Vapor-induced phase inversion of poly (m-phenylene isophthalamide) modified polyethylene separator for high-performance lithium-ion batteries

Abstract A separator plays a vital role in the performance and safety of lithium-ion batteries. The modification of the commercial polyolefin separators is the most practical way to overcome the low thermal stability and electrolyte wettability problems. Herein, we propose a simple vapor-induced phase inversion method to fabricate poly (m-phenylene isophthalamide) (PMIA) modified polyethylene (PE) separator (referred to PE@PMIA). During the phase inversion process, the porous PMIA layers are formed on both sides of the PE separator and the thickness of the whole modified separator is only 13 μm. Due to the introduction of the PMIA protective layers with high heat-resistant, the obtained PE@PMIA displays enhanced thermal stability, showing no dimension shrinkage after heat treatment at 150 °C for 30 min. The PE@PMIA separator also exhibits excellent electrolyte affinity, enhanced mechanical property, and excellent lithium dendrite resistance for batteries' superior safety. The assembled LiFePO4/Li cells using PE@PMIA separators show great cycling performances and good rate capability. These results demonstrated that the PE@PMIA separators are promising for high-performance lithium-ion batteries and the vapor induced phase inversion method could be extended to fabricate other modified separators.