Structural Regulation of Oxygen Vacancy-Rich K_0.5 Mn₂ O₄ Cathode by Carbon Hybridization for Enhanced Zinc-Ion Energy Storage

High-voltage manganese-based materials are considered as promising cathode materials for aqueous zinc-ion batteries (AZIBs). Herein, oxygen vacancy-rich K_0.5 Mn₂ O₄ sheets were anchored uniformly onto honeycomb-like interconnected carbon nanoflakes (CNF@K_0.5 Mn₂ O₄ ) for AZIB cathode applications. In the composite, the CNFs provided excellent intergranular electron transport capability, while the oxygen vacancies enhanced the electron transport efficiency inside crystals, and the embedded K ions expanded the interlayer spacing and stabilized the layered crystal structure. A reversible specific capacity of 241 mAh g^-1 could be maintained by the composite at 0.5 A g^-1 for 400 cycles. A combination of ex-situ analytical methods and density functional theory calculations was carried out to elucidate the electrochemical mechanism of reversible zinc storage. In addition, flexible quasi-solid-state batteries of Zn//CNF@K_0.5 Mn₂ O₄ were constructed by substituting the traditional aqueous electrolyte for a quasi-solid-state gel electrolyte, which worked efficiently and exhibited high bending durability.