3-aminopropyltriethoxysilane-modified lithium tantalum phosphate -based composite solid electrolyte for lithium metal batteries

Polymer-ceramic composite electrolytes (CPEs) are a suitable option for all-solid-state batteries due to their high ionic conductivity and structural stability from ceramic components, as well as their structural flexibility and processability from polymer components. However, incompatibility of ceramic and polymer components causes aggregation of ceramic particles. Herein, LiTa₂PO₈(LTPO) is surface-modified with 3-aminopropyltriethoxysilane (APTES) for the first time to enhance interfacial compatibility with poly (vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) polymer electrolyte. Transmission Electron Microscope (TEM) observation reveals a uniform APTES coating layer (∼1.93 nm) is obtained on LTPO particles successfully. The APTES modification improves the dispersity of LTPO in PVDF-HFP. Additionally, APTES-modified LTPO-based CPE exhibits a significantly enhanced lithium-ion conductivity of 5.02 × 10−4 S cm−1 and a wide electrochemical window of 4.88 V vs. Li/Li+. The APTES-LTPO@CPE provides stable Li stripping/deposition behavior for 2640 h at 0.2 mAh cm−2 and 0.1 mA cm−2, while unmodified LTPO@CPE becomes unstable and short-circuited after 1470 h. The Li/APTES-LTPO@CPE/LiFePO₄ cell retains 80.1 % of capacity retention after 500th cycle, compared to only 35.5 % for unmodified LTPO@CPE after 425th cycle. The APTES surface modification effectively enhances LTPO dispersion, compatibility of LTPO with PVDF-HFP, and interfacial stability with Li metal anode, thereby improving overall electrochemical performances.