Preparation of lithium ion conductive Li₆PS₅Cl solid electrolyte from solution for the fabrication of composite cathode of all-solid-state lithium battery

An argyrodite type Li₆PS₅Cl was prepared by the solution process using a mixture of solvents with a fast evaporation rate. The crystal phase and ionic conductivity of the Li₆PS₅Cl solid electrolyte were examined by X-ray diffraction and electrochemical impedance spectroscopy, respectively. Li₆PS₅Cl derived from solution process shows an argyrodite structure with an ionic conductivity of 6 × 10^-5 S cm⁻¹ at room temperature. Composite cathode was directly prepared by dispersing LiNi_1/3Mn_1/3Co_1/3O₂ (84 wt%) and a conductive additive (2 wt%) into a Li₆PS₅Cl precursor solution (14 wt%), with subsequent heating at 150 °C. Morphology of the composite cathode was evaluated by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The formation of Li₆PS₅Cl-layer on the active material particles was observed. A bulk-type all-solid-state cell was fabricated with composite cathode derived from the solution process, achieving an initial discharge capacity of 160 mAh g⁻¹ and capacity retention of ~80% after 20 cycles with a capacity efficiency of 100%.