265 1. INTRODUCTION During the past two decades, the requirements for energy stor- age in both portable and static applications have increased tremen- dously. As the storage and power demands placed on batteries have increased, the associated materials systems have evolved. However, cost reduction and performance improvements are still necessary to address future energy storage requirements. These limitations can be overcome only by major advances in new mate- rials needed for sustainability; providing energy independence for both present and future generations. Lithium ion cells continue to be a promising source of energy for portable applications in the future [1–4]. Many of these new applications of lithium ion batter- ies require high energy and power densities, quick recharging times, and safe operation at variable ambient temperatures. Typi- cally, intercalated lithium compounds such as LiCoO 2 , LiMn 2 O 4 , LiFePO 4 , LiC 6 and Li 4 Ti 5 O 12 are the preferred electrodes in such cells [4–9]. The preparation and electrochemical performance of lithium titanate (Li 4 Ti 5 O 12 ) is of special interest due to the poten- tially greater safety associated with its use as an anode material. Nanostructured electrodes offer a tremendous potential for de- veloping high power density lithium ion batteries with high rate capabilities. The advantages of nanostructured electrodes are (i) A large amount of Li + is found at surfaces because the surface area/weight ratio is very large for nanoparticles. Thus, diffusion reactions occur mostly near the particle surface without relying on slow solid-state diffusion of Li + within the bulk. This facilitates rapid charge-discharge. (ii) Since the important electrochemical reactions occur mostly in the surface regions of particles, stress- induced lattice deformation from repeated charge/discharge is minimized. This improves cycle life and coulomb efficiency. (iii) The path length for solid-state diffusion is small as the particle diameter (d) is greatly decreased. This dramatically reduces inter- calation/de-intercalation time (t ~ [d 2 /D] where t = intercala- tion/deintercalation time, d = particle/grain diameter, and D = the diffusion coefficient). (iv) Nanoparticles provide a large interface area for Li + insertion/extraction and hence increase the specific capacity. (v) At high C-rates, current density increases and slow Li + transport causes concentration polarization within the active material, preventing full utilization of the capacity. This problem is minimized for nanoparticles since active surface area increases *To whom correspondence should be addressed: Email: lannuttj@matsceng.ohio-state.edu Phone: (O): 614-292-3926, Fax. (O): 614-292-1537 High Surface Area Lithium Titanate Electrode for Li-ion Batteries Nishant M. Tikekar 1 , John J. Lannutti 1,* , Ramchandra Rao Revur 2 and Suvankar Sengupta 2 1 Department of Materials Science and Engineering, 448 MacQuigg Labs, 105 W Woodruff Avenue, Ohio State University, Columbus OH 43210, USA 2 Metamateria Technologies, 1275 Kinnear Road, Columbus OH 43212, USA Received: November 30, 2011, Accepted: January 09, 2012, Available online: April 11, 2012 Abstract: A lithium titanate (Li 4 Ti 5 O 12 ) anode composed of submicron fibers with nanosize grains was fabricated by electrospinning from spin dopes prepared from nanoparticles of lithium titanium oxide (Li 4 Ti 5 O 12 ) 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 deter- mined. Pyrolyzing the electrospun fibers at high temperatures (700˚C for 5 hours in air) and plasma-treating in oxygen (500 mTorr 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 degrada- tion 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. Keywords: Lithium titanate, Li-ion battery, Electrospinning, Surface area Journal of New Materials for Electrochemical Systems 15, 265-270 (2012) © J. New Mat. Electrochem. Systems