Suppressing Ti Reduction Via Multiple Doping in Nasicon-Type Solid Electrolyte

The NASICON-type solid electrolyte emerges as a promising candidate for lithium-ion batteries due to its notable ionic conductivity and stability in ambient conditions. However, the LiTi 2 (PO 4 ) 3 and LiGe 2 (PO 4 ) 3 series encounter a reduction of Ti and Ge upon contact with lithium metal, limiting their use in all-solid-state lithium-ion batteries. To address this challenge, we propose a solution by introducing multi-doped NASICON-type oxides. Following the doping process, the material demonstrates electrochemical stability when in contact with lithium metal, as evidenced by cyclic voltammetry measurements. Moreover, the material achieves a noteworthy ionic conductivity of ca. 1.3 × 10 -4 S/cm, rendering it suitable for integration into lithium-ion batteries. By resolving the reduction issue of Ti in the material, it becomes feasible to employ it in all-solid-state lithium-ion batteries without the need for a protective layer between lithium metal and the solid electrolyte. This absence of an additional layer reduces interfacial resistance within the device, thereby anticipating improved battery performance.