Crystalline Al2O3 modified porous poly(aryl ether ketone) (PAEK) composite separators for high performance lithium-ion batteries via an electrospinning technique

Abstract

The thermostability and wettability of a separator play key roles in improving the safety and electrochemical properties of lithium-ion batteries (LIBs). Given this fact, a crystalline aluminium oxide (Al₂O₃) nanoparticle coated poly(aryl ether ketone) (PAEK) composite membrane with excellent comprehensive properties was fabricated by an electrospinning technique, and further used as a porous separator for high-performance lithium-ion batteries (LIBs). The structure, thermal stability, morphology, liquid electrolyte uptake, porosity, contact angle, ionic conductivity and electrochemical performance of the PAEK–Al₂O₃ blend separator were investigated. Notably, the PAEK–Al₂O₃ separator showed much stronger anti-shrinkage properties (no dimensional changes) than a commercial polypropylene (PP) separator (severe thermal shrinkage) at 150 °C over 1 h. In addition, compared with those of PAEK and commercial PP separators, the degradation temperatures of the PAEK–Al₂O₃ separator were higher, with values over 500 °C. The PAEK–Al₂O₃ separator also had superior electrolyte wettability, and its electrolyte uptake reached 561%. The porosity and ionic conductivity of the composite separator were 89.4% and 3.15 mS cm⁻¹, respectively. As a result of the abovementioned outstanding properties of the blend separator, the cell assembled from the PAEK–Al₂O₃ separator exhibited a high discharge capacity of 158.2 mA h g⁻¹ (LiFePO₄/Li⁺) during 100 cycles and a superior C rate performance. Hence, the obtained PAEK–Al₂O₃ separator enhanced the safety and electrochemical properties of the corresponding LIB.