Research On Energy Storage Electrode Material Modulation And Its Application In Devices

In recent years,with the rapid development of the wearable devices and the continuous expansion of its market scale,the demand for high-energy-density flexible energy storage devices has also increased.CNT/PANI-based flexible solid-state supercapacitors have the advantages of high power density,long cycle life,good flexibility and high safety,making them ideal energy storage devices for wearable electronic products.Electrode materials are the most important to the electrochemical performance of supercapacitors.Regarding the CNT/PANI-based supercapacitor,this thesis is mainly from the perspective of electrode material modification,and the CNT film substrate is treated in different ways to change its surface wettability,thereby realizing effective modulation of the physical and chemical properties of the PANI deposited on CNT film,and obtaining energy storage devices with excellent performance.The specific research contents are as follows:Firstly,the CNT film is annealed and evaporated gold to modulate its surface wettability,and cyclic voltammetry is used to prepare PANI electrode with pseudo-capacitance or electric double layer capacitance on this basis.The CNT film annealed in Ar atmosphere(CNT(Ar))is hydrophobic,while the CNT film thermally evaporated Au on both sides after annealing in Ar atmosphere(CNT(Ar)/Au)is hydrophilic.Therefore,PANI has different growth kinetics,microscopic morphology and chemical composition on the surface of the two CNT films.In addition,through X-ray photoelectron spectroscopy analysis,PANI grown on CNT(Ar)and CNT(Ar)/Au films has the same chemical bond morphology and different composition content:the former has an imine/amine nitrogen(-N=/-NH-)component ratio of 0.84,at this time PANI is closer to the state of semi-oxidized emerald,and has the best redox reaction capacity;the latter has a ratio of 2.33,corresponding to the fully oxidized state of PANI with weak redox reaction ability,so the device made by the former has typical pseudo-capacitance behavior,while the latter exhibits electric double layer capacitance behavior.Moreover,the influence of contact angle of CNT film on the PANI pseudocapacitance characteristics was further explored.The CNT film annealed in H₂ atmosphere is also hydrophobic,but the contact angle is significantly smaller than that of CNT(Ar)film.The-N=/-NH-ratio of the PANI deposited on its surface is also smaller than that of CNT(Ar)film,so the degree of oxidation-reduction reaction of the manufactured device is not as good as that of the device made of CNT(Ar)film.Through the above-mentioned facile processing methods,the microscopic morphology and chemical composition of PANI can be effectively controlled and devices with excellent performance can be obtained.Furthermore,the devices prepared with CNT(Ar)/Au film as substrate exhibit high area specific capacitance(539.17 m F cm^-2),long cycle life(92.04%capacity retention rate after 5000 cycles)and excellent flexibility,which can be comparable with the current best CNT/PANI-based supercapacitors.Secondly,by acidizing the CNT film to change its surface wettability and microstructure,the microscopic morphology and thickness of the PANI electrode can be effectively controlled,and the electrochemical performance of the supercapacitors can be significantly improved.After the original CNT film is fully immersed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid(volume ratio is 3:1),the pores between the CNT bundles are larger,the crisscross network structure is more orderly,and the surface of the film is more hydrophilic.In addition,the PANI electrode prepared is very loose and porous,which is beneficial to release the stress caused by the volume change of PANI during the reaction.And its effective contact area with the electrolyte is significantly increased,the ion transmission distance is also significantly reduced.Besides,the deposition rate of PANI increased to 4.60times the original and the mass of active material per unit area is significantly improved.Furthermore,the device assembled from acidified CNT film electroplated with PANI exhibits excellent electrochemical performance with high area specific capacitance of 991.25 m F cm^-2at current density of 0.25 m A cm^-2,long cycle life(94.16%capacity retention rate after 6000cycles)and excellent flexibility.