Design And Development Of Flexible Electrodes Based On Electrically Conductive Hydrogels And Their Performance Investigation

In order to power wearable electronic devices,various flexible energy storage devices have been developed with desired mechanical and electrical properties.Flexible supercapacitors have become one of the most investigated flexible energy storage devices due to their high-power density,fast charge and discharge speed,and good cycle stability.The design and development of flexible electrode materials is a key towards flexible supercapacitors.The three-dimensional network of electrically conductive hydrogels（ECHs）can not only store a large amount of electrolyte,but also provide a stable pathway for electron and ion transfer during the electrochemical reaction process.It is an ideal framework for the design and construction of flexible supercapacitor electrodes.However,the mechanical performance and electrochemical performance of the traditional ECH electrodes are far from the level of conventional rigid devices,which severely limits their practical applications.This work focuses on the design principles of ECH-based flexible electrodes with excellent mechanical and electrochemical properties.The research work mainly includes the following contents:（1）The double-network LaMnO₃ hydrogel electrodes（LaMnO₃-PAM/PVA）were prepared via photopolymerization and freeze-thaw cycle method.The hydrogel matrixs with a double network structure have increased mechanical properties.The LaMnO₃ particles with a porous morphology can not only provide electrochemical properties,but also serve as a reinforcing material to further improve the mechanical strength of the hydrogels.The LaMnO₃-PAM/PVA hydrogel electrodes have a tensile strength of 1.81 MPa and an elongation at break of 450%.The specific capacitance is 392 F g^-1 at 1 Ag^-1,the capacity retention rate remains 90%after 10,000 charge-discharge cycles,and the coulombic efficiency is close to 100%.（2）The ternary multi-dimensional structure hydrogel electrodes（MXene/PPy-PVA）were prepared by freeze-thaw cycle method and in-situ oxidation.The interconnected one-dimensional polypyrrole（1D PPy）fibers were used as"bridges"to connect the two-dimensional MXene（2D MXene）sheet to the three-dimensional polyvinyl alcohol（3D PVA）hydrogel matrix,obtaining excellent electrochemical performance and mechanical properties.The maximum tensile strength of the MXene/PPy-PVA hydrogel electrode is 10.3 Mpa and the elongation at break is 380%,and the specific capacitance is 614 F g^-1 at 1 Ag^-1.In addition,at a current density of 10 Ag^-1,the capacitance remains 100%after 10,000 cycles of charge and discharge,and the coulomb efficiency is 99.6%.（3）Polyaniline-polyvinyl alcohol/agarose（PANI-PVA/Agarose）self-healing hydrogel electrodes were prepared via one-step macromolecular self-assembly,where 3-aminobenzene borate hydrochloride（ABA）and aniline monomer（ANI）were copolymerized,and the dynamic borate bonds caused the gelation of polyvinyl alcohol（PVA）.The hydroxyl groups on agarose and PVA chains can form a reversible hydrogen bonding.Under the synergistic effect of dynamic boronic ester bonds and hydrogen bonding,PANI-PVA/Agarose hydrogels can complete self-healing process within 15minutes after being physically damaged.The tensile strength of the self-healed PANI-PVA/Agarose hydrogel is 200 kPa,which can reach 92.2%of its original state.At a current density of 1 mA cm^-2,the specific capacitance is 1920.6 mF cm^-2,which reached 95.3%before self-healing.