TiO2 Nanocomposites for Energy Storage Applications

Abstract

This research studied tube super dielectric material (TSDM) based novel paradigm supercapacitors (NPS). TSDM are dielectric materials with remarkably high dielectric constants (>105) comprising of porous electrically insulating solids in which the pores are filled with ionic species. This research aimed to fabricate TSDM-based NPS and investigate the impact of the pore size (nanotube diameter) and the type of ionic species on the capacitance, dielectric constants, and energy densities of the assembled NPS. In this work, the TSDM were synthesized using TiO2 nanotube arrays (NTAs) filled with either an aqueous salt solution (9M NaNO3) or an ionic liquid ([EMIM][BF4]). A multi-step anodization process was used to synthesize TiO2 NTAs with various nanotube diameters. The capacitance and dielectric constant of the synthesized NPS were found to increase with increasing nanotube diameter, regardless of the type of ionic species. Additionally, the ionic liquid-based TSDM exhibited a broader operating potential (0 V to 4 V), a significant improvement over other aqueous salt solution-based TSDM reported previously. Since energy density is proportional to the square of the operating potential, ionic liquid-based TSDM had higher energy densities than their aqueous salt solution counterparts. The TSDM-based NPS with the ionic liquid and large diameter size displayed a significantly high energy density of 415 J/cm3.