Tri-layer nonwoven membrane with shutdown property and high robustness as a high-safety lithium ion battery separator

This paper presents a tri-layer membrane featured with double amido functionalized poly(ether ether ketone) outer layers and a poly(methyl methacrylate) interlayer and its application as a lithium ion battery separator. On one hand, the outer layers possess outstanding stability and endurance, which helps the tri-layer membrane to resist harsh conditions. On the other hand, the fusible interlayer can melt to block the pores of membrane once temperature is higher than 100 °C, which helps to prevent the lithium ion transmission between electrodes to terminate reactions in LIB. As a result, the tri-layer membrane exhibits remarkable features, including high maximum service temperature (350 °C), no area shrinkage at 150 °C, and wide shutdown temperature window (100–270 °C). The high stability and the shutdown property can avoid the thermal runaway of lithium ion battery, and greatly improve the safety. In addition, the wettability of the membrane is dramatically increased (contact angle= 0 ° vs. electrolyte) due to the strong interaction between polar polymer matrix and polar electrolyte, and the ionic conductivity of tri-layer membrane is 25.8% higher than the Celgard-2325 membrane at 30 °C (the 25 µm PP/PE/PP tri-layer membrane). The discharge capacity of LIB-NW-CA/P/CA is 3.7%, 7.6%, 9.7%, 12.2%, 13.5% and 54.3% higher than that of LIB-Celgard at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C and 5 C, respectively.