Facile synthesis of foamed-nickel supporting MnO ₂ as binder-less electrodes for high electrochemical performance supercapacitors

The current challenge of the still poor electronic conductivity is one of the major bottlenecks to obtain the large reversible capacitance and rapid rate capability for MnO ₂ -based supercapacitor electrodes. Herein, we report the synthesis of a binder-less Ni/MnO ₂ electrode with hierarchical MnO ₂ nanosheets anchoring on the foamed-Ni support frameworks, and the mass loadings of MnO ₂ on the foamed-Ni and the nanostructural morphology are optimized to enhance its electrochemical performance. Such hierarchical nanosheet structure of MnO ₂ can improve its electrolyte-accessible surface area and the foamed-Ni framework can effectively enhance its electronic conductivity, which can be beneficial to improve its capacitance and rate capability. The Ni/MnO ₂ electrodes reveal an areal capacitance of 2.31 F cm ⁻² at the current density of 1 mA cm ⁻² , which can maintain 1.48 F cm ⁻² (64.1%) at 20 mA cm ⁻² , exhibiting high capacitance and excellent rate capability. Moreover, the Ni/MnO ₂ electrode-based supercapacitor exhibits a superior energy density of 160.1 mWh cm ⁻² and an outstanding cycling stability of 86.8% capacitance retention after 9000 cycles, indicating that such binder-less Ni/MnO ₂ offers a promising electrode material for the high-performance supercapacitor. [Figure not available: see fulltext.].