The growth of nickel-manganese and cobalt-manganese layered double hydroxides on reduced graphene oxide for supercapacitor

Pure Ni-Mn layered double hydroxide (LDH), Co-Mn LDH with a flower-like morphology and sandwich-like Ni-Mn LDH/reduced graphene oxide (rGO), Co-Mn LDH/rGO hybrids are fabricated via a simple co-precipitation method. In the hybrids, Ni-Mn and Co-Mn hydroxide nanoflakes are tightly anchored on the both surfaces of rGO, leading to the composites with high specific surface areas. Electrochemical measurements prove that rGO can improve the capacitance and cyclic stability of the hybrid materials and that Ni-Mn LDH delivers a much higher specific capacitance but a worse cycling performance than Co-Mn LDH. A high specific capacitance of 1635 F g−1 at 1 A g−1 and a high rate retention of 71% at 10 A g−1 are achieved for Ni-Mn LDH/rGO. A hybrid capacitor with Ni-Mn LDH/rGO as positive electrode and activated carbon as negative electrode is assembled. It possesses a specific capacitance of 84.26 F g−1 at 1 A g−1 and an energy density of 33.8 Wh kg−1 within a potential window of 1.7 V.