Processing and characterization of an Li₇La₃Zr_0.5Nb_0.5Ta_0.5Hf_0.5O₁₂ high-entropy Li–garnet electrolyte

In this paper, we demonstrated the processing of Li₇La₃Zr_0.5Nb_0.5Ta_0.5Hf_0.5O₁₂ (LLZNTH) high-entropy Li–garnet with promising properties for lithium batteries. We first synthesized the LLZNTH Li–garnet powders which have a single cubic garnet phase (space group: (Formula presented.); No. 230) without any secondary phases as well as uniform elements distributions. The prepared powders were further densified to a relative density of ∼94% with well-crystallized grains and good contact with the neighboring grains. Minimal grain growth can be observed in the sintering time range from 8 to 20 h, which is likely due to the sluggish effects of high-entropy compounds. The sample also maintains the cubic garnet phase along with uniform elements distribution after sintering. Electrochemical characterizations indicate that the densified sample has an adequate ionic conductivity of 4.67 × 10⁻⁴ S cm⁻¹ at room temperature, a low activation energy of 0.25 eV, and a low electronic conductivity in the order of 10⁻⁸ S cm⁻¹. The significance of designing high-entropy electrolyte is further discussed.