Dual-channels engineering of carbon tube/NiCo-LDH composites for enhanced ion diffusion and electron transfer

Abstract

Dual-Phase engineering for enhanced ion diffusion and electron transfer by structural design and electronic modulation is an effective strategy to construct high-performance electrode materials. In this paper, biomass-based carbon tube/Ni-Co bimetallic hydroxide (CT/NiCo-LDH) composite was synthesized using biomass carbon tube as substrate, and NiCo-LDH composed of thin nanosheets is grown on the surface of the carbon tube. The carbon tube not only has a large specific surface area, but is rich in oxygen-containing functional groups, which is conducive to NiCo-LDH loading and nucleation. The nanoflower-like hierarchical structure enlarged ions intercalating channels, which is conducive to energy storage. The Ni-doping and combination of high specific capacity of NiCo-LDH and high electrical conductivity of carbon materials cooperatively improved the electrochemical kinetics and cycling stability as fast ion/electron dual pathways. The electrochemical performances are further suggested by density functional theory calculations and capacitance contribution fitting, which provides theoretical assistance for the excellent reaction kinetics. The specific capacity of the composite electrode was 1927 F g⁻¹ at 0.5 A g⁻¹, and possessed excellent capacitance retention rate of 82 % at 20 A g⁻¹. The asymmetric supercapacitor fabricated using CT/NiCo-LDH positive electrode and biomass carbon negative electrode displayed a high energy density of 90.4 W h kg⁻¹. The current research provides a new idea for the design of fast ion/electron dual pathways electrodes and high energy density supercapacitors.