A high thermal stable pre‐oxidized polyacrylonitrile nanofiber separator for lithium‐ion battery

Abstract The separator as a main part of lithium‐ion batteries (LIBs) acts as a primary factor that affects the safety property of the battery. The pre‐oxidized PAN (OPAN) separator as an alternative separator with high temperature resistance was developed through the electrospinning of PAN by thermal stabilization. The prepared OPAN separator showed an exceptional dimensional thermal stabilization, without obvious dimensional shrinkage after treated in the oven at 300°C for 30 min, which improves the safety of LIBs at high temperatures. The OPAN separator had a high porosity and excellent affinity to the electrolyte, along with 351.3% of electrolyte uptake. Furthermore, the ionic conductivity and the interfacial resistance of OPAN separator were 1.63 mS/cm and 881 Ω, better than 0.65 mS/cm and 1463 Ω of commercial Celgard 2400 separator. In addition, the LiFePO 4 /Li battery assembled with OPAN separator given an outstanding initial discharge specific capacity and coulomb efficiency of 152.1 mAh/g and 97.9% and shown an excellent capacity retention ability of 92.3% after 100 cycles. The battery assembled with OPAN separator exhibits more excellent rate performance than PAN and Celgard 2400 separators at a charge current density of 0.2–3.0 C. It is believed that this excellent separator with such remarkable performances and low cost can be a promising separator candidate for safe LIBs.