Thermally engineered cationic defects in MOF-derived inverse spinel Al8[Fe16-xMnx]O32 for high-energy hybrid supercapacitors

초록

A novel thermal strategy precisely tailors Mn-based cationic defects in MOF-derived inverse spinel Al8Fe16O32 embedded within partially graphitized carbon. This defect engineering greatly enhances electrical conductivity, ion transport, redox activity, and structural stability. As supported through XRD, HR-TEM/STEM mapping, XPS, and XAS (XANES/EXAFS), elevated temperatures and extended soak times promote cation mobility, antisite exchange, vacancy equilibration, and phase transitions. Further, due to enriched Fe/Mn defect sites and enhanced redox/pseudo capacitance behaviour, the defective MnOx-(Al-8)[Fe16-xMnx]O-32@AHGC electrode demonstrates a much higher specific capacitance (96 F g(-1)) than pristine Al8Fe16O32@AHGC (12.7 F g(-1)). The assembled HSC device AC // MnOx-(Al-8)[Fe16-xMnx]O-32@AHGC delivers 78 % rate capability, an energy density of 25.4 Wh kg(-1) (similar to 40 % higher than that of pristine), and 89 % capacitance retention after 10,000 GCD cycles at 7.5 A g(-1). This work highlights the potential of defect engineering in inverse spinel oxides combined with MOF-derived hierarchical partially graphitized carbon for advancing next-generation energy storage systems.

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