Preparation Of Phenazine Derivatives And Its Electrochemical Properties

Aqueous zinc-ion batteries（AZIBs）are an ideal choice for energy storage equipment due to its high safety,low manufacturing cost and large theoretical capacity.As a component of AZIBs,cathode materials play an important role.Organics are suitable as AZIBs electrode materials due to their wide sources,diverse structures,environmental friendliness and low cost compared to inorganics.Phenazine compounds have a high theoretical capacity and suitable redox potential and can be used as electrodes in ion batteries,but dissolution of the active material and poor conductivity lead to a rapid decrease of the capacity.In order to solve the above problems,three phenazine derivatives were synthesized by molecular polymerization,extending conjugated structure and introducing electron-withdrawing groups.Their electrochemical behavior as cathode materials for AZIBs were explored and the zinc storage mechanisms were also characterized by ex situ characterizations of Fourier transform infrared（FT-IR）spectra,Raman spectra,X-ray photoelectron spectroscopy（XPS）and Scanning electron microscope-energy dispersive spectrum（SEM-EDS）.The specific study is as follows:（1）In view of the problem of easy dissolution of active materials,poly（2,3-diaminonaphthalene）polymer（PDAN）was successfully synthesized by employing molecular polymerization and used as cathode for AZIBs.Meanwhile,its electrochemical performance in different electrolytes were also investigated.The results showed that PDAN electrode performed optimally in 1 M Zn（CF₃SO₃）₂ with high rate capability(58.4 mA h g^-1 at 10 A g^-1)and excellent cycle stability(69.7 mA h g^-1 after 1000 cycles with a capacity retention of 88.7%at 1 A g^-1).The results of ex-situ characterizations（FT-IR,Raman,XPS and SEM-EDS）proved that the C=N bond in PDAN is Zn²⁺storage site in the electrochemical reaction process.（2）In order to further improve the electrochemical performance,benzohexaazabenzene（BBQP）were successfully synthesized using the extended conjugated structure strategy as the cathode for AZIBs.Benefiting from the extendedπ-πconjugate structure,the characteristics of insoluble electrolyte and the high capacitance contribution rate,BBQP electrode exhibited excellent rate performance(66.6 mA h g^-1 at 10 A g^-1)and outstanding long cycle life(112.5 mA h g^-1 after 2000 cycles at 1 A g^-1).In addition,the results of ex-situ characterization（FT-IR,Raman,XPS and SEM-EDS）confirmed that the C=N bond in BBQP is the active site in the Zn²⁺storage process.（3）To improve the specific capacity,rate capability and atomic utilization of organics,carboxylic acid substituted hexaazabenzene（HATTA）was designed and successfully synthesized by introducing electron-withdrawing groups and used as cathode for AZIBs.Due to the introduction of the electron-withdrawing conjugated group（-COOH）,extendedπconjugated structure and rich active sites,HATTA electrode shows excellent specific capacity(225.8 mA h g^-1 at 0.05 A g^-1),decent rate capability(136.1 mA h g^-1 at 25 A g^-1)and ultra-high cycle life(84.07%capacity retention at 25 A g^-1 after 10000 cycles).Besides,the mechanism of the Zn²⁺storage for HATTA was explored through ex-situ characterization（FT-IR,Raman,XPS and SEM）and reveal that the C=N bond is the active site.Additionally,the flexible Zn/HATTA battery also showed good flexibility and decent long cycle life,demonstrating its promising application in wearable electronics.