Large Li-Ion Insertion Capacity of Thin-Wall Anatase TiO2 Nanotubes at 25 °C-55 °C

Abstract

Anatase TiO<inf>2</inf> was prepared in the form of nanotube arrays by anodic oxidation of Ti foil followed by annealing at 400 °C. Electrochemical experiments, which included cyclic voltammetry (CV), galvanostatic (GS) cycling and electrochemical impedance spectroscopy (EIS) were conducted in 1 M solution of LiClO<inf>4</inf> in propylene carbonate (PC) at temperatures 25 °C-55 °C. CV experiments, at scan rates 5-50 mV·s⁻¹, demonstrated with increasing temperature a large increase in the intensity of the redox peaks along with a decrease in the peak-to-peak separation. GS cycling showed large increase of capacity of thin-wall TiO<inf>2</inf> nanotubes with increasing temperature, which attains 357 mAh·g⁻¹ at 55 °C during lithiation at current rate 5.3 C, with capacity retention of 98.5% and Coulombic efficiency of 97.5%. Surface storage and development of secondary voltage plateau strongly contribute to such a large capacity value. EIS showed a multiple decrease in solid electrolyte interphase (SEI) layer resistance and charge transfer resistance with temperature rising up to 55 °C.