Metal-organic framework derived functional MnO2 via an in-situ oxidation strategy for advanced quasi-solid-state supercapacitors

Accurately controlling the morphology and structure of metal oxides faces huge challenges, which also limits their applications in different fields. Here, we report an in-situ oxidization strategy to design hollow spherical MnO2 (HS-MnO2) at room temperature based on the Mn-based metal-organic framework precursor. During the in-situ oxidization process, the obtained HS-MnO2 remains a hollow spherical structure with abundant pre-inserted Na+ and oxygen vacancies, which contributes to addressing its issues of volume expansion, low ionic diffusion rate, and low electronic conductivity. Consequently, the HS-MnO2 electrode exhibits high reversible capacitance (304.3 F g(-1), 0.5 A g(-1)), high cycle stability (77.6% capacity retention for over 20,000 cycles at 10 A g(-1)), and excellent rate performance in supercapacitor applications. Importantly, the MnO2-based quasi-solidstate supercapacitor can power different devices, which shows its good application prospect. Our work provides new insights into the preparation of transition metal oxides with controllable structures via a mass-productive strategy with low cost to fulfill their potential in energy storage devices.