Ambient-temperature aging-driven oxygen vacancy engineering of α-MnO2/GO for near-theoretical lithium storage

초록

Oxygen vacancy engineering has emerged as a powerful strategy to enhance the electrochemical performance of transition metal oxides; however, achieving high defect density without compromising structural stability remains a fundamental challenge. Herein, we report an ambient-temperature, aging-driven defect engineering strategy that enables the formation of oxygen-vacancy-rich alpha-MnO2 nanoparticles uniformly anchored on graphene, which delivers a near-theoretical lithium storage capacity with superior cycling durability. Prolonged aging induced continuous secondary reactions that promote the structure evolution of oxygen-vacancy-enriched alpha-MnO2, as confirmed by EPR and XPS analyses. The resulting defect-rich MnO2 exhibited enhanced intrinsic electronic conductivity and accelerated lithium-ion kinetics, resulting in a high reversible capacity of 1175 mAh g-1 at 0.1 A g-1, approaching the theoretical limit. Furthermore, a mild low-temperature heat treatment (95 degrees C) successfully activated the MnO2/graphene interface via Mn-O-C configuration while preserving oxygen vacancies, leading to accelerated interfacial charge transfer and outstanding cycling stability. Notably, the optimized composite exhibited sustained activation behavior, with capacity increasing to 977 mAh g-1 over 400 cycles. This work highlights a scalable and energy-efficient route for interfacial defect engineering in metal oxide/graphene systems, providing a general strategy to achieve high defect density, fast kinetics, and structural durability for advanced lithium-ion battery anodes.

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