High-performance aqueous sodium-ion storage using scalable and surfactant-free flower-like manganese oxide/reduced graphene oxide electrodes

In this study, we present a straightforward, precipitant-free, aqua-assisted solvothermal approach for synthesizing Mn₃O₄ flower-like architectures. With the addition of a minimal amount of water, the solvothermal process has greatly impacts the morphology and porosity of the flower-like Mn₃O₄. The addition of a small amount of water during the solvothermal process significantly influences the morphology and porosity of the Mn₃O₄, as evidenced by the scanning electron microscopy analysis and surface area analysis. The reaction mechanism leading to the formation of Mn₃O₄ is thoroughly discussed, highlighting the critical role of water in promoting the development of flower-like structures. The resulting Mn₃O₄ particles exhibit a favorable surface area, contributing to their enhanced Na⁺-ion transport and storage. The electrochemical performance of the synthesized structures demonstrates high specific capacitance 177.8 F/g at 0.5 A/g, excellent capacity retention over extended cycling, and stability. Additionally, Mn₃O₄ nanoflowers were assembled in asymmetric aqueous sodium-ion capacitor configuration with reduced graphene oxide@carbon cloth negative electrode. The sodium-ion capacitor achieves a high energy and power density of 36 Wh/g and 2750 W/kg, respectively, along with superior cycling stability, thus rendering the composite structures promising.