No abstract

Due to its flexibility, cost-effectiveness, and natural abundance, paper has become a material of choice for its targeted applications in electronic and optoelectronic devices. With an aim to develop a paper-based ceramic separator (henceforth will be referred to as paperator), a low-cost paper substrate sourced from the local market has been functionalized by the wet-coating method using duo-polymer (chitosan and polyvinyl alcohol) and ceramic (BaTiO3) nanopowder. The developed paperator shows excellent air permeability, improved thermal stability of up to 200 °C without dimensional shrinkage, quicker wettability to an electrolyte, and comparable electrochemical performance to that of polypropylene-based commercial separator. The modification of the paper substrate using polymer and ceramic particles has also improved the tensile strength of the paperator to a maximum value of 45.23 MPa w.r.t. 28.20 MPa for pristine paper. The electrochemical performance of the developed paperators shows satisfactory cell performance at different current densities with excellent coulombic efficiency and comparable discharge capacities with that of a commercial separator. Compared to the commercial PP-based membrane, slightly lowered discharge capacities are obtained from the cells fabricated with developed paperators, which may primarily be due to the higher thickness (60/70 μm) and cellulosic tortuosity. Electrochemical performances of the developed “paperators” were also evaluated for use in supercapacitors (SCs) by fabricating SC cells and their testing as per IEC 62391-1, which showed the cell capacitance and ESR values of 17.2 ± 0.8 F and 76 ± 3 mΩ, respectively, and the results were also compared with those of commercial cellulose-based paper separators. Based on the R&D achievements, the present study has also been extended for a scale-up strategy to produce a paper-based separator in roll form, where a “paperator” of 60 mm in width in a continuous manner has been fabricated by using in-house-designed semi-automated double-decker separator fabricator machine.

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.