Flame retardant polyurethane acrylate solid polymer electrolyte based on the synergistic effect of modified halloysite nanotubes for safe lithium batteries

Abstract

The practical application of polyurethane acrylate solid electrolytes is restricted by their flammability and inadequate of ion transportation performance. Herein, a novel flame retardant solid polymer electrolyte membrane was successfully designed through UV light curing phosphorus-containing polyurethane acrylate prepolymer, modified halloysite nanotubes and lithium salt. The FR-SPE1 electrolyte mainly composed of flame retardant polyurethane acrylate (FR-PUA) prepolymer, 20 wt% lithium bis-(trifluoromethanesulfonyl)imide) (LiTFSI) along with 5 wt% acid modified halloysite nanotubes(A-HNTs), which possesses excellent P-Al-Si synergistic flame retardancy with the limiting oxygen index (LOI) value of 39.2%, and the vertical burning test can reach the V-0 level of UL 94 standard. Meanwhile, FR-SPE1 electrolyte exhibits strong mechanical strength and electrochemical stability, which extends the electrochemical window to 4.88 V (vs. Li+/Li). Interestingly, A-HNTs can also effectively enhance the dissociation degree of lithium salts in polymers, which is conducive to improve the lithium ion transport performance. Moreover, the cell fabricated by lithium iron phosphate (LiFePO4), FR-SPE1 and Li anodes evinces benign cycling performance (156.6 mAhg−1, 0.2C) and coulombic efficiency (99.06%) after 160 cycles at 70 °C. Thus, FR-SPE1 is argued to provide an effective approach for more broadly enhancing lithium battery safety and performance.