An easily degradable composite separator with high affinity to ionic-liquid-based electrolytes for safe Li-ion batteries

Ionic-liquid-based electrolytes emerge as a viable alternative to commercial carbonate electrolytes due to their superior stability and safety, especially at high temperatures. However, their affinity to the currently widely used polyolefin-based separators is poor. Herein, an economical and environmentally friendly separator composed of hydroxyapatite and cellulose nanofibers is designed and fabricated. The composite separator possesses a fibrous network with a large surface area and rich polar groups, featuring high wettability and ionic conductivity based on carbonate and ionic-liquid-based electrolytes. The LiFePO4/Li half-cell with this separator exhibits superior cyclability with a high capacity of similar to 130 mAh g(-1) using an ionic-liquid electrolyte at room temperature. Moreover, the resulting composite separator is thermally stable, and the assembled batteries achieve outstanding cyclability at 80 degrees C. Furthermore, the universality of the separator is demonstrated by successful employment in sodium and zinc-ion batteries. The as-fabricated composite separator is easily degradable and promising as an environmental-benign substitute to conventional polyolefin-based separators for next-generation batteries.

Automated summary

Ionic-liquid-based electrolytes are considered as a promising alternative to commercial carbonate electrolytes due to their superior stability and safety at high temperatures. However, their poor compatibility with polyolefin-based separators hinders their application. In this study, an economical and environmentally friendly separator composed of hydroxyapatite and cellulose nanofibers is developed. It exhibits high wettability and ionic conductivity with carbonate and ionic-liquid-based electrolytes, and shows excellent cyclability and thermal stability in LiFePO4/Li half-cell, sodium-ion batteries, and zinc-ion batteries.