Li4Ti5O12 Coatings for Improved Stability As Lithium-Ion Battery Anodes

The current energy economy poses many risks that will need to be addressed, including 1) continued depletion of limited fossil fuel resources, 2) accelerating demand for oil, especially in developing nations, and 3) rising global temperatures attributed to carbon dioxide emission by fossil fuels.  The bulk of wasteful energy use and carbon dioxide emissions stems from the inefficient combustion reactions used to power automobiles.  Lithium-ion energy storage devices are perfectly poised to tackle the developing energy crisis because they are relatively nonpolluting, have readily available precursor materials, and alleviate the need for fossil fuel sources by providing an excellent fuel economy when coupled with internal combustion engines in hybrid electric vehicles.  Li₄Ti₅O₁₂ (LTO) is a promising candidate in the next generation of lithium-ion materials that is extremely inexpensive to produce, environmentally friendly, and has demonstrated excellent characteristics for use in high-rate applications (e.g., hybrid vehicles).  However, under extreme but operationally relevant temperature conditions, LTO has been shown to emit hydrogen and other flammable gases that prohibit its use in many applications.  New materials must be synthesized that mitigate the generation of flammable gases while maintaining the desirable performance properties of LTO.   

The purpose of this project is to successfully synthesize materials that incorporate ZrO₂ coatings onto the surfaces of the LTO particles to reduce the reactivity of the LTO with the electrolyte while retaining desirable electrochemical properties.  Zirconia coatings were chosen because they have been shown to reduce the reactivity of other lithium-ion materials and are considered to be very stable in a variety of other applications. 

Size-tunable, microsphere TiO₂ particles are synthesized via sol-gel method and used to prepare LTO through solid-state and hydrothermal reactions.  Zirconia coatings are then deposited on the surface of the LTO particles.  Electrochemical and materials characterization was performed for the spherical TiO₂, coated and uncoated LTO particles.  Preliminary results demonstrate alterations in the surface of coated LTO particles that retain their desirable electrochemical performance properties.  Further work is needed to improve the uniform distribution of the zirconia coating and enhance the sphericity of prepared LTO particles.