Enhancement of electrochemical performance of lithium-ion battery by single-ion conducting polymer addition in ceramic-coated separator

Single-ion conducting polymers have been widely reported in the literature as solid polymer electrolytes, but their low ionic conductivity has limited industrial applications at ambient temperature. Here, we employed a perfluoroalkyl sulfonamide-based single-ion conducting polymer-lithiated poly(perfluoroalkylsulfonyl)imide (LiPFSI) to promote the migration of free Li-ions and diminish cell polarization in lithium-ion batteries. After blending with Al₂O₃ powder, the LiPFSI/Al₂O₃ composite was coated on a commercial polyethylene separator. Adding the high surface energy of Al₂O₃ particles and the exceptional ionic conductivity of LiPFSI resulted in a LiPFSI/Al₂O₃ composite-coated separator with excellent wettability and low impedance. A LiFePO₄/Li half-cell with this separator showed a highly improved charge–discharge cyclability up to 130 mAh/g that maintained 98% retention of the original reversible capacity after 220 charge–discharge cycles at a high current rate of 2 C (1 C = 170 mAh/g). Even at a high rate of 5 C, the cell capacity could be maintained above 100 mAh/g. Herein, we present a simple and effective method to optimize the separator with the LiPFSI/Al₂O₃ composite and thus improve the high rate charge–discharge performance of Li-ion batteries.