Self-supported ultrathin NiCo-LDH nanosheet array/Ag nanowire binder-free composite electrode for high-performance supercapacitor

The supercapacitor (SC) based on nickel cobalt layered double hydroxide (NiCo-LDH) has aroused great interest in the field of energy storage. However, the agglomeration and low electrical conductivity are unfavorable for electrochemical performance. Herein, Ag nanowires (Ag NWs) was first dip-coated on nickel foam (NF) to form a conductive substrate, on which the NiCo-LDH nanosheet array in-situ grew to construct an efficient three-dimensional (3D) self-supported hierarchical structure NiCo-LDH/Ag NWs/NF electrode. The presence of Ag NWs inhibits aggregation of LDH nanosheets and accelerates the electron transfer. Electrochemical studies exhibit that NiCo-LDH/Ag/NF hybrid electrode possesses the higher specific capacitance of 2920.6 F g⁻¹ at a current density of 5 A g⁻¹ and excellent cycling stability (89.8% after 2000 cycles) compared with the electrode without Ag NWs. The asymmetric supercapacitor (ASC) with the NiCo-LDH/Ag/NF heterostructure as the positive electrode and active carbon (AC) as the negative electrode displays a high energy density of 42.9 Wh kg⁻¹ at a power density of 800 W kg⁻¹. When two aqueous ASCs were assembled in series and charged for only 1 min, the stored energy was capable of powering two green light-emitting-diodes (LEDs) for more than 3 min, indicating NiCo-LDH/Ag/NF electrode material shows great potential application in supercapacitor.