Highly loaded manganese oxide with high rate capability for capacitive applications

Manganese oxide (MnOx), as a benchmark pseudocapacitive material, has aroused great interest in electrochemical energy storage community. However, ion transport is seriously hindered in the densely packed bulk materials of highly loaded MnOx electrodes. Here, the structural engineering for the electrodeposited MnOx materials is realized by tuning the concentration of the complexing agents used in the electrodeposition process. The fabricated highly porous nanostructure in the thick oxide layer can minimize the ion diffusion distances to the interior electrode surface, and the optimized content of the hydrous species can facilitate the solid-phase diffusion of the electrolyte ions in the oxide lattice. The deposited MnOx electrode with a high mass loading of 7.02 mg cm−2 exhibits excellent rate capability due to the dual-tuning effect. An excellent specific capacitance of 161.2 F g−1 (1.13 F cm−2) at a high current density of 20 mA cm−2 can be obtained, which is comparable to the capacitance delivered by the low mass loading electrode at the same current density (214.8 F g−1 for 0.54 mg cm−2 sample), indicating its high material utilization. The performance of the fabricated electrode ranks on the top of the reported MnOx materials with high mass for capacitive applications.