Preparation And Electrochemical Properties Of Polyaniline-based Electrode Materials And Iron-based Electrode Materials

Lithium-ion batteries（LIBs）have received extensive attention in recent years and are considered to be one of the most potential energy storage devices.Research on electrode materials that are easy to prepare,low-cost,environmentally friendly,and have excellent electrochemical performance is the current main goal.In this paper,a series of modification and modification are carried out according to the advantages and disadvantages of polyaniline and iron oxide electrode materials,and their electrochemical and battery performances are studied as electrode materials for lithium ion batteries.Mainly include:（1）Preparation of polydopamine/polyaniline（PDA-PANI）composites and their electrochemical properties as cathode materials for lithium-ion batteries;（2）Nanotubular iron oxide（Fe₂O₃）and graphene（RGO）Preparation of composite materials and study on their electrochemical properties as anode materials;（3）Preparation of three-dimensional graphene（RGO）and acidified carbon tubes（CNTs）-coated iron oxide（Fe₂O₃）nanoframe composites and their electrochemical properties as anode materials performance study.The specific content is as follows:Polydopamine/polyaniline（PDA-PANI）with fibrous morphology was prepared by oxidative polymerization using aniline and dopamine as monomers.Due to the good electrical conductivity of PANI fibers and the adhesion of PDA and its co-doping effect,the as-prepared PDA-PANI cathode material has good electrochemical performance.CV measurement showed that the slope values of PDA-PANI（5%）at different potentials were0.707,0.769 and the slope values of PDA-PANI（20%）at different potentials were 0.648,0.568,indicating the synergistic energy storage process,PDA-PANI（5%）shows a relatively large slope value,indicating that the PDA-PANI（5%）electrode has a higher energy contribution to the capacitive process than the PANI electrode,which indicates that doping an appropriate amount of dopamine in PANI is beneficial to increase the total energy of the capacitive process.store.The EIS results show that the charge transfer resistance of PDA-PANI（5%）is the smallest,which is much lower than that of pure polyaniline,indicating that the process at the electrode/electrolyte interface has a fast charge transfer rate.At the same time,at lower frequency,the Z_w value of PDA-PANI（5%）is smaller and the linear slope is larger,indicating that the diffusion rate in the composite electrode is faster and has typical capacitance characteristics,which is beneficial to the electrode material to improve the rate performance.Using nanotubular iron oxide（α-Fe₂O₃）and graphene oxide（RGO）as raw materials and polyvinylpyrrolidone（PVP）as surfactant,a series of graphene in different proportions were prepared by a simple hydrothermal method without further calcination/iron oxide（RGO@Fe₂O₃（1-1）,RGO@Fe₂O₃（1-2）,RGO@Fe₂O₃（1-5）,RGO@Fe₂O₃（1-10））composites.Its electrochemical performance and battery performance as anode materials for lithium-ion batteries were explored.Electrochemical and battery performance studies show that the composite electrode material RGO@Fe₂O₃（1-10）has the best rate performance and cycle stability.Among them,the capacity of RGO@Fe₂O₃（1-10）is 775.2 m Ah·g^-1 in the first cycle,and the specific capacity remains at 538.2 m Ah·g^-1 after 50 cycles,even at a high current density of 2000 m A·g^-1,The discharge specific capacity can still be maintained at 430.3m Ah·g^-1,which is much higher than that of pure Fe₂O₃ and other proportions of composite materials.Its excellent rate and cycling performance benefit from the enhanced electronic conductivity and the open pore structure of the composite,which facilitates the conduction and diffusion process of electrons and lithium ions inside the composite electrode.The research shows that the composite electrode material RGO@Fe₂O₃（1-10）has the best electrochemical performance..Graphene（RGO）,carbon nanotubes（CNTs）as conductive dispersion materials,graphene/carbon tubes/iron-based metal organic framework（MOF）composite precursors were prepared by in situ reaction,and graphene/carbon tubes were prepared by heat treatment/Fe₂O₃ composite material（RGO-CNT-K3-Fe₂O₃）,and used it as a negative electrode material for lithium-ion batteries for electrochemical performance testing.The research results show that the RGO-CNT-K3-Fe₂O₃ composite still has a high discharge specific capacity of1025.8 m Ah·g^-1 after 60 cycles at a current density of 100 m A·g^-1.Even at a high current density of 2000 m A·g^-1,the RGO-CNT-K3-Fe₂O₃ composite can stably provide a discharge capacity of about 486.8 m Ah·g^-1.When the current is reduced to 100 m A·g^-1,The discharge specific capacity can be recovered to a specific capacity of 783 m Ah·g^-1,which is similar to the initial capacity.Compared with K3-Fe₂O₃,the RGO-CNT-K3-Fe₂O₃ composite exhibits excellent cycling performance,capacity retention and rate capability.The high reversible lithium storage capacity of the composite RGO-CNT-K3-Fe₂O₃ is due to the superior flexible conductive network provided by r GO and CNT,which shortens the diffusion path of Li⁺and alleviates the volume change during repeated lithiation/delithiation.The in-situ generation of MOF improves the dispersibility of the material system and prevents the reduction of cycle stability caused by the aggregation of electrode materials during charging and discharging.