Hierarchical graphene oxide/manganese dioxide/cobalt-nickel layered double hydroxide electrodes for high energy density asymmetric flexible supercapacitor

Currently, the limited energy density constrains potential applications of flexible supercapacitors. Expanding the voltage window is an effective solution, which is strongly dependent on the design of the electrode material. Herein, hierarchical graphene oxide (GO)/manganese dioxide (MnO2)/cobalt-nickel layered double hydroxide (CoNi-LDH) onto activated carbon cloth (CC/GMCN) electrodes are fabricated through a sequential deposition approach. Density functional theory (DFT) calculations demonstrate that GO, MnO2 and CoNi-LDH can be tightly bound together by electrostatic interactions, declaring the construction of this triple heterogeneous structure is efficient and feasible. The assembled asymmetric supercapacitor, using the CC/GMCN as positive electrode and activated carbon (AC) as negative electrode, exhibits a voltage window of 1.9 V, a specific capacitance of 163.95 F/g at 1 A/g, along with an energy density of 82.12 W h kg−1 at a power density of 949.97 W kg−1. Furthermore, the device displays exceptional bending resistance, with the specific capacitance retaining 94.73 % after undergoing 1000 bending cycles. After 10,000 charging and discharging cycles, the device maintains a capacity retention of 92.62 % and sustains an almost 100 % coulombic efficiency. The prepared device underscores the promising real-world applications, and this research introduces an effective avenue for advancing the field of next-generation flexible supercapacitors.