Nanoporous Regenerated Cellulose Separator for High-Performance Lithium Ion Batteries Prepared by Nonsolvent-Induced Phase Separation

Cellulose-based separators for lithium ion batteries have attracted much attention due to the good wettability and thermal stability. However, most of them are based on the expensive nanocellulose, cellulose derivatives, or toxic chemicals. Here, a novel nanoporous regenerated cellulose separator (RCS) was prepared from common cotton pulp by a nonsolvent-induced phase separation (NIPS). In particular, the whole process of the phase separation was eco-friendly. Ethanol at different temperatures was used as the nonsolvent to regenerate the cotton pulp cellulose solution dissolved in NaOH/urea/water. The study of the phase separation mechanism shows that the low solubility of nonsolvent to urea is the critical factor to form nanoporous structure for a cellulose alkali/urea/water solvent system. Equally important, the obtained RCSs not only have excellent physical properties, but also exhibit higher electrochemical performance than the commercial Celgard2325. This work provides a feasible choice for the preparation of a high-performance cellulose-based separator.