ATMP Doped Conductive PANI/CNTs Composite Hydrogel Electrodes toward High Energy Density Flexible Supercapacitors

Although flexible supercapacitors (FSCs) have attractedtremendousattention, synthesis of supercapacitor electrodes that have outstandingelectrochemical performance and excellent flexibility remains a continuousdilemma. Herein, conductive polymer composite hydrogels were synthesized via in situ polymerization of aniline (ANI) in a mixtureof polyvinyl alcohol (PVA) and carbon nanotubes (CNTs), for whichamino trimethylene phosphonic acid (ATMP) was employed as an organicdoping acid. The as-prepared polyaniline (PANI)/PVA/ATMP/CNTs (PPAC)composite hydrogel electrodes exhibit a specific capacitance of upto 389.5 F g(-1) at 0.5 A g(-1), satisfactorylong-term cycling stability (83.87% capacitance retained after 10,000charge/discharge times), and outstanding flexibility (97% capacitanceretained over 200 repeated bends), and the incorporation of ATMP enhancedelectrochemical performances of PPAC composite hydrogel electrodes.Besides, the synergistic effects offered by high electrical conductivityof CNTs, pseudocapacitance of PANI, and the doping effect of ATMPmay further contribute to the excellent electrochemical behavior ofhydrogel electrodes. The result of the energy storage mechanism impliedthat the electrochemical process of the PPAC composite hydrogel electrodeinvolved both diffusion-controlled and surface capacitive processes.The all-hydrogel-state FSC based on the PPAC hydrogel electrode showsa favorable energy density of 12.8 W h kg(-1) at 125.0W kg(-1) as well as long-life stability of 77.31%capacitance retention after 10,000 charge/discharge cycles. This workis promising for the preparation of high-performance composite hydrogelelectrodes for wearable and flexible energy storage devices.