Donor-acceptor Type Low Band Gap Conductive Polymer As Anode Material For Lithium-ion Battery

In the current society,human beings are facing two main problems:global energy crisis and environmental pollution.With the depletion of fossil fuels and the increasing demand for energy,human beings urgently need to develop new technologies to solve these problems.Among them,lithium-ion battery is a new type of green energy with the most potential and application prospect.However,the electrode materials for lithium-ion batteries have always been inorganic materials.Compared with inorganic materials,organic materials have overwhelming advantages.First of all,organic materials can be recycled and have sufficient reserves,while inorganic materials mostly come from non renewable mineral resources.Secondly,the molecular structure design of organic materials is flexible.In addition,the low price makes it can be applied to all aspects of society.Conductive polymer is a kind of polymer with obvious electron conjugation chain.The donor-acceptor（D-A）type conductive polymer can alternate the electron rich and electron deficient groups in the main chain of the polymer.It is beneficial to the effective transfer of electrons within the molecule,and the delocalization ofπelectrons is enhanced,which can get excellent electrochemical performance.In this paper,a series of low band gap conductive polymers were synthesized by using D-A strategy.In order to increase their conductivity,we prepared composite materials by combining them with activated carbon,and used them as anode materials for lithium-ion batteries.The specific research contents and results are as follows:1.Two D-A polymers were synthesized by Stille coupling with pyrene-4,5,9,10-tetraone（PT）as acceptor,thiophene and 3,4-ethylenedioxythiophene（EDOT）as donors.Subsequently,the polymer and activated carbon were used in-situ polymerization strategy to synthesize PTPT@AC and POTPT@AC.Experimental data shows that POTPT@AC performs better in terms of specific capacity,rate and cycle stability.This may be inseparable from the EDOT unit of the side chain in POTPT.The lower band gap and stronger electron donating ability of EDOT unit may be the reason why its electrochemical performance is better than PTPT.2.Three kinds of D-A polymers were designed and synthesized based on phenanthroline dione.The experimental results show that three materials can be used as anode materials for lithium-ion batteries.It is worth mentioning that by calculating the energy levels from the CV of the three polymers,it can be concluded that the PBTPD with low energy gap has good conductivity,which also corresponds to the fact that PBTPD@AC has the characteristic of high specific capacity.In addition,the mechanism of lithium storage about lithiation/delithiation was verified by X-ray photoelectron spectroscopy（XPS）.3.In this work,two new D-A conductive composite materials PTTBT@AC and POTTBT@AC were synthesized.The POTTBT@AC material has a larger specific surface area,and the conductivity can be improved by adding AC.These characteristics are all conducive to lithium ion storage.When used in lithium-ion batteries,it exhibits high lithium storage capacity and good cycle stability,as well as excellent rate performance and long cycle life.The results show that the excellent electrochemical performance of POTTBT@AC composite is related to the large pseudocapacitance ratio and low energy gap.4.Two polymers are synthesized in this chapter.These receptors of polymers have high charge mobility,which improves the electrochemical and kinetic properties.Besides,the coplanar structure and C=N electron-deficient group greatly improve the polymer properties.Compared with PTTP@AC,the discharge performance of lithium-ion batteries using PTTQ@AC electrode material has been greatly improved,and the discharge specific capacity is 320.1 m Ah g^-1 after 600 cycles of 100 m A g^-1.