Preparation Of Polyaniline-Based Electrode Material And Their Application In Zinc Ion Batteries

Aqueous Zinc Ion Batteries（AZIBs）are the representative of the new type of aqueous rechargeable batteries.It is considered to be a very promising alternative energy storage device for the future development because of the safety and stability of Zn anode,abundant reserves on earth,environmental protection and green water electrolyte,low redox potential and other advantages.The urgent requirement of AZIBs research is to find a suitable cathode.Among many AZIBs cathode materials,conductive polymer has attracted much attention because of its longπ-πelectron conjugated system and its good electron conductivity after doping.Polyaniline（PANI）is a typical conductive polymer,which has been shown to be a good cathode candidate for AZIBs.However,PANI usually requires high proton concentration to facilitate the redox process when acting in aqueous systems,this highly acidic environment is hardly compatible with zinc metal anodes.Therefore,novel PANI modification strategies need to be explored to enhance the high redox activity of PANI in neutral or low-acid electrolytes.In this thesis,PANI was prepared by using micelles formed by surfactant characterized organic acids（salicylic acid,β-naphthalenesulfonic acid and sulfosalicylic acid）as templates,and at the same time,graphite acid（GA）and HClO₄ are used for doping or copolymerization of aniline（An）and aniline derivatives（p-phenylenediamine（PDA））.These methodes provides a feasible solution for the further application of PANI in battery electrode.The specific research content of this thesis is as follows:1.The BHA-PANI/GA cathode material with excellent electrochemical performance was prepared by chemical oxidation method by adjusting the amount of salicylic acid（BHA）to regulate the coordination degree of BHA and Fe³⁺,so as to control the concentration of Fe³⁺in the reaction system stably.The presence of BHA in the form of micelles in solution provides a"soft template"for the polymerization of An monomer,while the presence of abundant oxygen-containing functional groups（-OH,-COOH,etc.）in GA can strongly improve the wettability of BHA-PANI/GA cathode materials,and the presence of-COOH and BHA can enhance the protonation degree of PANI.In addition,the presence of GA can effectively alleviate the volume expansion of PANI during the charge/discharge cycle.Therefore,based on the advantages of the BHA-PANI/GA structure,it can exhibit excellent electrochemical performance as the cathode material for AZIBs with a discharge specific capacity（C_s）of 296.46 mAh/g at a current density of 0.20 A/g,and even at a high current density of 5.0 A/g the C_s is still 135.31 mAh/g.And its C_s can still be maintained 88.21 mAh/g at a current density of 1.0 A/g for 1000 cycles.2.βPG-PANI-6 cathode material was prepared by layer self-assembly electrochemical polymerization strategy.β-Naphthalenesulfonic acid（β-NSA）can form micelles in the electrolyte,and can enter the PANI main chain with HClO₄ to increase the distance between the PANI chain segments,weakening the interaction between the PANI chain segments to improve wettability of cathode material.And the sulfonic acid group can form a"quaternary ammonium salt"structure with some cations on the PANI chain,which can further improve the crystallinity of PANI,while the doping of HClO₄ ensures the excellent conductivity of the cathode material.In addition,GA is rich in-COOH on the surface,which can ensure a low pH environment near the polymer backbone to effectively control the deprotonation of PANI,and also reduce the volume expansion of PANI during the charging and discharging process.At the same time,the surface controlled energy storage mechanism of βPG-PANI-6(Zn²⁺and CF₃SO₃^-)ensures the rapid dynamic migration of charge carriers.The electrode material can show 560.5 mAh/g C_s at A low current density of 0.20 A/g,and can maintain 56.44%of C_s at 1.0 A/g even at a very high current density of 10.0 A/g.In addition,the cathode can show high energy density and power density（535.31Wh/kg@187.16 W/kg and 184.45Wh/kg@7378.01 W/kg）.3.The S-p（ANI-PDA）/GA cathode material with excellent electrochemical performance was prepared by electrochemical copolymerization of An and PDA on stainless steel mesh using cyclic voltammetry strategy under the condition of the co-doping of sulfosalicylic acid（5-Sulfosalicylic acid dihydrate,S-BHA）and HClO₄.The introduction of PDA improves the segment regularity of copolymer.In the preparation process,the amphiphilic structure of S-BHA makes it exist in solution in the form of micelles,thus providing a polymerization template for the copolymerization of An and PDA.In addition,the presence of sulfonic acid root can increase the distance between copolymer chain segments,further ensuring the chain segment regularity and crystallinity,while the doping of S-BHA with HClO₄ and GA can effectively promote the S-p（ANI-PDA）/GA protonation degree and improve its conductivity and cycle life.When S-p（ANI-PDA）/GA was used as the cathode material of AZIBs,its C_s were 363.83 mAh/g and 231.45 mAh/g at 0.20 A/g and 5.0 A/g,respectively,showing a better multiplicative performance.Meanwhile,after long-term cycling tests,it was found that after 500 cycles of charging and discharging at 1.0 A/g,the C_s was still maintained at 189.83 mAh/g,which has a good long cycle life.