Efficient utilization of glass fiber separator for low-cost sodium-ion batteries

The separator is a key component of sodium-ion battery, which greatly affects the electrochemical performances and safety characteristics of the battery. Conventional glass fiber separator cannot meet the requirements of large-scale application because of high cost and poor mechanical properties. Herein, the novel composite separators are prepared by a simple slurry sieving process using glass fiber separator scraps and ordinary qualitative filter paper as raw materials. As the composite mass ratio is 1:1, the composite separator has excellent comprehensive properties, including tensile strength of 15.8 MPa, porosity of 74.3%, ionic conductivity of 1.57 × 10⁻³ S·cm⁻¹ and thermal stability at 210°C. The assembled sodium-ion battery shows superior cycling performance (capacity retention of 94.1% after 500 cycles at 1C) and rate capacity (retention rate of 87.3% at 10C), and it maintains fine interface stability. The above results provide some new ideas for the separator design of high-performance and low-cost sodium-ion batteries.