Zr- and Ce-doped Li₆Y(BO₃)₃ electrolyte for all-solid-state lithium-ion battery

The ionic conductivity of Li₆Y(BO₃)₃ (LYBO) was enhanced by the substitution of tetravalent ions (Zr⁴⁺ and Ce⁴⁺) for Y³⁺ sites through the formation of vacancies at the Li sites, an increase in compact densification, and an increase in the Li⁺-ion conduction pathways in the LYBO phase. As a result, the ionic conductivity of Li_5.875Y_0.875Zr_0.1Ce_0.025(BO₃)₃ (ZC-LYBO) reached 1.7 × 10^-5 S cm^-1 at 27 °C, which was about 5 orders of magnitude higher than that of undoped Li₆Y(BO₃)₃. ZC-LYBO possessed a large electrochemical window and was thermally stable after cosintering with a LiNi_1/3Mn_1/3Co_1/3O₂ (NMC) positive electrode. These characteristics facilitated good reversible capacities in all-solid-state batteries for both NMC positive electrodes and graphite negative electrodes via a simple cosintering process.