Synthesis Of A Novel Supramolecular Hydrogel Electrolyte With High Ionic Conductivity And Its Application In Supercapacitors

The development of flexible and wearable electronic devices brings new challenges to their energy devices.Supercapacitor is a new type of energy storage device which has the advantages of high power density of double-layer capacitor and high energy density of battery.However,conventional supercapacitors are susceptible to various mechanical deformations,causing security issues such as liquid leakage,chemical corrosion,etc.,which may cause irreversible damage to the function of the device and make it difficult to apply to flexible wearable electronic devices.First,the built-in energy device should be lightweight and liquid-free for acceptable portability.Second,these power devices are expected to have high stretchability,arbitrary deformability,and even self-healing ability to withstand repeated deformation or sudden fracture during long-term operation.In this context,stretchable and self-healable supercapacitors（SCs）using solid polymer hydrogel electrolytes are ideal power devices.However,several bottlenecks remain in the development of hydrogel-based flexible solid state supercapacitors.First,the high interfacial impedance between the electrode and the hydrogel electrode results in a large electron transport and diffusion resistance from the electrolyte to the electrode.Second,conventional polymer electrolytes lack inherent stretchability or self-healing ability,and are affected by various mechanical deformations,leading to safety issues such as liquid leakage and chemical corrosion.In this thesis,supramolecular hydrogel electrolyte materials with multiple dynamic valence interactions were synthesized by radical polymerization.and the performance of quasi-solid flexible supercapacitors constructed by using the gel was systematically studied.At the same time,its ionic conductivity,mechanical properties,optical transparency and self-healing properties were investigated.details as follows:Multi-functional TA-PAA-Fe³⁺/KCl supramolecular hydrogel（TPFGPE）was successfully prepared by using polyacrylic acid as polymer chain,Fe³⁺as crosslinking agent,tannic acid（TA）wrapped in the chain,and KCl as transport ion.The morphology of the gel was characterized by SEM,and its mechanical properties and adhesion were tested.And it is used in the construction of flexible solid supercapacitor,as follows:1.Acrylic acid monomers were polymerized into polyacrylic acid gels under the initiation of initiator ammonium persulfate by free radical polymerization method,in which we added Fe³⁺and polyphenol small molecule tannic acid to the acrylic acid solution,and KCl was used as the transport ion,the prepared gel has a pore structure ranging from 500 nm to 2μm,which is favorable for the transport of conductive ions in the gel,thus achieving high ionic conductivity(24.82 m S cm^-1).And the mechanical properties,self-healing and adhesion of the gel were studied,indicating the potential application of the gel electrolyte in energy devices of wearable electronic devices.The hydrogel with a width of 0.5 cm was stretched to 20 cm,and the gel was stretched to40 times its original length without breaking,demonstrating excellent stretchability.The gel is cut,and it can quickly self-heal into a complete gel after 3 minutes,and the small light bulb can be lit by a series-connected regulated power supply.At the same time,the adhesion of the gel was also evaluated and found to be able to hold up to 900g of weight.These properties make the solid-state flexible supercapacitor composed of the gel not subject to safety problems such as liquid leakage and chemical corrosion when affected by various mechanical deformations.It is an ideal electrochemical energy storage material in flexible electronic devices.2.In this chapter,the electrochemical capacitance performance of the electric double layer of the TA-PAA-Fe³⁺/KCl gel as electrolyte for solid-state flexible supercapacitors was investigated in depth.In addition,PVA/H₂SO₄ and PVA/KCl were fabricated for comparative experiments.Carbon-based materials,ZIF-67 series materials were used as electrode materials,and carbon cloth was used as conductive substrate to prepare electrodes.Activated carbon@carbon cloth,ZIF-67 bulk crystal@carbon cloth（Bulk-ZIF-67@CC）and multiporous carbon cloth ZIF-67@carbon cloth（MP-ZIF-67@CC）electrode were prepared.The SCs built with activated carbon as the electrode material has a capacitance of 66.8 m F cm^-2 at a current density of 1 m A cm^-2,which is higher than that of PVA/H₂SO₄(15.92 m F cm^-2)and PVA/KCl(9.28 m F cm^-2).The SCs constructed with the gel and Bulk-ZIF-67@CC at a current density of 0.5 m A cm^-2 has a capacitance of 10.29 m F cm^-2,energy density up to 1.425 m Wh cm^-2,and the density can reach 0.497 W cm^-2,the galvanostatic charge-discharge cycle was performed at a current density of 2 m A cm^-2,and the specific capacitance remained at 93.56%of the initial value after 5000 charge-discharge cycles.These results show that the application of TPFGPE on SCs has great advantages,with high specific energy as well as energy density and power density.3.In this chapter,a layer of polyaniline（PANI）was grown on the ZIF-67 series electrode materials by electrodeposition to prepare ZIF-67 nanosheets/PANI@CC（NSs-ZIF-67/PANI@CC）,ZIF-67 bulk crystal/PANI@carbon cloth（Bulk-ZIF-67/PANI@CC）and multiporous ZIF-67 crystal/PANI@carbon cloth（MP-ZIF-67/PANI@CC）electrodes.The SCs constructed by TPFGPE and NSs-ZIF-67/PANI@CC at a current density of 10 m A cm^-2 exhibits a capacitance of 2123 m F cm^-2,an energy density of 288.33 m Wh cm^-2,and a power density of 5.01 W cm^-2.Compared with PVA/H₂SO₄(1337 m F cm^-2)and PVA/KCl(1910 m F cm^-2)gels with SCs constructed with NSs-ZIF-67/PANI@CC,it has better electrochemical performance,and connectting three SCs in series as a power supply device,an LED bulb with a power of 5 W was successfully lit.And the SCs constructed by Bulk-ZIF-67/PANI@CC electrode and TPFGPE have a specific capacitance of 1584 m F cm^-2 at a current density of 10 m A cm^-2.The SCs constructed with MP-ZIF-67/PANI@CC electrode achieved a specific capacitance of 2106 m F cm^-2 at the same current density.In this chapter,we mainly construct SCs with different electrode materials,showing their high compatibility,and also demonstrate the application of the gel in energy storage devices.