High-performance supercapattery with nanotube-TiO2/carbon nano tubes anode and coconut-shell-derived activated carbon cathode

Abstract

This paper aims to present the fabrication of a Li-ion supercapattery by an anode designed for a lithium-ion battery (nanotube TiO2 (NT-TiO2) and carbon nanotubes (CNTs), namely as NT-TiO2/CNTs) with a cathode designed for an electrochemical double-layer capacitor (derived activated carbon), resulting in high energy and densities of power. The hydro¬thermal route formed the composite NT-TiO2/CNTs. DFT calculations provide the Li absor¬bed inside and outside isolated CNTs and NT-TiO2/CNTs. The lithium diffusion energy barrier results show that Li is preferred energetically inside CNT. The energy barrier of Li diffusion for isolated CNTs is 1.21 eV, whereas that of NT-TiO2/CNTs is computed at 0.69 eV. It demonstrated that the functionalized NT-TiO2 improves the performance and the rate of Li diffusion of the isolated CNTs system, which agrees with the experiment. The results illustrate that the synergistic effect of high conductive CNT networks and well-dispersed NT-TiO2 structure can enhance hybrid capacitors' power and energy density through the brief diffusion routes for Li-ions and rapid transference of electrons. A Li-ion supercapattery battery, NT-TiO2/CNTs-1||activated carbon (AC), achieved an energy density of 48.9 Wh kg-1, surpassing supercapacitors, and a power density of 1667 W kg-1 at a current rate of 1 A g-1, exceeding that of Li-ion batteries.

Keywords

• TiO2/carbon nanotubes composite
• hybrid Li-ion capacitor
• density functional theory calculations
• energy density
• power density