High Surface Area Lithium Titanate Electrode for Li-ion Batteries

Abstract

A lithium titanate (Li4Ti5O12) anode composed of submicron fibers with nanosize grains was fabricated by electrospinning from spin dopes prepared from nanoparticles of lithium titanium oxide (Li4Ti5O12) and polyvinylpyrolidone (PVP) in a solvent. Optimal electrospinning conditions and solvent composition that could be electrospun into fibers under a variety of ambient conditions were determined. Pyrolyzing the electrospun fibers at high temperatures (700°C for 5 hours in air) and plasma-treating in oxygen (500 m Torr for 30 m) revealed a nano-size grain structure within the individual fibers. Electrochemical testing with metallic lithium as a reference electrode displayed promising capacities for three charging cycles. The C rates displayed complete charging when the charging time was at least 10 minutes. However, faster charging resulted in a loss of capacity to as low as 50% when charged in less than three minutes. This degradation appears to be triggered by trace amounts of a secondary phase introduced by standard purity precursors used for preparing lithium titanate. Evidence for this was found using x-ray fluorescence revealing the presence of iron and silicon oxides.