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).