Electrospun Poly(ether ether ketone) Nanofibrous Separator with Superior Performance for Lithium-Ion Batteries

Abstract

The thermal stability of a separator is extremely important for the safety of lithium-ion batteries (LIBs). Poly(ether ether ketone) (PEEK) is a potential material for use as a separator due to its good heat resistance and chemical stability. However, PEEK has inferior solubility, and is not easy to be prepared a porous separator. Herein, we report a novel soluble PEEK derivative containing polar and bulk groups and a series of porous separators prepared via an electrospinning technique. The synthesis of the PEEK was confirmed by Fourier transform infrared spectroscopy (FTIR), and the morphology of the membrane was examined by scanning electron microscopy (SEM). Several important properties, such as the thermal stability, liquid electrolyte uptake, contact angle, and lithium-ion conductivity, were measured. These electrospun PEEK separators including PEEK-5, PEEK-8 and PEEK-10 exhibited better thermal stability and wettability than a commercial polypropylene (PP) separator. Notably, the PEEK-8 separator exhibited the largest liquid electrolyte uptake of 524% and the highest ionic conductivity of 3.81 mS cm−1. More notably, the electrospun PEEK separators did not exhibit shrinkage at 150°C, and a coin cell assembled with the electrospun PEEK-8 separator possessed a discharge capacity of 118.9 mAh g−1 (LiFePO4/Li+) after 200 cycles at an elevated temperature of 60°C. Thus, the obtained electrospun PEEK separators can effectively enhance the safety and electrochemical performance of LIBs.