Investigation into the Surface Chemistry of Li4Ti5O12 Nanoparticles for Lithium Ion Batteries.

Elucidating surface chemistry of Li4Ti5O12 anode material plays a critical role in solving gas evolution in Li4Ti5O12-based lithium ion batteries. Herein, we propose a CO2 cycloaddition reaction to study the surface chemistry of Li4Ti5O12 nanoparticles. Through the reaction, bare Li4Ti5O12 nanoparticles were demonstrated to have extensive Lewis-acid sites, that is, dangling Ti bonds or hydroxyl groups. Lewis-acid site is considered to be able to initiate the decomposition of electrolyte solvents and may also serve as one of the main reasons for gas evolution. TiNx coating layer is used to cover up the Lewis-acid site and is able to decrease yield of the cycloaddition reaction to some extent. These findings may provide a simple yet very effective way to evaluate surface chemistry and gas evolution in other lithium ion batteries, not limited to Li4Ti5O12-based batteries.