A Novel Oxidation–Reduction Route for the Morphology-Controlled Synthesis of Manganese Oxide Nanocoating as Highly Effective Material for Pseudocapacitors

In recent years, pseudocapacitors have been receiving much attention as low-cost and safe energy storage technology for emerging applications in flexible and safe devices. However, creating high-energy-density electrode materials is now the main limit for high-performance pseudocapacitors. In this work, we propose a novel reduction route for the synthesis of uniform MnO2 nanocoating with porous morphology on nickel foam via the SILD method as electrode material for high-effective pseudocapacitors. The obtained nanocoatings were characterized by SEM, TEM, EDX, XRD, XPS, and electrochemical techniques. Comparisons of MnO2 coatings were conducted to obtain the reduction and oxidative routes of synthesis. The influence of the oxidation–reduction reaction type on the structures, morphologies, and capacity performance of manganese oxide was investigated. The results show that the nanocoatings synthesized via the reduction route were formed of amorphous uniform ultra-thick coating MnO2 with a porous morphology of “nanoflakes.” Due to the unique morphology and uniform coating of nanosized manganese oxide, electrodes based on this process have shown a high specific capacity (1490 F/g at 1 A/g) and excellent cycling stability (97% capacity retention after 1000 charge–discharge cycles).