High Efficient Cellulose Nanofiber/Nano-SiO2 Separator for Sodium-Ion Batteries

Abstract

Sodium-ion batteries (SIB), with their relatively high energy density and good thermal stability, are currently attracting widespread attention. The separator is the key component of the SIB, which greatly affects the electrochemical performances and safety of the battery. Conventional polymer based separators cannot meet the requirements of the large scale application because of the high cost and poor thermal stability. Herein, the novel composite separators which are composed of cellulose nanofibers (CNFs) and nano-SiO2 by a simple slurry sieving process and paper making route were fabricated and utilized for the SIBs. The composite mass ratio are range from 100:0 to 40:60, and the composite separator exhibited excellent performance. As the content of nano-SiO2 reaches to 60%, the tensile strength and length at break are 5.73 MPa and 4.16%, respectively. The porosity, electrolyte, and ionic conductivity are 80.63%, 259.43% and 2.79 mS/cm, respectively. Importantly, the separators exhibited excellent electrolyte wetting property (contact angle almost reaches to 0), and can be heated at 200 °C for 2 hours without significant change. The assembled half SIB shows superior rate capacity and cycling performance (capacity retention of 96.5% after 100 cycles at 1C). The proposed fabrication of separators will play a significant contribution to sustainable development of renewable energy storage systems.