Nanosized Li6PS5Cl Solid Electrolyte for All-Solid-State Lithium Batteries

Low active material proportion in composite cathodes limits the energy density of all-solid-state lithium batteries. Solid-phase synthesized sulfide electrolytes with large particles usually cause poor interfacial contact and impair active material utilization at high cathode loadings. Here, a stepwise liquid-phase method is employed to synthesize the Li6PS5Cl solid electrolyte. The resulting particles are smaller than 100 nm with an ionic conductivity of 2.4 mS cm-1, which optimizes ionic transport pathways within composite cathodes. Consequently, LiCoO2-based all-solid-state batteries incorporating liquid-phase-synthesized Li6PS5Cl (LPSC-LP) in composite cathodes outperform those with ball-milled Li6PS5Cl (LPSC-BM). At 80 and 90 wt % active material loadings, the LPSC-LP-based LiCoO2//Li cells exhibit initial discharge capacities of 106 and 86 mAh g-1 at 0.5 C, surpassing 85.5 and 54 mAh g-1 for LPSC-BM counterparts. Even at 95% loading, the LPSC-LP-based cell achieves 60.3 mAh g-1 at 0.5 C, far exceeding 27.3 mAh g-1 of the LPSC-BM-based cell.