| The performance of lithium batteries depends largely on the cathode material,the current inorganic cathode material has the following problems:non-renewable metal as a raw material,cause environmental pollution,problems in safety.Organic cathode material has advantages in fund of raw materials,environment friendly,easily in tructural design and others,and organic cathode material is considered a very promising lithium battery energy storage material.Organic materials can be includes small molecule organic materials and polymer organic materials,and small organic molecules have relatively high theoretical specific capacity,but soluble in the electrolyte,the poor circulation performance,the organic polymers have the relative longer chains of the polymers,which can effectively reduce the dissolution of the cathode material in the electrolyte loss,improve battery life cycle.Based on this,this paper aims to obtain a polyimide polymer with good conductivity by simple preparation method,and explore different preparation methods,different ratio of polyimide and conductive agent,different monomers and other factors,prepare the cathode material with outstanding electrochemical performance in lithium batteries.Based on the above discussion,the research contents of this paper is designed as follows:?1?Polymerization of precursor polyamic acid with in situ polymerization using pyromellitic dianhydride?PMDA?and p-phenylenediamine?p-PDA?as monomers and N-methylpyrrolidone?NMP?as solvent,the precursor mixed unifromly with conductive agent carbon black and under high temperature,through condensation reaction to obatain polyimide/carbon black composite?PI-CBs?.Specifically,PMDA is dissolved in NMP solvent,stirred at room temperature until the solid PMDA is completely dissolved in the solvent,and equimolar p-PDA is added and stirred at room temperature to obtain a prepolymer PAA solution.Then the different proportions of conductive carbon black are added into the PAA solution,the polyamic acid chain is fully compounded with the carbon black.Finally aboved mixture heated at a high temperature for condensation reaction to obtain PI/CBs.As the cathode electrode material of lithium-ion battery,the best sample PI/CB-4 has a the discharge specific capacity of 182 mAhg-11 in density of 100 mA g-1,which is very close to that of the theoretical specific acpacity follws two-electron system.Meanwhile,PI/CB-4 has an ultrahigh capacity of 116 m Ah g-11 at the high current of 10A g-1.In terms of cycle stability,the 80.7%of initial specific capacity can still be maintained after 300 cycles at a current density of 300mA g-1.This result is obviously superior to the previous reports that the polyimide based on PMDA is used as the cathode electrode material in lithium ion/sodium ion battery.At the same time,PI was obtained by using PMDA and rigid p-PDA for the first time,and the organic lithium cathode material with excellent electrochemical performance was obtained.The innovation and superiority of the in situ polymerization method were proved.?2?This paper also explores the preparation of polyimide composite based on perylene anhydride?PTCDA?and different diamine monomers by in-situ polymerization for lithium/sodium cathode.The aim of this paper is use low-cost?facile?controllale methode to prepare polyimide based on PTCDA,and investigate the effect of the different morphologies and structures on the electrochemical performance of polyimide.In this chapter,PDI-EDA/CB,PDI-TDA/CB,PDI-HDA/CB were prepared by in-situ polymerization using ethylenediamine?EDA?,propylenediamine?TDA?and hexamethylenediamine?HDA?.We obtained the PDI-EDA/CB composites with excellent charge and discharge performance.PDI-EDA/CB achieves excellent rate performance of 100 m Ah g-11 at a very high current of 5A g-11 in lithium-ion battery cathode materials. |
PDF Full Text Request