Three-dimensional nanobranched TiO₂-carbon nanotube for high performance supercapacitors

Developing high capacity solid-state super capacitors and exploring their storage mechanism is one of the ongoing scientific topics. Here a novel TiO₂-carbon nanotube (CNT) electrode is prepared by electrochemical deposition of TiO₂ nanostructures on the CNT film. In situ Raman spectroscopy showed that the ion transfer kinetics of 3D rutile-based TiO₂ were mainly controlled by ion adsorption. Symmetric solid-state supercapacitors compose of two TiO₂-CNT electrodes and H₂SO₄-polyvinyl alcohol gel electrolyte. The devices show a high energy density of 82.5 Wh kg⁻¹ and specific capacitance of 345.7F g⁻¹ at 1.0 A g⁻¹. Furthermore, the TiO₂-CNT supercapacitor illustrates excellent cyclic stability with capacitor retention of 93.3% after 10,000 cycles, and a low leakage current of 9 μA after 2 h. This may due to the matching of the diffusion path topology of the rutile-doped less anatase structure. These results demonstrate that the TiO₂-CNT supercapacitor may bring new opportunities to the power supply of portable electronics in the future.