention as prospective high‐capacity cathodes, owing to their theoretical two‐electron redox reaction in charge storage processes. However, their practical application in aqueous energy storage systems faces a formidable challenge: the disproportionation of Mn3+ ions, leading to a significant reduction in their capacity. To address this limitation, the study presents a novel graphitic carbon interlayer‐engineered manganese oxide (CI‐MnOx) characterized by an open structure and abundant defects. This innovative material serves several essential functions for efficient aqueous energy storage. First, a graphitic carbon layer coats the MnOx molecular interlayer, effectively inhibiting Mn3+ disproportionation and substantially enhancing electrode conductivity. Second, the phase variation within MnOx generates numerous crystal defects, vacancies, and active sites, optimizing electron‐transfer capability. Third, the flexible carbon layer acts as a buffer, mitigating the volume expansion of MnOx during extended cycling. The synergistic effects of these features result in the CI‐MnOx exhibiting an impressive high capacity of 272 mAh g−1 (1224 F g−1) at 0.25 A g−1. Notably, the CI‐MnOx demonstrates zero capacity loss after 90 000 cycles (≈3011 h), an uncommon longevity for manganese oxide materials. Spectral characterizations reveal reversible cation intercalation and conversion reactions with multielectron transfer in a LiCl electrolyte.