Experimental Corroboration of Lithium Orthothioborate Superionic Conductor by Systematic Elemental Manipulation

The Li superionic conductor Li3BS3 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 Li3BS3 has a 104 times lower ionic conductivity. Herein, we investigate the effect of a series of cation and anion substitutions in Li3BS3 SE on its ionic conductivity, including Li3–xM0.05BS3 (M = Cu, Zn, Sn, P, W, x = 0.05, 0.1, 0.2, 0.25), Li3–yBS2.95X0.05 (X = O, Cl, Br, I, y = 0.05, 0.1) and Li2.75–xP0.05BS3–xClx (x = 0.05, 0.1, 0.15, 0.2, 0.4, 0.6). Amorphous ionic conductor Li2.55P0.05BS2.8Cl0.2 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 Li2.55P0.05BS2.8Cl0.2 SEs show stable cycling with a discharge capacity retention of >97% after 200 cycles at 1C under 55 °C