The Preparation Of Flexible Oxide Films And Its Application In Energy Storage Devices

According to the oxygen insertion mechanism proposed by Tyler,the oxygen vacancy in the compound oxide can be considered as native energy storage sites to generate pseudocapacitance.Pyrochlore-type oxides with abundant oxygen vacancies could be applied as huge potentially energy storage materials.When their A-site or B-site were doped with other elements,it was effective to adjust the concentration of the oxygen vacancies and increase the energy storage sites.In this paper,in order to solve the problems in the field of supercapacitor,such as narrow electrochemical window and low energy density,a series of flexible pyrochlore-type oxides(Lanthanum Titanate,La₂Ti₂O_7,LTO)nanofibers with higher energy storage characteristics have been prepared through electrospinning and low-temperature sintering method.Therefore,Sr or Y elements doped in A-site or B-site of La₂Ti₂O₇were studied to improve its electrochemical property and obtain flexible supercapacitor device with high performance.The main research contents are as follows:(1)By investigating the microstructure and morphology of LTO films calcinated in different temperatures,the specific process of electrospinning and calcination was studied carefully and the most suitable sintering temperature was found.By the using of LTO nanofibers as the active electrode materials,electrochemical study was carried out to determine the best electrolyte for LTO.Thus,the LTO nanofibers prepared at the optimal sintering temperature were used as the active electrode materials,combined with the optimal electrolyte to assemble the supercapacitor devices and their electrochemical performance was studied at detail.(2)Conducting a research about B-site doping LTO,a series of Y doped La₂Ti_2-xY_xO₇nanofiber membranes with different doping proportions were prepared by electrospinning method.Then the crystalline phase,microscopic morphology,element composition and electrochemical properties of the nanofibers were studied to comprehensively determine the best Y doping proportion(X=0.2)by XRD,SEM and TEM technique.The nanofibers with the best Y doping ratio were used as active electrode materials to prepare flexible electrode and supercapacitor devices,and their electrochemical performance was studied systematically.(3)Making a research about A-site doping LTO,a series of La_2-xSr_xTi₂O₇ nanofiber membranes doped with Sr were prepared by electrospinning method.Then the crystalline phase,microscopic morphology,element composition and electrochemical properties of the nanofibers were studied to comprehensively determine the best Sr doping proportion(X=0.3).Finally,using nanofibers with the best Sr doping ratio as the active electrode materials,the flexible supercapacitor devices were prepared to study the electrochemical performance.Compared with previous research results,the best doping plan was determined.All in all,a series of pyrochlore-type nanofibers with good flexibility and high electrochemical activity have been prepared through electrospinning and used as the electrode active materials.Research has been shown that A-site or B-site suitable doping could effectively improve electrochemical property,thereby obtaining high performance flexible supercapacitor device.