Cryolithionite, with the formula Na 3 Al 2 Li 3 F 12 , is a unique natural mineral of the fluoride garnet group that occurs in hydrothermal deposits associated with minerals of other alumino-fluorides (e.g., Ivigtut, Greenland) . In the last several decades, some mineralogical and crystallographic efforts were undertaken to substitute Al in Na 3 Al 2 Li 3 F 12 by third-row transition metals, such as Fe, Co, Ni, Ti, V, Cr, as well as other elements, such as Sc, Ga, In, and Rh . Surprisingly, Cryolithionite has not received any attention for energy storage applications despite belonging to the garnet group, which is known to be one of the most promising groups of materials for solid electrolytes, e.g., La 3 Zr 2 Li 7 O 12 , used in Li-ion batteries today (see Fig. ) .