Effect of 0.5 M NaNO3: 0.5 M KNO3 and 0.88 M LiNO3:0.12 M LiCl Molten Salts, and Heat Treatment on Electrochemical Properties of TiO2

Abstract

The compounds, TiO2−1 & −2 were synthesized by 0.5 M NaNO3: 0.5 M KNO3 (I) and 0.88 M LiNO3:0.12 MLiCl (II) salts at 510°C and 280°C, resp.., XRD studies show single anatase phase with characteristic tetragonal lattice parameter values of a ∼3.78 Å and c ∼ 9.51 Å. The TEM images show aggregates of 10–30 nm sized nanosquares (TiO2−1) and spherical particles (TiO2−2). Surface area of the TiO2 powders were 74 and 200 m2 g−1, resp. for 1 and 2. Upon heat-treatment (TiO2−2) from 500°C to 850°C, the surface area decreases from 80 to 0.7 m2 g−1. Cyclic voltammetry studies show cathodic and anodic peaks at ∼1.7 and ∼ 2.0 V, resp. for both bare and heat treated TiO2 up to 750°C. Galvanostatic cycling studies show that the first discharge-charge capacity values are 244 and 198 (±3) mAh g−1 resp. for TiO2−1 at a current of 33 mA g−1 in the voltage window, 1.0–2.8 V vs. Li/Li+. TiO2−2 nanoparticles show a less capacity fade during cycling and delivered first discharge-charge capacity values of 340 and 253 (±3) mAh g−1, resp. at a current rate of 33 mA g−1. The effects of heat-treatment and Li-cycling at a cutoff voltage (0.005 V) were studied and discussed reaction mechanism.