The Li superionic conductor Li 3 BS 3 has been theoretically predicted as an ideal solid electrolyte (SE) due to its low Li + migration energy barrier and high ionic conductivity. However, the experimentally synthesized Li 3 BS 3 has a 10 4 times lower ionic conductivity. Herein, we investigate the effect of a series of cation and anion substitutions in Li 3 BS 3 SE on its ionic conductivity, including Li 3- x M 0.05 BS 3 (M = Cu, Zn, Sn, P, W, x = 0.05, 0.1, 0.2, 0.25), Li 3- y BS 2.95 X 0.05 (X = O, Cl, Br, I, y = 0.05, 0.1) and Li 2.75- x P 0.05 BS 3- x Cl x ( x = 0.05, 0.1, 0.15, 0.2, 0.4, 0.6). Amorphous ionic conductor Li 2.55 P 0.05 BS 2.8 Cl 0.2 has a high ion conductivity of 0.52 mS cm -1 at room temperature with an activation energy of 0.41 eV. The electrochemical performance of all-solid-state batteries with Li 2.55 P 0.05 BS 2.8 Cl 0.2 SEs show stable cycling with a discharge capacity retention of >97% after 200 cycles at 1 C under 55 °C.