Sb-based lithium sulfide electrolytes are promising for all-solid-state lithium battery applications due to their ultrahigh Li-ion conductivity (10⁻² S/cm) which is even comparable to current liquid electrolytes. However, the poor electrochemical stability between this electrolyte and high voltage layered structure cathode makes it difficult to achieve excellent battery performances. Herein, Li_6.5Sb_0.5Ge_0.5S₅I electrolyte with ionic conductivity up to 10 m S/cm is successfully synthesized and the electrochemical failure mechanism of the corresponding battery using bare LiNi_0.6Mn_0.2Co_0.2O₂ cathode and Li-In anode is revealed. Furthermore, Li₃InCl₆ electrolyte is introduced both as an ionic additive in the cathode mixture and as an isolating layer to avoid side reactions. The designed configuration delivers a high discharge capacity of 162.7 mAh/g at 0.5C and sustains 74.5% of the capacity after 200 cycles at room temperature. Moreover, it also can reversibly cycle from -20 to 60 °C with superior battery performances. This work provides a general design strategy for utilizing highly conductive sulfide electrolytes with low stability in all-solid-state batteries.