Novel lithium ion battery separator based on hydroxymethyl functionalized poly(ether ether ketone)

Hydroxymethyl functionalized poly(ether ether ketone) (OHPEEK) was exploited as the separator of lithium ion battery (LIB). The stable OHPEEK backbone endows the membrane with high anti-shrinkage property (0% until 160 °C and only 18.3% at 240 °C) and high thermal stability (degradation temperature up to 282 °C). Due to the abundant polar groups of the OHPEEK, the wettability of OHPEEK membrane is improved, reflected by that the contact angle reduces to 24.6 °C, and the electrolyte uptake rises to 204% at 30 °C. The OHPEEK membrane shows a higher conductivity in the electrolyte (1 M LiPF6/EC/DME) compared with the Celgard 2400 PP separator. As a result, the LIB with the OHPEEK membrane possesses 0.3%–36.8% higher discharge capacity at the C-rate from 0.1 to 4 C and satisfactory cycling performance.