ABSTRACT Separator materials with excellent heat resistance and dimensional stability are critical to the performance of energy storage devices. Herein, benzimidazole‐containing polyimide (BPI) nanofiber membranes are developed as separators for supercapacitors (SCs). Firstly, 2‐(4‐Aminophenyl)‐5‐aminobenzimidazole (APBIA) is polymerized with three dianhydrides, including 4,4′‐(hexafluoroisopropyl)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 4,4′‐(4,4′‐isopropylidene diphenoxy)diphthalic anhydride (BPADA) to synthesize poly(amic acid) (PAA) solutions. PAA nanofiber membranes are then fabricated via electrospinning, followed by thermal imidization at 300°C to obtain BPI membranes, which are assembled into coin‐shaped SC cells as separators. Systematic investigations are conducted on the effects of dianhydride type, PAA concentration, imidization time, and heating rate on SC electrochemical performance. Results indicate that the BPI‐6FDA‐15‐120‐5 (PAA concentration: 15 wt%, imidization time at 300°C: 120 min, heating rate: 5°C min −1 ) membrane achieves optimal properties: 88.9% porosity, 396.1% electrolyte uptake, and 1.78 S m −1 ionic conductivity. The corresponding SC exhibits 105.6 F g −1 specific capacitance at 0.5 A g −1 , 60% capacitance retention at 10 A g −1 , and excellent stability over 45,000 charge–discharge cycles. Compared with commercial polypropylene and cellulose separators, the preferred BPI membranes demonstrate excellent mechanical, thermal, and electrochemical properties, confirming their potential for energy storage applications.
Wang et al. (2026) studied this question.