High-entropy NASICON-Type Li1.3Al0.4Ti0.5Zr0.5Sn0.5Ta0.1(PO4)3 with high electrochemical stability for lithium-ion batteries

Abstract

Li_1+xAl_xTi_2−x (PO₄)₃ (LATP) is a promising NASICON-type solid electrolyte for all-solid-state lithium-ion batteries (ASSLIBs) owing to its high ionic conductivity, low cost, and stability in ambient atmosphere. However, the electrochemical stability of LATP suffers upon contact with lithium metals, resulting in a reduction of Ti⁴⁺ to Ti³⁺ in its structure. This limitation necessitates interface modification processes, hindering its use in lithium-ion batteries. Herein, a high-entropy NASICON-type material, Li_1.3Al_0.4Ti_0.5Zr_0.5Sn_0.5Ta_0.1(PO₄)₃ (LATZSTP), is proposed to address the Ti-reduction issue, and the structural information was examined by extended X-ray absorption fine structure and neutron diffraction, revealing it to be a single phase of NASICON. The electrochemical stability is examined via cyclic voltammetry and Li stripping and plating tests; results indicate that LATZSTP has better stability against lithium metal than LATP does. Its ionic conductivity reaches 1.25 × 10⁻⁴ S cm⁻¹, an applicable ionic conductivity for lithium-ion batteries. Afterward, LATZSTP is incorporated into an ASSLIB. LiFePO₄/LATZSTP/Li has an initial capacity of 143 mA h/g and retention of 90.4 % after 100 cycles, which is better than LiFePO₄/LATP/Li, indicating the high potential of LATZSTP for its good electrochemical stability and ionic conductivity. The enhanced electrochemical stability demonstrates a new design method for LATP-type materials.