Abstract:

Transition metal oxides (TMOs) with high theoretical specific capacitance have attracted considerable attention in the field of supercapacitors; however, their high-rate and long-term applications are still challenging. In this work, a series of ternary NiCuMn-based electrodes (MPO-NiCuMn) with high-electrical conductivity and porous structure was prepared by combining dealloying and self-combustion methods and using the sandwich-like NiCuMn/Ni/NiCuMn as the mother alloy. Then, the effect of Cu doping on the electrochemical properties was investigated. The results show that the Ni-supported nanoporous alloy layers were formed by the one-step dealloying process. Because of the high-specific surface energy of the NP-NiCuMn precursor, the alloy can self-combust in an open system by partial self-sacrifice. By this one-step combustion method, the final electrodes could simultaneously enhance the electrical conductivity and promote the mass loading of TMOs. The electrochemical performance shows that the MPO-Ni₁₅Cu₁₅Mn₇₀ electrode with 15% Cu dopant has a maximum areal capacitance of 12.2 F/cm² at a high current density of 50 mA/cm², much higher than that of MPO-Ni₂₀Cu₁₀Mn₇₀ (5.6 F/cm²) and MPO-Ni₁₀Cu₂₀Mn₇₀ (7.7 F/cm²) electrodes. The assembled symmetric supercapacitor demonstrates outstanding cyclic stability with a capacitance retention of 95.7% after 8000 cycles at a current density of 50 mA/cm², as well as a high-rate performance. It also shows a high energy density of 241 mWh/cm² at a power density of 4.2 mW/cm². This study verified that doping using appropriate amounts of Cu can play a major synergistic role in effectively improving the energy storage performance of supercapacitors.

Key words: dealloying, spontaneous combustion oxidation, transition metal oxide, electrochemical performance