High-safety Poly(ethylene-Co-vinyl Acetate)/poly(ether Ether Ketone)/poly(ethylene-Co-vinyl Acetate) Composite Separator with the Thermal Shutdown Feature for Lithium-Ion Battery

The thermal safety of lithium-ion batteries (LIBs) is a major obstacle to expanding LIBs applications. High-safety separators with a thermal shutdown feature are considered the most promising and appealing thermal protection strategy for LIBs to avoid thermal runaway. Herein, a high-safety poly (ethylene-co-vinyl acetate)/poly (ether ether ketone)/poly (ethylene-co-vinyl acetate) (EVA/PEEK/EVA) composite separator is fabricated by dip -coating and thermally induced phase separation. Once the operating temperature exceeds 80 degrees C inadvertently (the thermal runaway onset temperature), the EVA layers of the EVA/PEEK/EVA separator are converted into barrier membranes to cut off ion transport and prevent battery reactions. Meanwhile, the PEEK substrate remains dimensionally stable even at temperatures up to 240 degrees C to avoid the dangers associated with thermal inertia after shutdown. Moreover, compared to the polyolefin separator (commercially available), the EVA/PEEK/EVA separator shows an increase of 42% and 77.1% in ionic conductivity and discharge capacity at the rate of 4C, respectively. Therefore, the EVA/PEEK/EVA separator can secure the LIBs without sacrificing electrochemical performance, and further expand the application of LIBs.