Polymer-based Flexible Membrane Electrode And Integrated Flexible Supercapacitor

With the rapid development of portable electronic products,the research of flexible energy storage devices has also attracted much attention.The development of a high-flexibility and high-electrochemical performance energy storage device is of great significance for further promoting the flexible electronics market.Among many flexible energy storage devices,flexible supercapacitors are favored by researchers for their fast charging and discharging capability,long cycle life,and high power density.Choosing a suitable method to fabricate high performance flexible electrode is critical to the electrochemical performance of the entire device.In this paper,the selection of flexible substrate,the growth method of electrochemical active materials,the improvement of immersion precipitation phase transformation method and the optimization of the structure of traditional sandwich flexible device are studied.The main contents are as follows:(i)Polyaniline-polyethersulfone flexible membrane electrode is prepared by solvent induction method.Polyethersulfone and aniline monomers are prepared as casting solution,and the in-situ polymerization of monomers occurred in a coagulation bath containing doped acids and oxidants.In this way,a |rigid-flexible"polymer me mbrane electrode is constructed by inter molecular hydrogen bonding force formed involving polyaniline and polyethersulfone.The effects of coagulation bath conditions(doped acid concentration and oxidant content)on membrane structure,electrical conductivity,and electrochemical performance are investigated.The asymmetric device assembled by optimized membrane electrode and activated carbon flexible membrane electrodes achieves a maximum energy density of 813 mWh·m-2.(ii)In order to improve the pore structure of the membrane obtained by solvent-induced method,polyethersulfone and nickel hydroxide firstly prepared as casting solution and the immersion precipitation phase transformation method is modified to slow down the diffusion rate between two phases.In other words,the initial ecological membrane undergoes a slow microphase separation process of solvent phase and vapor phase by water vapor induced slow phase separation.The morphology of membrane electrodes can be symmetrical by this slow phase inversion technology,while the morphology of membrane electrodes obtained by traditional phase inversion method presents an asymmetrical structure consisting of finger-like,macroporous and multi-microporous.This symmetrical structure is more conducive to the rapid transport of electrolyte ions,thus improving the electrochemical performance of membrane electrodes.The results show that the structure and electrochemical performance of the membrane electrodes are optimal when the relative humidity of water vapor phase is 70%,phase transformation time is 10 min,and phase transformation temperature is 40 ℃.The device assembled by the optimized membrane electrode and the activated carbon flexible membrane electrode achieves a maximum energy density of 30.01 Wh.kg-1.(iii)The presence of hydrophobic polymers in polymer-based membrane electrodes affect the wettability of the electrodes in the previous two chapters,therefore,carboxylated chitosan hydrogel with excellent wettability and electrophilic it y is used as the flexible substrate of the electrode.The electrochemically active substances are wrapped in the flexible matrix by in-situ polymerization of aniline monomer,and the conductivity of the flexible electrode is further enhanced by gold nano particles.Finally,a flexible electrode with integrated collector/electrode material is fabricated by using carbon cloth as collector,and the structure of traditional sandwich device is optimized to alleviate the interface problem so as to obtain a flexible supercapacitor with integrated electrode/electrolyte.The results show that gold doping can effectively improve the electrochemical performance of membrane electrodes,and the device structure of integrated electrode/electro 1 ytes is conducive to the effective transmission of electrolyte ions.