After its initial success with metals, Rost \textit{et al}. ^[1] discovered that the concept of combining multiple
elements in equimolar ratio also works for oxide materials. If multiple suitable cations or anions are
incorporated on the same sublattice in equimolar amount, the configurational entropy of the material
increases. When the entropy term in the Gibbs free energy formula gets big enough, solid solutions can
form, which makes many new compositions accessible.

The strong composition-structure-property relationship in oxide materials makes the use of five or more
elements on the cationic sublattices very appealing. They can influence many characteristics such as
electric, ionic, and thermal conductivity, mechanical strength and optical properties and offer a wide
design space of new materials for various applications. Since the used elements can show synergistic
effects, it further increases the viability of this synthesis strategy. Using these effects on increasing Li-ion
conductivity and storage may enable the creation of new, sought after battery materials. ^[2]

One system, which is being researched as a new solid-state electrolyte for all-solid lithium batteries are
Li-garnets due to their promising properties. It is compatible with metallic lithium, has a wide
electrochemical stable window (4 - 5 V) and in its high temperature cubic phase it exhibits competitive
ionic conductivities of 10^-4 – 10^-3 $S \cdot $cm^-1. Li-garnets are known to be able to accommodate many
different cations on its sublattices which makes it possible to tailor the properties to the planned
application. ^[3] In this work high-entropy garnets have been synthesized through the solid-state and the
co-precipitation route involving multiple cations. The phase analysis was done with powder X-ray
Diffraction, the chemical composition was studied via Scanning Electron Microscopy and Energy
Dispersive Spectroscopy. Electrochemical properties were characterized by Electrochemical Impedance
Spectroscopy. Even though the microstructure was not optimized, first results within the order of
10^-4 $S \cdot $cm^-1 were obtained.

References
[1] C. M. Rost \textit{et al}., \textit{Nature Communications}, \textbf{2015}, \textit{6}, 8485
[2] A. Sarkar \textit{et al}., \textit{Scripta Materialia}, \textbf{2020}, \textit{187}, 43-48
[3] Z. Xu \textit{et al}., \textit{Journal of Materiomics}, \textbf{2023}, \textit{9}, 651-660