Abstract
Lithium titanate has been successfully used as anode for lithium ion batteries due to its high rate capability, enhanced structural stability and safety, making it suitable for application in electric vehicles (EV) and hybrid electric vehicles (HEV). Current synthesis methods involve multiple steps including the production a nanoparticle powder, followed by coating the powder onto a conductive substrate along with conductive additives and binding agents and finally annealing. These processes do not offer sufficient control over the morphology, crystallinity and orientation of the active material. A single step process for the synthesis of nanostructured thin films directly on the current collector would facilitate the fabrication of nanostructured anodes without the use of any binding agent.
The aerosol chemical vapor deposition (ACVD) process is a single step, low cost method for the synthesis of nanostructured thin films. ACVD has been successfully demonstrated for the synthesis of metal oxides such as TiO
2
and NiO and for mixed oxides of Al
2
TiO
5
. The process involves decomposition of a metal organic precursor in the reactor to yield metal oxide molecules which grow by homogenous nucleation to yield particles. These particles deposit onto a heated substrate where they sinter to form thin films of different morphologies. The synthesis of mixed oxide thin films involves heterogeneous nucleation of multi-component metal oxides to yield mixed oxide particles. The process allows for the synthesis of different nanostructures with varying morphologies, which include dense, single crystal columnar, granular and branched morphologies, through control over various process parameters.
This work focuses on controlling the composition and morphology of lithium titanate thin films synthesized by the ACVD process. Control over the characteristic times and the reaction rates was used to control the morphology and the stoichiometry of the synthesized thin films. The surface morphology of the films was characterized by scanning electron microscopy and the crystal structure was examined by x-ray diffraction analysis. X-ray photoelectron spectroscopy was used to probe the chemical composition of the films. Electrochemical characterization of the synthesized nanostructured anodes was performed in half cell configurations vs Li/Li
+
. The effect of stoichiometry and composition of the film on the electrochemical performance will be presented.