A detailed characterisation study of Li6PS5Cl ionic conductors from several synthetic routes

Abstract

Studies of argyrodite Li6PS5Cl as solid electrolyte are increasing, motivated by its high ionic conductivity and its easy processability. However, development of All-Solid-State-Batteries lies on the ability to produce such compound with a good purity. This work presents the characterization results of different argyrodite grades: commercial and homemade one. In parallel, synthesis of Li6PS5Cl from Li4P2S7 precursor is reported for the first time. The purity effect on these properties will be explored by using X-ray diffraction coupled with Raman spectroscopy and electrochemical impedance spectroscopy techniques. Crystal properties investigations will be particularly conducted, given that smaller crystallite sizes would lead to an enhanced ionic percolation network by increasing the microstructure homogeneity in catholyte. Such SE could be obtained only by avoiding a post synthesis annealing treatment. Finally, electrochemical properties of the different reported grades will also be discussed in this study. We demonstrate here 1. the beneficial effect of Li4P2S7 to obtain a pure sulfur-based solid electrolyte with nanometric crystallites without solid state synthesis and 2. the impact of impurities on its ionics and electrochemical properties.