A novel membrane based on cellulose acetate nanofibers with a ZrO2 reinforcement layer for advanced sodium-ion batteries

A novel ZrO2-reinforced nanofibrous membrane for sodium-ion batteries was synthesized via fabricating a ZrO2-reinforced layer on the surface of the modified cellulose acetate membrane (MCA) by a new and simple in-situ chemical precipitation method. Upon the rational design, the ZrO2-reinforced nanofibrous membranes exhibit high chemical stability and excellent wettability (a decreased contact angle from 26.8° to 7.4°) in electrolytes. Moreover, the ZrO2-reinforced nanofibrous membranes also show no distinct dimensional change after being kept at 250 °C for 30 min and high tensile strength up to 1.15 MPa. Compared to that of the MCA membrane (1.61 mS cm−1), the ZrO2@MCA-0.5h (immersed in a ZrO(NO3)2 solution for 0.5 h) exhibits a high ionic conductivity of 2.23 mS cm−1. Additionally, the cell with the ZrO2@MCA-0.5h displays a high discharge capacity of 224.8 mAh g−1 at 0.5 C, which are higher than those of the MCA membrane (156.1 mAh g−1). Meanwhile, the rate performance of the cells assembled with the ZrO2-reinforced nanofibrous membranes, especially with the ZrO2@MCA-0.5h membrane，are also better than that of the MCA. All the above improvements can be attributed to the presence of the continuous-phase ZrO2 reinforcement layer fabricated on the surface of the MCA membrane, which forms a strong self-adhesive structure among fibers to enhance mechanical strength and has a good affinity for the electrolyte to obtain high ionic conductivity.