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

Abstract

In this paper, we demonstrated the processing of Li 7 La 3 Zr 0.5 Nb 0.5 Ta 0.5 Hf 0.5 O 12 (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: 𝐼𝑎 3𝑑; 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.

High‐Entropy Solid‐State Na‐Ion Conductor for Stable Sodium‐Metal Batteries

“…A Li 7 La 3 Zr 0.5 Nb 0.5 Ta 0.5 Hf 0.5 O 12 high-entropy garnet electrolyte exhibits a higher ionic conductivity of 4.67 × 10 À 4 S cm À 1 , further indicating that doping multi-elements in SEs can potentially improve the ion-conducting properties, modify the microstructures, and eventually expand the opportunities of designing and processing of such materials. [16] Along this line, based on previous research, the open structure of Na 5 MSi 4 O 12 provides sufficient possibilities of materials optimization and design by substituting the M sites by for instance In, Sc and the rare earths LuÀ Sm, to further improve the ionic conductivity. Furthermore, similar to the Li-ion conducting oxide highentropy materials, the high entropy approach stands a chance to not only stabilize the structure and increase the lattice disorder, but also affect the grain growth and morphology, so as to improve the ion-conducting performance of Na-SEs.…”

“…At the same time, the study shows that the high‐entropy SE is easier to enable relatively lower sintering temperature, and is beneficial to improve the density of the SE pellet. A Li 7 La 3 Zr 0.5 Nb 0.5 Ta 0.5 Hf 0.5 O 12 high‐entropy garnet electrolyte exhibits a higher ionic conductivity of 4.67×10 −4 S cm −1 , further indicating that doping multi‐elements in SEs can potentially improve the ion‐conducting properties, modify the microstructures, and eventually expand the opportunities of designing and processing of such materials [16] . Along this line, based on previous research, the open structure of Na 5 MSi 4 O 12 provides sufficient possibilities of materials optimization and design by substituting the M sites by for instance In, Sc and the rare earths Lu−Sm, to further improve the ionic conductivity.…”

Assessing Phase Stability in High-Entropy Materials by Design of Experiments: The Case of the (Mg,Ni,Co,Cu,Zn)O System

“…High-entropy oxides generally present five or more principal elements in near-equiatomic ratios and a configurational entropy of at least 1.609 R per mole of atoms . The first example of a HEO, Mg 0.20 Ni 0.20 Co 0.20 Cu 0.20 Zn 0.20 O, showed a rock salt (RS) structure and was followed by several other oxides presenting fluorite, − perovskite, − pyrochlore, − spinel, − and other crystal structures. − These materials aroused a great deal of interest because their ample compositional flexibility offers the possibility of introducing specific chemical elements into a crystal structure that generally does not allow to host them. This possibility often results in the appearance of new and unexpected functional properties.…”

High‐Entropy Cubic Perovskite Oxide‐Based Solid Electrolyte in Quasi‐Solid‐State Li–S Battery

“…[ 15 ] The substitution of higher valence cations such as V 5+ and Ti 4+ causes increased Li vacancies and improves the structural stability, [ 16 ] and lower valence cation such as Al 3+ can increase Li + concentration. Fu and Ferguson [ 17 ] synthesized a garnet‐type Li 7 La 3 Zr 0.5 Nb 0.5 Ta 0.5 Hf 0.5 O 12 that exhibited ionic conductivity of 4.67 × 10 −4 S cm −1 at room temperature, indicating that high‐entropy oxides could be potential solid‐state electrolytes for all‐solid‐state LSBs. Hao‐Yu Liu et al synthesized a high‐entropy oxide Li 6.4 La 3 Zr 0.4 Ta 0.4 Nb 0.4 Y 0.6 W 0.2 O 12 with an ionic conductivity of 1.16 × 10 −4 S cm −1 at 25 °C, which shows excellent electrochemical stability against Li metal at 0.1 mA cm −2 for 2 h. [ 18 ] Configurational entropy‐stabilized high‐entropy oxides have very low volume changes on lithiation/delithiation, which can potentially prevent Li‐ion transport failure originating from morphological decay of LLZO/cathode material interface.…”