Paperator: The Paper-Based Ceramic Separator for Lithium-Ion Batteries and the Process Scale-Up Strategy

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.