Study On Preparation And Energy Storage Performance Of Porous Organic Polymers Based On Polycarbonyl/Nitrogen Heterocyclic Groups

In the pursuit of a next-generation energy storage system with renewable and clean energy,organic electrode materials have received great attention as high-performance future electrode materials due to their structural diversity,low weight,environmental sustainability and mechanical flexibility.However,their high solubility in aprotic electrolytes,inherent low conductivity and low active site utilization limit their application in large-scale energy storage systems.At present,the construction of polymers containing multiple active sites and conductive polymers through molecular engineering is the main research strategy to suppress solvent problems and improve conductivity.In this thesis,a series of organic polymers have been synthesized and designed based on the strategy of adjusting the redox centers,constructing multifunctional groups andπ-conjugated systems and adding conductive materials based on small molecular polycarbonyls and nitrogen-containing heterocyclic organics.The obtained electrode materials effectively solve the problem of the solubility of small molecular organics in the electrolyte,and improve the electrochemical performance of the material.The main research contents and conclusions are summarized as follows:1.Pyrene-4,5,9,10-tetraketone（PT）-based polycarbonyl linear polymers（PPTS）were synthesized with thioether bonds as bridging groups and used as anode materials for lithium ion batteries（LIBs）and sodium ion batteries（SIBs）.The PT unit has abundant redox active carbonyl groups and supports reversible redox reactions.The introduction of a large number of S atoms can effectively improve the conductivity of the material.Due to fast reaction kinetics,accelerated lithium ion and electron transport capabilities,and stable amorphous framework,PPTS shows improved conductivity and insolubility in non-aqueous electrolytes.When used as an anode material for LIBs,PPTS delivers a high reversible specific capacity of 697.1 m Ah g^-1 at 0.1 A g^-1 and good rate performance(335.4 m Ah g^-1 at1 A g^-1).Moreover,a reversible specific capacity of 205.2 m Ah g^-1 at 0.05 A g^-1 and good rate performance could be obtained as the anode material for SIBs.2.Two kinds of nitrogen-rich porous polymers（TAPT-TPA and TAPT-BTPA）were synthesized by Schiff base reaction based on the triazine skeleton-containing compound4,4,4-（1,3,5-triazine-2,4,6-triyl）trianiline（TAPT）and used as electrode materials for LIBs and SIBs.The abundant triazine ring and imine structure can be used as active sites to support reversible redox reactions.In addition,the introduction of the electrophilic triazine ring can effectively adjust the energy level and energy gap of the molecular orbital,and further adjust the electron transport capacity and redox potential.In order to further improve the active site utilization of polymers,they were integrated with CNT.The prepared composite material not only solves the problem of easy dissolution of small molecules,but also significantly improves electrochemical performance.When used as a anode material for LIBs,TAPT-BTPA@CNT with a larger pore size achieves high rate performance(provides a discharge specific capacity of 177.9 m Ah g^-1 at 5 A g-1)and stable cycle performance(a specific capacity of 350.9 m Ah g^-1 can be gained after 1000 cycles at1 A g^-1).As the anode material for SIBs,it also provides high initial reversible charge specific capacity(253.3 m Ah g^-1)and excellent capacity retention rate.3.Based on TAPT and two aromatic dianhydrides,1,4,5,8-naphthalenetetracarboxylic anhydride（NTCDA）and 1,2,4,5-pyromellitic anhydride（PMDA）,two types of polyimide（PI）-based conjugated microporous polymers（CMPs）have been synthesized（TAPT-NTCDA and TAPT-PMDA）,which have abundance carbonyl and nitrogen-containing heterocyclic triazine skeleton.Then the obtained polymers are integrated with CNTs as electrode materials for LIBs and SIBs.The prepared composite material not only solves the problem of solubility,but also significantly improves the utilization of active sites.Among them,naphthyl-based TAPT-NTCDA@CNTs provided high initial discharge capacities(for LIBs:155.5 m Ah g^-1 at 0.05 A g^-1;for SIBs:91.9 m Ah g^-1 at 0.03 A g^-1)and long-cycle stability(for LIBs:87.3%capacity retention after 500cycles at 1 A g^-1;for SIBs:provide a specific discharge capacity of 70.3 m Ah g^-1 after 200charge-discharge cycles at 0.03 A g^-1)when used as cathode materials for LIBs and SIBs.Moreover,TAPT-NTCDA@CNT still has good electrochemical performance when used as an anode material for LIBs.Based on this,TAPT-NTCDA@CNT can also be used as both cathode and anode material to assemble all-organic symmetrical batteries,which can also achieve excellent cycle stability and rate performance.4.In this chapter,we reported the synthesis,characterization and lithium ion storage properties of carbonyl-containingπ-d CCPs,which use tetraaminobenzoquinone（TABQ）as the organic ligand and M²⁺（M=Co,Ni,Cu）as the metal ligand.The as-obtained M-TABQ shows insolubility in organic electrolytes and electron delocalization structure,which have been confirmed by the detailed characterizations.The conjugated benzoid carbonyls andπ-d hybridization center as redox sites can reversibly react with Li-ions,which are also confirmed by theoretical calculations.Among them,Ni-TABQ shows the higher conductivity and best electrochemical performance,when used as a cathode material in lithium-ion batteries（LIBs）,it delivers a high initial discharge specific capacity of 318.7m Ah g^-1 at 50 m A g^-1,and good rate performance(even 237.2 m Ah g^-1 at 2 A g^-1).The reason for the superior performance of Ni-TABQ as well as its lithium ion storage mechanism is verified by theoretical calculation and spectroscopic characterization.Encouragingly,Ni-TABQ can be served as both cathode and anode materials to construct high-performance all-organic symmetric LIBs,which delivers high power density up to 142Wh kg^-1 with stable cyclability for 100 cycles at 200 m A g^-1.More importantly,the flexible all-organic pouch LIBs assembled by Ni-TABQ also show stable electrochemical properties under different bending states,demonstrating its great potential in the field of flexible wearable devices.