6FAP-Derived Hydroxyl-Containing Polyimide Microsphere-Coated PE Separator for Lithium-Ion Batteries

<title>Abstract</title> <p> In this study, hydroxyl-containing polyimide (HPI) microspheres coated polyethylene (PE) separator was fabricated through the utilisation of an electrospraying technique. An investigation was conducted to systematically and comprehensively characterise HPI- and polyimide (PI)-coated separators with different microsphere loadings (8, 10, and 12 wt%). The findings of the study demonstrated that the incorporation of HPI microspheres led to a significant enhancement in the thermal stability and suppression of the thermal shrinkage of the PE separators. In addition, the HPI-coated separators exhibited superior electrolyte wettability and electrolyte uptake in comparison to both pristine PE and commercial Al ₂ O ₃ -coated separators. Among all samples, the HPI-8 separator demonstrated the lowest electrolyte contact angle and the highest lithium-ion transference number (0.58). Electrochemical analysis further demonstrated that the HPI-8 separator exhibited the highest discharge specific capacity at 1 C, while maintaining optimal Coulombic efficiency and cycling stability over 300 cycles. The findings of this study indicate that HPI microsphere coatings are an effective strategy for improving the safety and electrochemical performance of lithium-ion battery separators. </p>