Design and fabrication of hydrotalcite-like ternary NiMgAl layered double hydroxide nanosheets as battery-type electrodes for high-performance supercapacitors.

Hydrotalcite is an abundant mineral in nature and can be cost-effectively prepared in the laboratory, but there is almost no discussion about its application in the field of supercapacitors. Herein, hydrotalcite-like ternary NiMgAl LDHs with unique ultrathin nanosheets were designed and fabricated by a facile hydrothermal method. The preparation conditions, such as Ni/Mg molar ratio and hydrothermal reaction time, are evaluated carefully. The physical and chemical properties were also evaluated by various characterization techniques such as XRD, FIB/SEM, EDS, TEM, XPS and BET. The electrochemical behaviors of present samples were determined by CV, CC and cycling tests in a three-electrode system. As a battery-type electrode material in a supercapacitor, owing to the advantage of its unique layered structure, high specific area and obvious redox states, the fabricated NiMgAl LDH-24 h nanosheets present an outstanding specific capacitance of 219.2 mA h g at a current density of 1 A g and superior cycling stability with 86.1% capacitance retention over 5000 cycles. Although 45.7% capacitance retention is not satisfactory when the current density increases from 1 to 3 A g due to the NiMgAl LDH's low effective mass and conductivity, it is still a successful case for hydrotalcite application in supercapacitors by doping with Ni to achieve high electrochemical performance. The design and fabrication strategy can facilitate the application of the natural hydrotalcite mineral in the energy storage field.