Interconnected Porous Poly(ether imide) Separator for Thermally Stable Sodium Ion Battery
Xuhong Niu, Jing Li, Jianfeng Song, Yueming Li, Tao He
Abstract
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.