Preparation Of Flexible Self-Healing Hydrogel Electrolyte And Its Application In Smart Supercapacitors

With the increasing variety of personalized electronic products,the demand for adaptive energy storage devices is also higher and higher.Flexible supercapacitors with both flexibility and safety are gradually coming into view,and electrolyte is an important step towards diversification of flexible supercapacitors.The traditional electrolyte may be damaged or separated from the electrode after the device is damaged,leading to failure or even serious safety problems.Therefore,inspired by the self-healing phenomenon of organisms,a flexible gel electrolyte capable of self-healing is designed and applied to supercapacitors,which can not only have good mechanical properties but also self-repair after damage,and meet the requirements of flexibility and stability.In this paper,hydrogel electrolytes with strong flexibility,adhesion,high conductivity and fast self-healing ability are prepared by strengthening the self-healing ability of gel through different cross-linking methods and applied to supercapacitors.The specific contents of the research are as follows:（1）Taking 3-aminophenylboric acid（PBA）as a monomer,the poly3-acrylamidophenylboronic acid（AAPBA）monomer was obtained by condensation reaction,and the AAPBA monomer and acrylamide（AM）monomer were further condensed to obtain the AAPBA polymer chain.P（AAPBA-co-AM）hydrogel electrolyte with high flexibility,strong adhesion and self-healing ability was prepared by copolymerization of AAPBA polymer linked with AM at 60°C.Its structure and morphology were characterized by FTIR and SEM,respectively.By exploring gel properties under different solvent contents,flexible hydrogels with high mechanical strength（strain>5000%）were obtained.The gel’s hydrogen-bonding rich structure also makes it adhesive.Based on the absorption ability of P（AAPBA-co-AM）hydrogel,the conductivity of the polymer gel was enhanced,and the specific capacitance of the device reached 116 F·g^-1and 35.1 m S·cm^-1at the current density of 1 A·g^-1,and retained 74%of the original capacitance after 2000 cycles.The structure and properties of the device remain almost unchanged in the face of different degrees of bending,folding,and multiple cuts/heals,showing good flexibility,self-healing,and electrochemical stability.（2）Poly3,4-dihydroxyaniline polymer chain（P4-AC）was synthesized by using 3,4-dihydroxyaniline（4-AC）as initiator,and its structure was correctly characterized by FTIR.The conductive gel P（AAPBA-co-P4-AC）was obtained by cross-linking the polymer chain of AAPBA with P4-AC at alkaline room temperature.The gel has good flexibility（fracture stress66.94 k Pa,fracture strain 1178.32%）and adhesive properties.After 10 incisions/repairs,the fracture stress of the gel was 82%and the strain recovered to 91%.At the current density of 1A·g^-1,the specific capacity of the capacitor is 93.85 F·g^-1,and the ionic conductivity reaches53.19 m S·cm^-1.After 2000 cycles,95%of the initial capacitance,with excellent cycling stability.In the face of different degrees of bending and folding,the device can still maintain good structure and electrochemical performance.The ionic conductivity and cyclic stability remained92%of the initial state after multiple incisions/healing.（3）A gel-integrated intelligent supercapacitor was prepared by using P（AAPBA-co-AM）gel doped with activated carbon（C）as flexible electrode and P（AAPBA-co-P4-AC）as flexible electrolyte.Not only can the device achieve overall stretching,but it can still achieve flexible deformation after fracture/healing.Its ionic conductivity is 20 m S·cm^-1and its capacity remains95%of the original capacitance after 2000 cycles.The electrochemical properties of the device remain unchanged after bending,folding and fracture/healing.