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

Abstract

Anatase TiO2 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 1M solution of LiClO4 in propylene carbonate at temperatures 25-55°C. CV experiments, at scan rates 5-50 mV•s1, 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 TiO2 nanotubes with increasing temperature, which attains 357 mAh•g1 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 layer resistance and charge transfer resistance with temperature rising up to 55°C.