Precise Cathode Interfacial Engineering for Enhanced Electrochemical and Thermal Stability of Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have continued achieving higher energy densities by utilizing various high-capacity, high-voltage cathode materials. However, they still show severe challenges regarding their reliability and electrolyte-cathode stability during operation especially at high-voltage charging that is needed to achieve higher energy density. Therefore, ensuring the stability of cathodes with electrolytes becomes much more critical for the safe and extended cycling of high-energy LIBs. Herein, we present a comprehensive investigation on maximizing cathode- electrolyte interfacial stability by employing a thin-film coating of various superionic single Li+ ceramic conductors on the commonly used lithium cobalt oxide (LCO) cathode. In the present investigation, the lithium aluminum germanium phosphate (Li1.5Al0.5Ge1.5(PO4)3; LAGP) ceramic electrolyte is found to be the best LCO surface stabilizer among commonly known ceramic conductors. The investigation of different synthesis parameters, such as the coating thickness, sintering temperature and time, annealing atmosphere, and so on, has been accomplished. The optimized performance has been obtained with an LAGP coating of a thickness of 0.6 wt % (LAGP amount) annealed at 830 degrees C for 1 h in a pure oxygen atmosphere. When cycled in a voltage window of 3-4.3 V, 0.6 wt % LAGP on the LCO cell shows a discharge capacity of 180.87 and 163.91 mAh/g at 0.2 and 4C, respectively; in comparison, a pure LCO-based LIB shows 149.82 and 78.90 mAh/g at 0.2 and 4C. Furthermore, LAGP-coated LCO-based LIBs when compared to the pristine LCO-based LIBs show (i) remarkably better thermal stability, (ii) lower voltage polarizations during cycling, and (iii) an enabled higher voltage charge of up to 4.8 V.