Electrochemical behavior of anodically obtained titania nanotubes in organic carbonate and ionic liquid based Li ion containing electrolytes

Abstract

Amorphous and anatase TiO2 nanotube layers were synthesized by means of Ti foil anodic oxidation performed in ethylene glycol based electrolyte containing fluoride ions. A typical surface structure of TiO2 nanotubular layer, well aligned nanotubes with inner diameter of 70–100nm and wall thickness of about 10–15nm was obtained. Both amorphous and converted to anatase nanotube layers were mechanically stable and well adherent to the Ti current collector.The nanostructured Ti/TiO2 layers were tested as a current collector – anode material system for Li-ion intercallation in 1M LiPF6 ethylene carbonate/dimethyl carbonate (EC:DMC) and in 1-buthyl-1-methyl pyrrolidinium is (trifluoromethyl) sulfonylimide ([BMP][TFSI]) containing 1M Li[TFSI]. The potential window of [BMP][TFSI] measured on Ti current collector remains not considerably influenced by addition of Li[TFSI]. The type of electrolyte does not influence the voltammetric behavior of the amorphous TiO2 nanotube layers, whereas in case of anatase there is a definite inhibition of the Li intercalation in 1M Li[TFSI] [BMP][TFSI], expressed by increasing the peak-to-peak voltage difference between the Li insertion and de-insertion processes. The observed phenomenon is discussed in terms of viscosity difference between both electrolytes.TiO2 nanotube structures displayed a stable galvanostatic cycling, reaching the theoretical capacity of TiO2 structure and high current efficiencies in both Li ion containing media.