Advanced Sustainable Trilayer Cellulosic "Paper Separator" Functionalized with Nano-BaTiO₃ for Applications in Li-Ion...

In the quest of developing a sustainable, low-cost and improved separator membrane for application in energy storage devices like lithium-ion batteries (LIBs) and supercapacitors (SCs), here we fabricated a trilayer cellulose-based paper separator engineered with nano-BaTiO₃ powder. A scalable fabrication process of the paper separator was designed step-by-step by sizing with poly(vinylidene fluoride) (PVDF), thereafter impregnating nano-BaTiO₃ in the interlayer using water-soluble styrene butadiene rubber (SBR) as the binder and finally laminating the ceramic layer with a low-concentration SBR solution. The fabricated separators showed excellent electrolyte wettability (216-270%), quicker electrolyte saturation, increased mechanical strength (43.96-50.15 MPa), and zero-dimensional shrinkage up to 200 °C. The electrochemical cell comprising graphite|paper separator|LiFePO₄ showed comparable electrochemical performances in terms of capacity retention at different current densities (0.05-0.8 mA/cm²) and long-term cycleability (300 cycles) with coulombic efficiency >96%. The in-cell chemical stability as tested for 8 weeks revealed a nominal change in bulk resistivity with no significant morphological changes. The vertical burning test as performed on a paper separator showed excellent flame-retardant property, a required safety feature for separator materials. To examine the multidevice compatibility, the paper separator was tested in supercapacitors, delivering a comparable performance to that of a commercial separator. The developed paper separator was also found to be compatible with most of the commercial cathode materials such as LiFePO₄, LiMn₂O₄, and NCM111.