Optimization of Annealing Process of Li₆PS₅Cl for All-Solid-State Lithium Batteries by Box-Behnken Design

Li6PS5Cl possesses high ionic conductivity and excellent interfacial stability to electrodes and is known as a promising solid-state electrolyte material for all-solid-state batteries (ASSBs). However, the optimal annealing process of Li6PS5Cl has not been studied systematically. Here, a Box-Behnken design is used to investigate the interactions of the heating rate, annealing temperature, and duration of annealing process for Li6PS5Cl to optimize the ionic conductivity. The response surface methodology with regression analysis is employed for simulating the data obtained, and the optimized parameters are verified in practice. As a consequence, Li6PS5Cl delivers a rather high conductivity of 4.45 mS/cm at 25 C-degrees, and ASSB consisting of a LiNi(0.6)Co(0.2)Mn(0.2)O(2 )cathode and lithium anode shows a high initial discharge capacity of 151.7 mAh/g as well as excellent cycling performances for more than 350 cycles, highlighting the importance of the design of experiments.