Interconnected Porous Poly(ether imide) Separator for Thermally Stable Sodium Ion Battery

Due to the abundance and low costs of sodium resources, sodium ion batteries have attracted increasing attention for large-scale energy applications. The separator is one of the key materials that determines the performance of sodium ion batteries. Here a separator for sodium ion batteries is prepared using a thermally stable poly(ether imide) (PEI) and polyvinylpyrrolidone (PVP) blend via immersion phase separation. The PEI/PVP separators show an interconnected porous structure due to the secondary stage demixing of PVP and PEI polymers. The PEI/PVP separator demonstrated better wettability, higher ionic conductivity (1.14 mS cm–1), and higher thermal stability (up to 180 °C) compared to commercial polypropylene, and better flexibility and mechanical strength (39%, 6.7 MPa) compared to a glass fiber (GF) separator. The disordered mesoporous carbon/Na cell with a 16/12 PEI/PVP separator shows a high discharge capacity of 119.4 mAh g–1 at 0.5 C. Moreover, the cycling stability and rate performance of the sodium ion batteries is greatly enhanced using the prepared PEI/PVP as a separator. The enhanced electrochemical performance of the sodium ion batteries is attributed to the interconnected porous structure and high electrolyte uptake. These results suggest that the PEI/PVP separator is promising for safe and high performance sodium ion batteries.