Effect of 65Li2O–27B2O3–8SiO2 glass addition on the phase composition, density, and conductivity of Li6.6Al0.05La3Zr1.75Nb0.25O12 films produced by tape casting

Thin-film solid electrolytes are crucial for safe high-energy all-solid-state power sources. The paper focuses on the issue of maintaining low porosity and high strength of solid electrolyte films obtained by tape casing. Ion-conducting glass is capable of filling the voids induced by heat treatment, creating a composite characterized by high ionic conductivity and enhanced mechanical strength. The effect of lithium borosilicate glass addition on the structure formation, morphology, and lithium-ion conductivity of Li_6.6Al_0.05La₃Zr_1.75Nb_0.25O₁₂ films is studied. The films based on the solid electrolyte were produced by tape casting on a Mylar substrate and then laminated together and pressed at room temperature to enhance their mechanical strength. The effect of the final sintering temperature on the electrical and physical characteristics of 65Li₂O–27B₂O₃–8SiO₂-free solid electrolyte films was studied. An increase of the sintering temperature from 900 to 1150 ℃ is accompanied by an expected increase in the ionic conductivity of the material from 2.1·10^–10 to 1.5·10^–7 S·cm⁻¹ at 25 ℃. An introduction of 3-wt. % 65Li₂O-27B₂O₃-8SiO₂ into the solid electrolyte resulted in the growth of total conductivity from 1.5·10^–7 to 3.5·10^–5 S·cm⁻¹ at room temperature. The thickness of the composite films after sintering varied from 50 to 70 μm. Such an approach to the modification of the solid electrolyte composition makes it possible to address two issues simultaneously, opening the prospects of creating composite solid electrolyte films with the best possible combination of mechanical strength and ionic conductivity to be used in all-solid-state batteries.