Nanofibrillated Cellulose (NFC) as a Pore Size Mediator in the Preparation of Thermally Resistant Separators for Lithium Ion Batteries

Battery separators play a vital role in the safety, sustainability, and electrochemical performance of lithium ion batteries (LIBs). In this work, thermally resistant composite membranes were fabricated by a wet-laid process using northern bleached softwood kraft (NBSK) fibers, polysulfonamide (PSA) fibers, and nanofibrillated cellulose (NFC), for lithium ion battery applications. NFC functioned as a mediator to control and optimize pore size in the composite membranes, while the PSA fibers provided superior heat resistance to the membranes. The as-prepared composite separator membranes have more uniform micropores and superior thermal stability and electrolyte absorption in comparison with a commercial separator membrane (Celgard 2350).