Improved Li ⁺ Transport and Interfacial Stability in PEO-LiTFSI Solid Electrolytes via Al ₂ O ₃ Ceramic Fillers at 20 °C

High Resolution Image Download MS PowerPoint Slide Incorporation of ceramic nanofillers (Al 2 O 3, SiO 2, TiO 2 ) into PEO-based solid electrolytes is investigated to compare their effects on Li + transport and address the low room-temperature conductivity of PEO by reducing polymer crystallinity and facilitating Li + migration through the amorphous phase. Among the tested fillers, 5 wt % Al 2 O 3 reduces membrane crystallinity by ≈ 11% and increases ionic conductivity by ≈1.8-fold. Comparative analysis suggests that Al 2 O 3 stands out due to possible interactions with PEO ether oxygens, as supported by structural and spectroscopic analyses. These interactions generate interconnected Li + transport pathways along polymer–filler interfaces, improving ionic conduction. Structural (XRD, FTIR, Raman) and thermal (TGA/DSC) analyses confirm an amorphous and thermally stable network. Electrochemical studies demonstrate that the Al 2 O 3 -containing membrane provides extended oxidation stability up to 5.22 V, with Li + transference number and diffusion coefficient 2.58 and 8 times higher than those of the filler-free PEO-LiTFSI system, respectively. This membrane displays reduced overpotential and an almost 100% recovery ratio after current-step cycling, emphasizing superior interfacial compatibility. Stable Li plating/stripping for ≈780 h at 50 μA cm –2 further confirms suppression of lithium dendrite growth, achieving a cycling lifetime 5.5 times longer. These findings highlight the role of Al 2 O 3 in promoting efficient low-temperature interfacial Li + conduction, offering promising insights for the design of solid polymer electrolytes.