Construction of spherical NiO@MnO2 with core-shell structure obtained by depositing MnO2 nanoparticles on NiO nanosheets for high-performance supercapacitor

Abstract

The 3D spherical NiO@MnO2 composites grown on Ni foam with core-shell structure were prepared by a hydrothermal process followed by a chemical bath deposition process, and then the mechanism improving the electrochemical performance of NiO by MnO2 modification were investigated by the first-principles calculations for the first time. This core-shell structure promotes an efficient contact between electrolyte and active materials, and the distinct architecture can offer fast transfer channels of ion and electrons. The initial capacitances of NiO, NiO@MnO2 (deposition time of MnO2 is 20 min), NiO@MnO2 (deposition time of MnO2 is 30 min) and NiO@MnO2 (deposition time of MnO2 is 60 min) at 10 A g−1 are 931.6, 1064.4, 1227.2 and 766.8 F g−1, respectively. After 10000 cycles, the reversible capacitances attenuate to 352.8, 661.0, 1089.4 and 616.6 F g−1, respectively. NiO@MnO2 (deposition time of MnO2 is 30 min) shows the most excellent reversible capacitance at each cycle and the highest retention rates after 10000 cycles among all samples. The first-principles calculation confirms that a strong interfacial interaction between NiO and MnO2 can be generated, and then the atomic relaxations at the interface are rather small due to the well-matched interface and epitaxial bonding, resulting in a relatively small interfacial polarization of NiO@MnO2 composites during cycling. The outstanding rate capability and cycle performance of NiO@MnO2 (deposition time of MnO2 is 30 min) electrode are attributed to the synergistic effect and particular 3 D architectures.