Fabrication of hollow lithium titanate material by electrospinning

Lithium titanate (Li₄Ti₅O₁₂, LTO) is an important material to be used as an anode for LIBs (Li⁺ ion battery). LTO is a zero-strain material (i.e., no structural change occurs during Li insertion/extraction). Although LTO is a very safe material that can be used as an anode material in high and low temperature environment, its rate capability is compromised by its low electronic conductivity and poor Li⁺ diffusion coefficient. In the recent years, considerable research around the world has focused on improving LTO rate performance. Efforts to achieve better electrical conduction between LTO particles have included LTO particle size control, conductive-material surface coatings, and alien ion doping. However, in this study electrochemical properties were improved by changing the morphology of LTO. Based on traditional electrospinning technology, LTO fibers with a hollow structure were produced using a nested coaxial nozzle modified from the conventional spinning nozzle and coaxial cospinning with two different solutions. A comparison of this results with those of solid LTO prepared by traditional electrospinning technology demonstrates that hollow LTO is characterized by uniform particle size and no agglomeration, along with an obvious hollow structure, clear crystal lattice stripes, and good crystallization property. The specific surface of this hollow LTO is 1.3 times than its solid counterpart. This morphological change greatly improves the electrochemical performance of the material. Although the discharge specific capacities of both the solid and hollow LTO are close to the theoretical value for small ratios, the hollow LTO is superior to its solid counterpart at 20C. The discharge specific capacity of the hollow LTO can reach 130 mA·h·g^-1 at 20C, and after 200 cycles, its capacity retention ratio remains at 98%, which suggests good stability. Cyclic voltammetry and AC impedance curves also show that the hollow structure reduces the degree of polarization and the electrochemical reaction impedance of LTO, which makes LTO more conducive to electrochemical reaction.