All-solid-state lithium batteries based on sulfide solid electrolytes are potential candidates for large-scale energy storage applications. Here, composite cathode with high content of an active material was prepared by a liquid phase process assisted by a dispersant agent to produce a better electrode and electrolyte interface. Li₆PS₅Cl sulfide electrolyte derived from a solution containing dispersant showed an argyrodite crystal phase with a better distribution of particle size and higher conductivity compared with those without dispersant. Regular distribution of Li₆PS₅Cl particles in nanometric scale with a spherical shape below 500 nm and conductivity of 0.6 × 10⁻³ S cm⁻¹ (ρ = 1.40 g cm⁻³) at room temperature were obtained. Composite cathode was prepared by the dispersion of LiNi_1/3Mn_1/3Co_1/3O₂ particles and carbon additive in the Li₆PS₅Cl-solution containing dispersant agent and subsequent drying at 180 °C. Bulk-type all-solid-state battery fabricated with the composite cathode containing 89 wt% of the active material showed an initial discharge capacity of 110 mA h g⁻¹ at 25 °C and maintained 95% discharge capacity after 15 cycles.