Study Of Noveal Two Dimensional Layered Nano-materials And Three Dimensional Network Structures’ Preparation, Characterization And Electrochemistry Energy Storage Applications

Lithium-ion batteries and supercapacitors are indispensable electrochemical energystorage devices in the modern production and living of society. One of the primaryissues in the future social development is to exploit electrochemical energy storagedevices with high energy density and high power density, and the effective way toachieve this lies in development and structure design of new types of active electrodematerials. This paper initiatively puts forward the usage of two-dimensionalgraphene-like layer materials to design special device structure (planarmicro-supercapacitor) and electrode materials with network structure. The planarmicro-supercapacitor based on MoS2was successfully achieved and electrode materialsof V2O5and V2O5@PPywith three-dimensional network structure, as well as ofCoO/graphene composite material with carpet-like structure were prepared. The crystalmorphologies and compositions of the materials were detected by XRD, SEM, TEMand XPS. The performances of the symmetric/asymmetric supercapacitor andlithium-ion batteriey based on those materials were studied. The main contents are asfollows：①Two-dimensional MoS2nanosheet was achieved by hydrothermal and theliquid phase separation methods. The planar micro-supercapacitor based on thematerials exhibited excellent areal (~8mF cm-2) and volumetric capacitances (178Fcm-3) a well as good cycling stability (only~8%loss after1000cycles test). Inparticular, the areal capacitance was better than those of micro-supercapacitors based oncarbon materials (onion-like carbon and graphene) reported in the literatures. Thisresearch has not only expanded the applications of two-dimensional graphene-likematerials in the fields of energy storage, but also provided a simple and facile method tofabricate other two-dimensional layered structures materials.②Three-dimensional network structure aerogels of self-assembly V2O5nanosheetand nano ribbon were innovatively prepared by hydrothermal and freeze dryingmethods, respectively, both of which have high specific surface area and uniform poresize distribution as new three-dimensional porous materials. The symmetricsupercapacitor composed of V2O5nanosheet with three-dimensional network structureshowed ultrahigh specific capacitance (521F g-1), excellent cycling ability, high energydensity (247.9Whkg-1) and power density (39.9kWkg-1). Moreover, the three-dimensional network of V2O5@PPycomposite was prepared successfully bycasting method, and the the asymmetric supercapacitor, composed of V2O5@PPyaspositive electrode and chemical reduction graphene oxides with three-dimensionalnetwork structure as negative electrode, had the cell voltage of1.8V and it reached upto an maximum specific capacitance of186F g-1and an energy density of21Wh kg-1.In practical testing, after charging two such asymmetric supercapacitors couldeffectively power a red round indicators(2.0V,20mA) for5minutes, which furtherdemonstrated the practical application merit of the material.③The vertical growth of one-dimensional CoO nanowires on three-dimensionalnetwork structure graphene nanosheet was achieved by a simple wet chemical method(hydrothermal) for the first time in our paper and CoO/graphene composite materialswas successful prepared. The materials has an interconnected electrical network,hierarchically porous structures and carpet-like morphology. When used as cathodematerial for lithium-ion battery, it can ensure rapid migration of the electrons and ionsin the process of charging and discharging. The capacity was1483.1mAhg-1at thecurrent density of74mAg-1, which was higher than CoO nanowires. In addition, thecomposite material revealed excellent cycling performance, rate capability andcoulombic efficiency. The results in this paper demonstrated that the electrochemistryproperties of the whole system was improved compared with control sample after theintroduction of three-dimensional network structure graphene.We believe that the simple and green method in this paper used to prepare novelthree-dimensional network structure of self-assembly two-dimensional graphene-likematerials could open up a new and versatile way to prepare and design new electrodematerials, which are expected to be widely applied in the field of energy storage,sensors and catalysis.