Nanofiber matrix composite electrolyte for regulating ion distribution in fast kinetic sodium-ion batteries operating at wide temperatures

Abstract

Sodium-ion batteries (SIBs) address lithium-ion safety concerns but have lower energy density due to the larger ion, which can be alleviated by solid-state electrolytes (SSEs) but introduces challenges, such as reduced ionic conductivity at lower temperatures. A scalable electrospinning and quick UV-curing approach were used to fabricate a cost-effective ceramic nanofiber matrix composite electrolyte. The polymer segment chain contains carbonyl and ester groups that serve as Na+ hopping sites, while cationic ions on the ceramic SiO2 nanofiber (SNF) surface aid in anion fixation, resulting in a boosting sodium ionic conductivity (0.075 mS cm−1) even at −40 °C. Transverse abnormalities in the solid electrolyte cause unequal ion distribution and transport, which affects battery cycle performance. The three-dimensional SNF solves these problems, theoretically confirmed using COMSOL, resulting in 5400 h of steady plating/stripping at 5 mA cm−2. The half cell retains 90.2 % capacity after 1500 cycles at 26 °C and 0.5 C, while the pouch full cell has a 162.6 Wh kg−1 energy density and operates reliably from 0.2 to 15 C and −40 to 80 °C. This study provides insights for designing and applying SSEs in industrial-grade SIBs at various temperatures.