Sustainable APTES-Modified Nano-TiO2/PVA Composite Nanofibrous Separators for Thermally Stable Lithium-Ion Battery

Commercial separators face several significant challenges that must be addressed before they can be used effectively in high-energy-density batteries. These issues include low porosity, poor electrolyte wettability, and inadequate dimensional stability. To address these challenges, 3-aminopropyltriethoxysilane (APTES)-modified nano-TiO₂ (MNT) with improved dispersion and interfacial compatibility, an isocyanate-based cross-linker and poly(vinyl alcohol) (PVA) as a spinning solution component are used to prepare the electrospun nanofibrous separator in this work. The obtained MNT/PVA separator demonstrates superior performance, including high mechanical strength (33.2 MPa), excellent thermal dimension stability (with no shrinkage at 200 °C), high porosity (82.5%), substantial electrolyte uptake (566.1%), and outstanding ionic conductivity (1.54 mS cm⁻¹). Moreover, when applied in button cell batteries, the MNT/PVA separator retains more than 88.3% of its initial capacity (137.9 mAh g⁻¹) after 100 cycles at 0.5C. This performance surpasses that of conventional PVA and Celgard separators, suggesting that the MNT/PVA separator has a great potential to replace commercial counterparts in advanced lithium-ion batteries.