Reaction environment as a driver of the phase evolution and lithium storage performance of lithium titanium oxide

Abstract

Spinel-structured Li4Ti5O12 (s-LTO) has garnered significant attention as an alternative to graphite in lithium-ion batteries. However, conventional solid-state synthesis of s-LTO faces significant challenges in achieving phase purity. The process is highly sensitive to the Li/Ti stoichiometry, demanding meticulous control of the lithium and titanium precursor ratio. While extensive research has focused on understanding the formation mechanism of s-LTO, the influence of the reaction environment on phase evolution and electrochemical performance has been largely overlooked. This work unveils a critical role for the reaction environment in optimizing s-LTO synthesis. We demonstrate a high degree of sensitivity in the extent of Li sublimation during the solid-state reaction to the specific furnace and gas employed. The Li sublimation creates conditions with a lower lithium concentration, which favors the formation of ramsdellite-structured Li2Ti3O7 (r-LTO), ultimately resulting in a mixture of LTO phases. The incorporation of mixed LTO phases presents a trade-off in battery performance. While the co-existence of r-LTO with s-LTO can mitigate capacity fade at high charge rates, the concomitant formation of the electrochemically inactive Li2TiO3 phase significantly hinders this advantage. Therefore, suppressing Li2TiO3 formation is vital to fully exploit the advantages of s-LTO/r-LTO composite electrodes. This newfound understanding holds significant promise for the battery industry, especially for the growing demand for LTO batteries in consumer electronics. © 2024 Elsevier B.V.