High-entropy NASICON-Type LiAlTiZrSnTa(PO) with high electrochemical stability for lithium-ion batteries.

LiAlTi (PO) (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 Ti to Ti in its structure. This limitation necessitates interface modification processes, hindering its use in lithium-ion batteries. Herein, a high-entropy NASICON-type material, LiAlTiZrSnTa(PO) (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 S cm, an applicable ionic conductivity for lithium-ion batteries. Afterward, LATZSTP is incorporated into an ASSLIB. LiFePO/LATZSTP/Li has an initial capacity of 143 mA h/g and retention of 90.4 % after 100 cycles, which is better than LiFePO/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.