Enhancing ionic conductivity and structural stability of LiTa₂PO₈ through Sc³⁺ doping

Abstract

LiTa₂PO₈ (LTPO) is a novel inorganic ceramic electrolyte that has garnered significant attention due to its high ionic conductivity. However, in all‐solid‐state battery systems, the tantalum (Ta) within the crystal structure of this electrolyte is prone to reduction by lithium at the anode, resulting in the conversion of Ta⁵⁺ to Ta³⁺ and Ta²⁺. This reduction induces instability in both the structural integrity and performance of the electrolyte, thereby adversely affecting the cycling performance of solid‐state batteries. To improve the stability of the crystal structure, large‐radius scandium (Sc³⁺) ions were introduced into LTPO. The results demonstrate that Sc³⁺ ions can effectively replace some of the Ta⁵⁺ sites within the structure, thereby altering the crystal framework and increasing the unit cell volume. The incorporation of Sc³⁺ ions not only promotes the growth of LTPO crystals but also enhances grain connectivity. This modification expands the pathways for lithium‐ion transport, thereby significantly enhancing the room temperature ionic conductivity of LTPO. The synthesized Li_1.08Ta_1.96Sc_0.04PO₈ exhibits an impressive ionic conductivity of 5.12 × 10⁴ S/cm. Furthermore, lithium symmetric cells fabricated from Li_1.08Ta_1.96Sc_0.04PO₈ demonstrate exceptional cycling stability, underscoring the potential of this doped material for practical applications in energy storage systems.