Preparation and characterization of glass solid electrolytes in the pseudoternary system Li3BO3-Li2SO4-Li2CO3

The ternary oxide glasses in the system of Li3BO3-Li2SO4-Li2CO3 were prepared by mechanical milling. By heating the glasses to crystallize, the glass-ceramics were obtained. The 90Li3BO3·7Li2SO4·3Li2CO3 (mol%) glass-ceramic electrolyte showed the conductivity of 1.0 × 10− 5 S cm− 1 at room temperature, which was higher than that of the 90Li3BO3·10Li2SO4 glass-ceramic electrolyte. At the 33Li3BO3·33Li2SO4·33Li2CO3 composition, a cold-pressed pellet at 720 MPa of the glass exhibited excellent formability with the relative density of 90%, which was comparable to that of sulfide glass electrolytes. By heating the glass, a metastable phase was precipitated and the glass-ceramic exhibited the conductivity of 1.8 × 10− 6 S cm− 1 at room temperature. To obtain a denser pellet, hot-pressing at around its glass-transition temperature and consecutive crystallization were conducted. The hot-pressed pellet of the glass-ceramic was transparent and showed the conductivity of 2.3 × 10− 6 S cm− 1 at room temperature. From the ultrasonic pulse-echo measurement, the bulk modulus of the glass was 44 GPa, which was lower than that of 68 GPa of the 90Li3BO3·10Li2SO4 glass. From the galvanostatic cycling test, the 33Li3BO3·33Li2SO4·33Li2CO3 glass-ceramic electrolyte was kinetically stable against lithium metal negative electrode. The 33Li3BO3·33Li2SO4·33Li2CO3 glass-ceramic electrolyte is therefore a promising material with both conductivity and ductility for the application to all-solid-state batteries.