Facile preparation of Ni-doped MnCO₃ materials with controlled morphology for high-performance supercapacitor electrodes

Doping homogeneous elements and conducting morphological adjustment as commonly-used modification methods are both effective to promote the electrochemical properties of electrode materials. In this work, nickel-doped manganese carbonate with 3D flower-like structure was synthesized by a one-step hydrothermal method, and the corresponding growth mechanism was investigated. The electrochemical characteristics of as-fabricated electrode materials were measured, among which 3D self-assembled Ni_0.2Mn_0.8CO₃ nanoflower with large surface area exhibited superior areal capacitance of 583.5 F g⁻¹ at 1 A g⁻¹ (fourfold more than MnCO₃ microcubes), excellent electrical conductivity as well as satisfactory cycling stability (84.78% capacitance retention after 2000 cycles at 2 A g⁻¹). In addition, the asymmetric supercapacitor assembled with Ni_0.2Mn_0.8CO₃ as cathode and commercial activated carbon as anode displayed a high energy density of 24.1 Wh kg⁻¹ at the power density of 0.74 kW kg⁻¹ and showed a desirable cycle life. In summary, the unique 3D flower-like Ni_0.2Mn_0.8CO₃ nanomaterial could be regarded as a promising electrode material for high-performance supercapacitors.