Study On The Synthesis Of Triazine-Based Conjugated Microporous Polymers And Their Lithium/Sodium Storage Properties

Although the continuous exploitation of fossil fuels has brought prosperity and development to mankind,but at the same time,it has also led to problems such as energy crisis and environmental pollution.In order to solve these problems,people have gradually started to explore sustainable and clean energy systems,such as fuel cells,solar cells and rechargeable batteries and other energy storage devices.Among them,lithium-ion batteries（Lithium-Ion Batteries,LIBs）have been very successful in portable electronics due to their high energy density and have great potential in the field of electric vehicles.However,the high cost of lithium and limited resources have hindered its use in large energy storage devices.Therefore,there is an urgent need to develop other materials that can replace lithium and assemble energy storage devices with comparable or better performance than LIBs.Sodium is of great interest because of its abundance in nature,low cost and sustainability,thus Sodium Ion Batteries（SIBs）can be expected to be the next generation of energy batteries.While inorganic electrode materials commonly used in LIBs and SIBs contain transition metals,their development has been limited by limited resources and environmental unfriendliness.Compared with inorganic materials,organic materials have the advantages of low cost,environmental friendliness,and ease of improving battery performance through molecular structure tuning.In this paper,a conjugated microporous organic polymer（CMP）as well as a covalent organic framework（COF）were synthesized and their electrochemical properties as negative electrode materials in LIBs and SIBs were investigated as follows:（1）A conjugated microporous polymer（PTB）was synthesized by solvent-free polymerization of[2,2’-bithiophene]-5,5’-dicarbonitrile（Bt DCB）monomer catalyzed by P₂O₅.PTB exhibited considerable specific capacity and rate performance after activation.As an anode material for LIBs,the specific capacity is as high as 1014 m Ah g^-1 at a current density of 0.1 A g^-1,and a specific capacity of 486 m Ah g^-1 can still be achieved after a long cycle of 1000 cycles at 5 A g^-1.Meanwhile,PTB also shows excellent electrochemical performance in SIBs,with high specific capacities of 425/260/156 m Ah g^-1 at current densities of 0.1/1/5 A g^-1,respectively.This result exceeded all the currently reported CMP-based SIBs anode materials.In addition,the performance of the assembled SIBs even exceeds that of most COFs anode materials at high current densities.（2）The poly（triazine-imide）（PMBA-MA）and in-situ grown（PMBA-MA@CFC）COF materials were synthesized by using pyromellitic dianhydride（PMBA）,melamine（MA）,and carbon fiber cloth（CFC）as raw materials and N,N-dimethylformamide and ethylene glycol as mixed solvents.For PMBA-MA,the initial discharge specific capacities of LIBs/SIBs were1084.69/970.17 m Ah g^-1 at a current density of 0.1 A g^-1,respectively,and the discharge capacities were 377.8/288.33 m A h g^-1 after 100 cycles,respectively,which were also poor in rate performance.For the in-situ grown PMBA-MA@CFC,the electrochemical performance of the cell was significantly advanced,and the discharge specific capacities of LIBs and SIBs could reach 575.65 and 394.02 m A h g^-1,respectively,after 100 cycles.This work provides a novel idea for the modification of COF anode materials.