Construction of PMIA@PAN/PVDF-HFP/TiO_(2) coaxial fibrous separator with enhanced mechanical strength and electrolyte affinity for lithium-ion batteries

Poly(m-phthaloyl-m-phenylenediamine)(PMIA)is promising as the separator in lithium-ion batteries(LIBs)for its excellent thermostability,insulation and self-extinguishing properties.However,its low mechanical strength and poor electrolyte affinity limit its application in LIBs.In this work,a new PMIA@polyacrylonitrile-polyvinylidene fluoride hexafluoropropylene-titanium dioxide(PMIA@PAN/PVDFHFP/TiO_(2))composite fibrous separator with a coaxial core-shell structure was developed by combining coaxial electrospinning,hot pressing,and heat treatment techniques.This separator not only inherits the exceptional thermostability of PMIA,showing no evident thermal shrinkage at 220 ℃,but also reveals improved mechanical strength(29.7 MPa)due to the formation of firm connections between fibers with the melted PVDF-HFP.Meanwhile,the massive polar groups in PVDF-HFP play a vital role in improving the electrolyte affinity,which renders the separator a high ionic conductivity of 1.36×10^(-3)s/cm.Therefore,the LIBs with PMIA@PAN/PVDF-HFP/TiO_(2)separators exhibited excellent cycling and rate performance at 25℃,and a high capacity retention rate(76.2%)at 80℃for 200 cycles at 1 C.Besides,the lithium metal symmetric battery assembled by the separator showed a small overpotential,indicating that the separator had a role in inhibiting lithium dendrites.In short,the PMIA@PAN/PVDF-HFP/TiO_(2) separator possesses a wide application prospect in the domain of LIBs.