Abstract: Nanocellulose has attracted great attention as one of the most promising separator materials owing to the advantage of excellent electrolyte wettability and high thermal stability. It also has excellent natural abundance, biocompatibility and renewability. However, the dispersion of nanocellulose is inadequate, leading to self-agglomeration and other issues. This not only hinders the formation of a uniform porous separator but also diminishes the transport channels for Li+. To overcome this challenge, the rare earth ions Ce3+ were added. The complexation between the rare earth ions and the hydroxyl oxygen atoms of cellulose weakened the original hydrogen bond interactions among cellulose nanofibers, thereby enhancing the dispersion of CNF. In this work, a cerium-modified nanocellulose (0.050% Ce-CNF) separator with excellent thermal stability and high wettability using rare earth metal ions and cellulose nanofibers (CNF) as raw materials was prepared. Compared with conventional nanocellulose, the 0.05% Ce-CNF exhibited better processability for separator manufacturing and the separator obtained in this way possessed high stability in the electrolyte. The contact angle of 0.050% Ce-CNF separator with the electrolyte was smaller (18.7°) compared to that of polypropylene (PP) at 42.3°, and the ionic conductivity was higher. At the same time, due to the high porosity of 67.4% (compared to only 41.8% for the PP separator), batteries using CNF separators showed significantly improved rate performance compared to those using PP separators. In addition, the preparation process of Ce-CNF modified composite separator was environmentally friendly. Therefore, cerium-modified nanocellulose separator is expected to be a strong candidate for the next generation of high-safety and high-performance battery separators.

Key words: cellulose nanofibers, rare earth ion, hydrogen bonding network, composite separator, lithium batteries

摘要： 纳米纤维素具有环保、低成本、热稳定性高以及电解液浸润性好等特点，在锂电池隔膜领域受到广泛关注。本工作以稀土金属离子和纳米纤维素纤维(CNF)为原料，制备了一种具有优异热稳定性和高润湿性的铈改性纳米纤维素膜Ce-CNF。稀土离子通过对纳米纤维素纤维间氢键重构，调控纳米纤维间的氢键强度，显著改善了CNF分散性较差的问题。与常规纳米纤维素膜相比，使用铈改性的纳米纤维素膜组装的电池表现出更好的加工性和电性能。改性后的0.050% Ce-CNF隔膜与电解液接触角(18.7°)，相比于聚丙烯(PP)的42.3°更小，离子电导率更高。3 C倍率下比容量相比于PP隔膜提高13 mAh/g，且3 C倍率充电后再进行0.1 C倍率充电无容量损失。铈离子改性有效改善了纳米纤维素膜对锂电池电解液中的有机溶剂不耐受的问题，有希望成为下一代高安全和高性能电池隔膜的候选方案。

关键词: 纳米纤维素, 稀土离子, 氢键网络, 复合隔膜, 锂电池