Preparation Of Graphene/Carbon Nanotube Nanocomposite And Its Electrochemical Performance

Due to the decreasing amount of fossil energy storage around the world,the development and utilization of new energy is extremely urgent.At the same time,the research on supercapacitors has also received more and more attention.This thesis is devoted to the preparation of new supercapacitor electrode materials through simple methods.First,the reduced graphene oxide(rGO)/carbon nanotube(CNTs)composite hydrogel was prepared by a one-step hydrothermal method,and then combined with small organic molecule hydroquinone(HQ),transition metal oxide Li Mn₂O₄(LMO)and the conductive polymer polyaniline(PANI)is compounded to obtain a ternary nanomaterial.The specific content is divided into the following four parts:1.Using oxalic acid as a reducing agent,graphene oxide(GO)and reflux acidified CNTs are self-assembled to synthesize rGO/CNTs hydrogel by one-step hydrothermal method.The electrochemical test results show that when the current density is 0.5A·g^-1,the specific capacitance of rGO/CNTs reaches 142 F·g^-1.After 2000 cycles of charging and discharging at a current density of 5 A·g^-1,the specific capacitance of rGO/CNTs retained 99%.2.Using oxalic acid as the reducing agent,the rGO/CNTs/HQ hydrogel is directly synthesized by compounding HQ with GO and acidified CNTs by a one-step hydrothermal method.Compared with rGO/CNTs,the electrochemical performance of rGO/CNTs/HQ has been improved.The electrochemical test results show that at a current density of 0.5 A·g^-1,the specific capacitance of rGO/CNTs/HQ can reach 219F·g^-1.After 2000 cycles of charging and discharging at a current density of 5 A·g^-1,the specific capacitance of rGO/CNTs/HQ retained 94%.3.Using the prepared rGO/CNTs hydrogel as a matrix,the rGO/CNTs/LMO nanocomposite was synthesized by in-situ low-temperature hydrothermal oxidation-reduction reaction.Compared with pure LMO nanoparticles,rGO/CNTs/LMO performs better in terms of specific capacitance,cycle performance and rate capability.At a current density of 0.5 A·g^-1,the specific capacitance of rGO/CNTs/LMO can reach 396 F·g^-1,which is much higher than the 221 F·g^-1 of pure LMO.At a current density of 10 A·g^-1,the specific capacitance still has 309 F·g^-1.After 2000 cycles of charging and discharging at a current density of 5 A·g^-1,the specific capacitance of rGO/CNTs/LMO retained 93%.4.Using the prepared rGO/CNTs hydrogel as a matrix,under the action of the oxidant ammonium persulfate(APS),low-temperature chemical oxidation is used to polymerize the aniline monomer on the rGO/CNTs hydrogel in situ to form rGO/CNTs/PANI composite material.After electrochemical testing,when the current density is 0.5 A·g^-1,the specific capacitance of rGO/CNTs/PANI is 372 F·g^-1.After2000 cycles of charging and discharging at a current density of 5 A·g^-1,the specific capacitance of rGO/CNTs/PANI retained 70%.