Ionic selectivity is of significant importance in both fundamental science and practical applications. For instance, an ion-selective material allows the passage of a particular kind of ions while blocking the others, which could be used for purification of materials. Herein, the Li-ion-selectivity of a garnet-type solid electrolyte is discussed by comparing the difference of activation energy between different ions migrating in solids. The high ion-selectivity is confirmed by harvesting high-purity metallic lithium (99.98 wt%) from low-lithium-purity sources (80 wt%) at a moderate temperature (190 ℃). This gives it huge potential in separating lithium with impurities especially alkali and alkali-earth elements. The cost of metallic lithium production is only 25% of the international lithium price. The proposed electrochemical metallic lithium separating method is advantageous compared with the traditional process in terms of efficiency, safety, and cost.

The lithium dendrite and parasitic reactions are two major challenges for lithium (Li) metal anode—the most promising anode materials for high-energy-density batteries. In this work, both the dendrite and parasitic reactions that occurred between the liquid electrolyte and Li-metal anode could be largely inhibited by regulating the Li⁺-solvation structure. The saturated Li⁺-solvation species exist in commonly used LiPF₆ liquid electrolyte that needs extra energy to desolvation during Li-electrodeposition. Partial solvation induced high-energy state Li-ions would be more energy favorable during the electron-reduction process, dominating the competition with solvent reduction reactions. The Li-symmetric cells that are cycling at higher temperatures show better performance; the cycled lithium metal anode with metallic lustre and the dendrite-free surface is observed. Theoretical calculation and experimental measurements reveal the existence of high-energy state Li⁺-solvates species, and their concentration increases with temperature. This study provides insight into the Li⁺-solvation structure and its electrodeposition characteristics.