Design, Synthesis And Application Of Electrode Materials Based On Organic Polymers

Rechargeable LIBs have become the most widely used secondary battery system due to their excellent electrochemical performance.Organic electrode materials make lithium storage systems have the characteristics of low cost,flexibility,sustainability,high redox activity,good electrochemical reversibility,and high energy density.For example,quinone compounds have become one of the most promising organic materials for energy storage due to their advantages such as higher theoretical energy density.Due to the advantages of the porous structure,conjugated porous polymers further enhance the regulation of ion diffusion and insertion,which have received special attentions.In this regard,this thesis focuses on the design and synthesis,microscopic morphology,structure,and energy storage applications of polymer materials.The specific contents are as follows:(1)We have prepared polyanthraquinone sulfide(The anthraquinone units are connected by thioether bonds and polymerized,PAQS)using a one-step condensation method and in-situ chemical solution method and a series of polyanthraquinone sulfide/carbon nanotube composite materials(PAQS/CNT).PAQS/CNT is a three-dimensional honeycomb structure with abundant pores.The PAQS/CNT framework material containing 2% carbon nanotubes has a good electrochemical performance.At a rate of 0.2 C,the initial discharge specific capacity is 187.2 m Ah/g,which is significantly higher than that of the pure PAQS electrode(101.0 m Ah/g).After 200 cycles,the specific capacity remains 168.4 m Ah/g,and the retention rate is90.0%.It was confirmed that CNTs act as a skeleton in the polymer material,thereby stabilizing the structure of the polymer material during battery charging and discharging,improving electronic conductivity,and inhibiting the dissolution of the material in the organic electrolyte.(2)An anthraquinone-based conjugated organic conductive polymer—polyvinylanthraquinone(the anthraquinone units are connected and polymerized with carbon-carbon double bonds,PEAQ)was synthesized by the famous olefin metathesis reaction.This conductive polymer was assembled into a lithium half-cell for electrochemical performance test.Pure PEAQ provides an average working voltage of 2.14 V and an initial capacity of 124.9 m Ah/g,as well as a stable cycle capacity(the capacity retention rate of 38.4% after 200 cycles at the rate of 0.2 C).PEAQ is also copolymerized with carbon nanotubes.The PEAQ/CNT-2which contains 5% CNTs provides a higher initial capacity of 149.9 m Ah/g and more stable cycling capacity(the capacity retention rate of 52.5% after 700 cycles at the rate of 100 m A/g).CNTs support the PEAQ material as a skeleton and increase the electron transmission path.(3)A poly Schiff base polymer(PI)connected by C=N bond was prepared by a one-step condensation method using p-phthalaldehyde and p-phenylenediamine as raw materials.Furthermore,PI/CNT composite materials were prepared by addition1%,2% and 5% of CNT respectively.Compared with PI owning a sheet stacking structure,the PI/CNT-3 material with 5% of CNT has a three-dimensional structure formed by CNTs as the frame,and shows excellent electrochemical performance.The PI/CNT-3 material has a specific capacity of 209.9 m Ah/g in the first round.After 200 cycles,the specific capacity can maintain 60.5%.When the charge and discharge rates are 0.1 C,0.2 C,0.5 C,1 C,and 0.1 C,PI/CNT-3 electrode materials exhibit specific capacities of 182.4 m Ah/g,150.8 m Ah/g,129.8 m Ah/g,101.3 m Ah/g,and 156.4m Ah/g,respectively,showing good cycle stability and rate performance.