A polyacrylonitrile (PAN)-interpenetrating cross-linked polyoxyethylene (PEO) network (named XANE) was synthesized acting as separator and as gel polymer electrolytes simultaneously. SEM images show that the surface of the XANE membrane is nonporous, comparing to the surface of the commercial separator to be porous. This property results in excellent electrolyte uptake amount (425 wt %), and electrolyte retention for XANE membrane, significantly higher than that of commercial separator (200 wt %). The DSC result indicates that the PEO crystallinity is deteriorated by the cross-linked process and was further degraded by the interpenetration of the PAN. The XANE membrane shows significantly higher ionic conductivity (1.06-8.21 mS cm(-1)) than that of the commercial Celgard M824 separator (0.45-0.90 mS cm(-1)) ascribed to the high electrolyte retention ability of XANE (from TGA), the deteriorated PEO crystallinity (from DSC) and the good compatibility between XANE and electrode (from measuring the interfacial-resistance). For battery application, under all charge/discharge rates (from 0.1 to 3 C), the specific half-cell capacities of the cell composed of the XANE membrane are all higher than those of the aforementioned commercial separator. More specifically, the cell composed of the XANE membrane has excellent cycling stability, that is, the half-cell composed of the XANE membrane still exhibited more than 97% columbic efficiency after 100 cycles at 1 C. The above-mentioned advantageous properties and performances of the XANE membrane allow it to act as both an ionic conductor as well as a separator, so as to work as separator-free gel polymer electrolytes.
The synthesis of a gelled polymer electrolyte (GPE) using poly(ethylene glycol) blending poly(acrylonitrile) (i.e., PAN‐b‐PEG‐b‐PAN) as a host, dimethyl formamide (DMF) as a plasticizer and LiClO4 as an electrolytic salt for electric double layer capacitors (EDLCs) is reported. The PAN‐b‐PEG‐b‐PAN copolymer in the GPE has a linear configuration for high ionic conductivity and excellent compatibility with carbon electrodes. When assembling the GPE in a carbon‐based symmetric EDLC, the copolymer network facilitates ion motion by reducing the equivalent series resistance and Warburg resistance of the capacitor. This symmetric cell has a capacitance value of 101 F g−1 at 0.125 A g−1 and can deliver an energy level of 11.5 Wh kg−1 at a high power of 10 000 W kg−1 over a voltage window of 2.1 V. This cell shows superior stability, with little decay of specific capacitance after 30 000 galvanostatic charge‐discharge cycles. The distinctive merit of the GPE film is its adjustable mechanical integrity, which makes the roll‐to‐roll assembly of GPE‐based EDLCs readily scalable to industrial levels.
This study examines the linear triblock copolymer design of poly(acrylonitrile)-b-poly(ethylene glycol)-b-poly(acrylonitrile) (PAN-b-PEG-b-PAN) for a gel polymer electrolyte (GPE) swollen with dimethylformamide dissolving LiClO 4 . The study demonstrates the synergistic effect of the nitrile and ether functionalities in facilitating ion transport in the carbon films of electric double-layer capacitors (EDLCs). A GPE with a tuned AN/EG ratio exhibits ionic conductivity at approximately 10 −2 S cm −1 . The linear configuration incorporates the GPE border into the carbon electrodes. The PAN chain promotes ion solvation and transport into the carbon interior, and the PEG chain coordinates the solvent molecules to form ion motion channels. The synergistic effect of the PAN and PEG blocks enables a GPE EDLC delivering more energy and power than EDLCs with a liquidphase electrolyte. The GPE EDLC delivers 20 Wh kg −1 (approximately 10 Wh L −1 ) at a high power of 10 kW kg −1 (approximately 5 kW L −1 ) when using a high-porosity carbon electrode derived from mesophase pitch activation.
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