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.