Enhanced lithium-ion battery separators via facile fabrication of sulfonated cellulose nanofiber

This study aims to develop a facile method for fabricating lithium-ion battery (LIB) separators derived from sulfonate-substituted cellulose nanofibers (CNFs). Incorporating taurine functional groups, aided by an acidic hydrolysis process, significantly facilitated mechanical treatment, yielding nanofibers suitable for mesoporous membrane fabrication via vacuum filtration. The fabricated separators exhibited an electrolyte uptake of approximately 200%, more than double that of commercial polyethylene separators, demonstrated excellent thermal stability even at temperatures exceeding 240 °C, and showed superior structural properties in FTC separators compared to TC separators. Sulfonate groups play a crucial role in inducing electrostatic repulsion between fibers, thereby enhancing ionic conductivity. This advancement resulted in a high electrochemical performance comparable to that of commercial separators, thus demonstrating its suitability for fast-charging applications in LIBs. This study highlights the pivotal role of sulfonate CNFs in producing high-performance LIB separators using a variety of eco-friendly functionalized biopolymers toward the development of high-performance sustainable energy storage materials.