Integrating cellulose nanofibers and hyperbranched polymer electrolyte as separator of lithium-ion battery with high capacity and safety.

In response to escalating global demands for sustainable technologies, the development of high-performance, safe, and eco-friendly separators of lithium-ion battery have become imperative. Herein, a novel nanocellulose composite aerogel separator (designated TOCN-LiP) was engineered through non-covalent crosslinking between TEMPO-oxidized cellulose nanofibers (TOCN) and a well-designed hyperbranched polymer lithium salt electrolyte (denoted LiP). The TOCN-LiP separator demonstrated enhanced interfacial compatibility with lithium metal anodes and exhibited comprehensive performance improvements compared with original TOCN separators. Notably, the TOCN-LiP-10 architecture displayed a homogeneous three-dimensional porous structure, coupled with exceptional cycling stability and a lithium-ion transference number of up to 0.71, achieving a discharge capacity of 125.1 mA h g-1 after 100 cycles at 0.5C, whereas Celgard2500 achieved only 75.2 mA h g-1. Furthermore, the TOCN-LiP-10 separator demonstrated excellent thermal stability, maintaining dimensional integrity at 200 °C, along with enhanced safety characteristics absent in commercial separators. By preparing aerogel separators through facile LiP molecular synthesis and its incorporation into TOCN matrix for optimized lithium-ion transport, this work provides an in-depth insight into developing sustainable, safe, and high-performance LIB separators.