Electronically conductive MXene clay-polymer composite binders for electrochemical double-layer capacitor electrodes

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Electrochemical double-layer capacitors recently attract strong attention because of their fast and stable charge/discharge characteristics and their high-power density. To improve the performance of EDLCs, it is necessary to conduct comprehensive studies on electrode, including the binder. An ideal binder for an EDLC must have high adhesion ability to the electrode components and should be electronically conductive. Here, we synthesize a composite binder consisting of MXene clay and poly(acrylonitrile-co-butyl acrylate) using an in-situ emulsion polymerization. This is a first report of an in-situ polymerization method to make a conducting composite binder with good mechanical, adhesion, and electronic conducting properties. An EDLC containing electrodes of activated carbon and MXene clay/poly(acrylonitrile-co-butyl acrylate) composite binder shows a high specific power of 8510 W kg−1 with a high specific energy of 23.6 Wh kg−1. This is a significant improvement over EDLC electrodes containing only activated-carbon and poly(acrylonitrile-co-butyl acrylate). The excellent performance is attributable to the binder's high conductivity and toughness due to improved interactions among the electrode components.