Application Research Of Conductive Polymer In Electrode Materials

With the development of human society,the demand for energy is also increasing.Since lithium-ion batteries have a series of advantages such as high operating voltage and energy density,low self-discharge rate and long cycle life,they have been widely studied in various fields,but this has also led to further shortages of lithium resources.As a result,more and more new energy storage systems have attracted widespread attention and research.Including sodium ion batteries,potassium ion batteries,magnesium ion batteries,aluminum ion batteries,etc.For sodium ion batteries or aluminum ion batteries with a large ionic radius,inorganic materials are not conducive to the insertion and removal of large cations.Organic electrode materials are mostly flexible structures,which have less restrictions on the radius of embedded ions.In principle,they are more suitable for storage of larger cations.In addition,organic materials have the advantages of low prices and environmental protection.They are ideal for new electrochemical energy storage systems.Polythiophene derivatives have the advantages of higher electrical conductivity,solubility,excellent electrochemical performance,good environmental stability,and ease of preparation.They are one of the most promising conductive polymers.However,limited by the degree of doping,the theoretical specific capacity is low.Secondly,such polymers are easily soluble in the electrolyte,resulting in short battery cycle life.The molecular structure of organic materials can be designed and composite materials can be improved.Therefore,in this dissertation,the organic electrode materials poly 3,4-dimethylthiophene(P3,4-Th)and polythiophene-coated Fe OCl composite electrodes were synthesized by chemical oxidation-reduction methods,and applied to lithium and sodium,respectively.And aluminum ion batteries,and the electrochemical performance and related reaction mechanism were investigated.The specific research content is as follows:1.The conductive polymer poly3,4-dimethylthiophene(P3,4-Th)was synthesized by chemical oxidation-reduction method,and its electrochemical performance and reaction mechanism in lithium/sodium ion batteries were explored.Studies have shown that when poly 3,4-dimethylthiophene(P3,4-Th)is used as the anode material of lithium ion batteries,the lithium storage capacity is 955.2 m A h g^-1,the cycle is stable for 450 times,and it has good rate performance.In the first fifty cycles,when the current density is increased to 2 A g^-1,the discharge specific capacity is still 100 m A h g^-1.When used in sodium ion batteries,the reversible capacity is 392.4 m A h g^-1.Since the ether electrolyte can form a more uniform and dense SEI film on the surface of the negative electrode,reducing electrochemical polarization,P3,4-Th shows a higher capacity in the ether electrolyte than the ester electrolyte with more stable cycling performance.2.In the field of aluminum ion batteries,we have studied the electrochemical performance and mechanism of P3,4-Th as an electrode material.P3,4-Th has a more ordered structure and better electronic conductivity than PTh,and P3,4-Th has better electrochemical performance.When the current density is 200 m A g^-1,its discharge specific capacity is approximately 110 m A h g^-1.And the rate performance is very good,when the current density slowly increases from 200 m A g^-1 to 1 A g^-1,the reversible capacity still has nearly 100 m A h g^-1.According to preliminary investigation,the charging and discharging mechanism of P3,4-Th is based on the intercalation and desorption of Al Cl₄^-large anions.3.Since the conductive polymer has good conductivity,it can be used as a covering material.On the one hand,it can enhance the conductivity of the material and provide a transmission path for Li⁺.On the other hand,it can also provide a three-dimensional network frame to buffer the volume expansion of the inorganic material due to the insertion of Li⁺,and to suppress the chalking of the matrix.In this study,a polythiophene-coated Fe OCl material was synthesized for the first time by chemical oxidation in situ coating method.Use it as a negative electrode material for lithium-ion batteries,when the current density is 100m A g^-1,the first cycle discharge specific capacity is 1764 m A h g^-1,and the initial Coulomb efficiency is low.However,the cycling stability of the battery is good,and the reversible capacity of 796.2 m A h g^-1 is maintained after 350 times of cycling.The rate performance is also very good.When the current density is increased to 2 A g^-1,its reversible capacity is still about 300 m A h g^-1.The coating of polythiophene makes the electrode material more stable and cyclic,has a long cycle life and excellent rate performance.