Capacity Loss Mechanism of the Li4Ti5O12 Microsphere Anode of Lithium-Ion Batteries at High Temperature and Rate Cycling Conditions

Li4Ti5O12 (LTO) as the anode of lithium (Li) ion batteries has high interfacial side reactivity with the electrolyte, which leads to severe gassing behavior and poor cycling stability. Herein, the capacity loss mechanism of the high-tap density LTO microsphere anode under different temperatures (25, 45, and 60 degrees C) and charge/discharge rates (1 and 5 C) is systematically investigated. The capacity retentions of the LTO/Li cell after 500 cycles at 1 C are 95.6, 90.0, and 87.1% under three temperatures, which drop to 91.9, 58.3, and 20.9% when cycling at 5 C, respectively. Results show that the high temperature and rate almost do not damage the structure of LTO, but greatly affect the thickness and components of the solid electrolyte interface (SEI), and consequently reduce the performance of the LTO/Li cells. An SEI mainly consisting of inorganic species forms on LTO after 500 cycles at 1 C, while organic compounds are observed after 500 cycles at 5 C. The capacity of cycled LTO cannot recover again because of the thick SEI although using new Li metal anodes, separators, and electrolytes. This work demonstrates that it is of great significance for LTO to construct a stable SEI for achieving excellent cycling performance at a high rate and temperature.