Design Of Polyaniline-polyvinyl Alcohol Conductive Hydrogel And Its Application In Flexible Supercapacitors

Flexible supercapacitors are regarded as promising flexible energy storage devices due to their electrochemical sustainability,certain mechanical flexibility,fast charging and discharging capability and long cycle life.As the key part of flexible capacitors,flexible electrodes are very important.In order to obtain flexible supercapacitors with high flexibility,lightweight and low cost,the traditional method of fabricating flexible electrodes is to coat or integrate electroactive materials on non-electroactive elastic matrix materials.However,these non-electroactive substrates have a detrimental effect on the overall electrochemical performance of the supercapacitor.And the effective contact between the electrode and the gel electrolyte is limited by the poor diffusion of the insulating polymer gel,resulting in large contact resistance.Therefore,the conventional flexible electrodes also hinder the electrochemical performance of the device.Conductive polymer hydrogel combines the electroactivity of conductive polymers and the unique properties of hydrogels?flexibility,stretchability,the larger surface area for electrochemical reactions,etc.?,making them an ideal framework for building flexible supercapacitors.This thesis mainly focuses on how to design and fabrication of flexible polyaniline-polyvinyl alcohol?PANI-PVA?hydrogel with good mechanical properties,electrochemical properties and self-healing properties,and its application in flexible all-solid supercapacitors.This thesis mainly includes the following aspects:?1?A flexible polyaniline hydrogel?Sucrose cross-linked polyaniline hydrogel,PH-S?with good electrochemical properties was prepared based on the hydrogen bonding between PVA and sucrose and the hydrogen bonding between sucrose and aniline?AN?,which allowed PANI to polymerize along the PVA network.The fracture stress of the PH-S hydrogel is 131.1 KPa,the modulus is 180.6 KPa,and the elongation at break is 129.0%.The PH-S hydrogel has excellent electrochemical performance,the area specific capacitance of PH-S electrode can reach 1698.4m F/cm²?at 1 m A/cm²?.The all-solid flexible supercapacitor based on PH-S provides a large area specific capacitance of 464.7 m F/cm²?at 1 m A/cm²?.When the current density increases 10 times,the capacitance retention rate is 98.7%.Its capacitance retention rate is 82.4%after 2000 charge-discharge cycles.?2?To further improve the mechanical properties of polyaniline hydrogels,a double network polyaniline hydrogel?Aminobenzene borate cross-linked polyaniline hydrogel,PH-A?with excellent mechanical and electrochemical properties was prepared at low temperature by combining rigid PANI molecular chains with flexible PVA polymer chains by dynamic borate bonding.The PH-A hydrogel has excellent mechanical properties with a breaking elongation of 601.8%,a fracture stress of 242KPa and a Yang's modulus of 235.1 KPa.PH-A hydrogel has good electrochemical performance,and its area specific capacitance can reach 1076.9 m F/cm²?at 1m A/cm²?.The all-solid flexible supercapacitor based on PH-S provides a good area specific capacitance of 243.6 m F/cm²?at 0.5 m A/cm²?.When the current density increases 10 times,the capacitance retention rate is 95.5%.Its capacitance retention rate is 86.4%after 1000 charge-discharge cycles.?3?The flexible energy storage devices unavoidably suffer physical damage during used.Therefore,in this thesis we used the reversible hydrogen bond between phytic acid?PA?and PVA and glycerol and PVA,respectively,to impart self-healing properties to the hydrogels,while also used carbon nanotubes?CNT?to provide high electrical conductivity,PANI to provide pseudo-capacitors,to prepare polyaniline-carbon nanotube-polyvinyl alcohol?PANI-CNT-PVA?ternary hydrogels with high conductivity,excellent mechanical properties and good electrochemical properties.The electrical conductivity of PANI-CNT-PVA hydrogel is 0.3?s/cm,which has good conductivity.PANI-CNT-PVA hydrogel can be reshaped by heating and cooling.The PANI-CNT-PVA hydrogel has mechanical properties,for its elongation at break reaches 722%,the fracture stress is 449 KPa,Young's modulus is53.6 KPa,toughness is 1.6 MJ/m³.The PANI-CNT-PVA after self-healing displayed elongation at break of 483%,a fracture stress of 236 KPa,a Yang's modulus of 39.5KPa,and a toughness of 0.7 MJ m^–3.The all-solid flexible supercapacitor based on PANI-CNT-PVA has good electrochemical performance and excellent self-healing performance.The area specific capacitance of PANI-CNT-PVA based supercapacitor is 260.1 m F/cm²?at 0.5 m A/cm²?.After 1000 charge-discharge cycles,its capacitance retention rate is 97.5%.After 10 times of cutting/self-healing process,the capacitance retention rate is 95.4%.