A three-dimensional NiCo-LDH array modified halloysite nanotube composite for high-performance battery-type supercapacitor

Highlights: • A novel 3D nanocomposite with a core-shell structure was designed. • The nanocomposite contains two natural abundant clay materials. • HNTs as the core was treated by a dual surface modification including a carbonization process and cobalt doping. • NiCo-LDH/D-HNTs has a specific capacity of 1401.4 C g^-1 at 1 A g^-1. -- Abstract: Battery-type supercapacitors have aroused great interest in the field of energy storage devices and nickel cobalt layered double hydroxides (NiCo-LDHs) show great potential as electrode materials. However, the intrinsic low conductivity and possible agglomeration limit a wider application. In this work, a novel three-dimensional composite material (NiCo-LDH/D-HNTs) with a core-shell structure was prepared by self-assembling NiCo-LDHs nanosheets on dual surface-modified halloysite nanotubes (D-HNTs) via in-situ electrodeposition and hydrothermal method. HNTs were pretreated by a dual surface modification for the first time including a carbonization process and cobalt doping to enhance electrical conductivity and chemical stability. This multicomponent hierarchical nanocomposite, NiCo-LDH/D-HNTs, has a specific capacity of 1401.4 C g^-1 at 1 A g^-1, a rate capability of 52.9% increasing the current density to 30 A g^-1, and cycling stability of 80.8% after 2000 cycles. With the tubular support, the electrochemical properties of NiCo-LDHs were extended in addition with the pseudocapacitance of HNTs. Besides the excellent electrochemical performance, NiCo-LDH/D-HNTs nanocomposites possess many advantages of abundance in nature, hydrophilicity, low cost and scalability. NiCo-LDH/D-HNTs nanocomposite can be considered as a promising, environmentally friendly, and cost-effective electrode material for supercapacitors and other energy storage devices.