Solvothermal Synthesis And Electrochemical Properties Of CH₃NH₃PbX₃?X=I,Br?

In the past ten years,the organic-inorganic hybrid perovskite CH₃NH₃PbX₃material has been a hot topic.Research on lithium storage using halide perovskites has been initiatedhalide perovskite based electrodesexhibit high stability during electrochemical cycling without any structural rearrangement.However,how to effectively control the electrode material structure and particle size is still a key scientific problem for realizing the ideal negative electrode material for lithium ion batteries.Therefore,this dissertation uses solvothermal method to control the preparation of CH₃NH₃PbX₃?X=Br,I?electrode materials,and to explore its growth mechanism and stability,and provides a theoretical basis for the development of electrode materials with stable removal/intercalation ability.Through the design of the process parameters,the self-assembly mechanism and the dissolution-etching mechanism of the crystal structure were studied.In this paper,CH₃NH₃PbX₃ crystals were prepared by solvothermal method using lead acetate,hydroiodic/hydrobromic acid,methylamine as raw materials and isopropyl alcohol as solvent.SEM,XRD,FIIR,DRS,PL and other test methods were used to study the perovskite morphology,crystallinity and composition.The results show that high-quality CH₃NH₃PbI₃ crystals can be obtained when the synthesis temperature is120°C and the reaction time is 4 h.When the synthesis temperature is 150°C,the reaction time is 15 h,and the lead ion concentration is 0.5 mol/L,the highest quality of CH₃NH₃PbBr₃ crystals is obtained.The Ostwald ripening growth mechanism was used to study its growth process,and it was found that the directional self-assembly mechanism played a major role.For further study of the influence of electrode material structure and particle size on its electrochemical performance,The CH₃NH₃PbX₃ electrode material was assembled into a battery.The electrochemical properties of the CH₃NH₃PbX₃ electrode were studied by charge-discharge test,cyclic voltammetry,and electrochemical impedance spectroscopy.The results show that the CH₃NH₃PbI₃ synthesized for 4 h has the best crystallinity and electrochemical performance.After 50 cycles of charge and discharge,the capacity retention rate is 65%.The size of 1.2 mm CH3NH3PbBr3 has the smallest particle size,the fewest defects,and the best electrochemical performance.The repeatability is very good.After 50 cycles of charge and discharge,the capacity retention rate is 77.5%.