Electrical properties of entropy-stabilized Li0.25La0.25NbO3 solid electrolyte ceramics

Oxide all-solid-state lithium batteries (ASSLBs) are promising candidates for next-generation energy storage due to their high energy density and enhanced safety. However, their commercial application is still hindered by the relatively low conductivity of solid electrolytes. To address this issue, a high-entropy strategy was employed to improve the conductivity of Li0.25La0.25NbO3 (LLNO). A series of entropy-stabilized solid electrolyte ceramics was synthesized via a conventional solid-state reaction method by co-doping five distinct cations (Ta5+, Hf4+, Zr4+, Ti4+, W6+) at the B-site of LLNO. XRD and SEM characterizations confirmed the formation of a perovskite structure in all synthesized samples, including the pristine LLNO, Li0.25La0.25Nb0.9(Ta0.02Hf0.02Zr0.02Ti0.02W0.02)O3 (LLNO-1), Li0.25La0.25Nb0.8(Ta0.04Hf0.04Zr0.04Ti0.04W0.04)O3 (LLNO-2) and Li0.25La0.25Nb0.7(Ta0.06Hf0.06Zr0.06Ti0.06W0.06)O3 (LLNO-3). AC-impedance and DCpolarization measurements demonstrated that the optimized composition of the sample LLNO-2 exhibited a conductivity of 4.68 × 10−6 S/cm and electronic conductivity of 5.30 × 10−8 S/cm with a low activation energy of 0.206 eV, representing a fourfold improvement over the pristine LLNO (conductivity 1.17 × 10−6 S/cm). Although the LLNO-3 ceramics showed the highest conductivity of 6.44 × 10−6 S/cm, it was associated with high activation energy of 0.218 eV and electronic conductivity of 1.28 × 10−7 S/cm. This work demonstrates that high-entropy strategy is a promising for enhancing the conductivity of perovskite-type solid electrolytes for ASSLBs.