| In modern society,with the increasing demand of energy,larger capacity and higher power energy storage equipment are demanded for pratical application.Due to the small size effect,quantum size effect,surface effect and macroscopic quantum tunneling effect,nanometer materials have been widely studied.Meanwhile,nanometer materials have been widely applied in all areas of the field of technology.Meantime,it has been regarded as the core technology of the next generation energy devices.In the field of energy technology,nano array materials have attracted more and more attention by many researchers due to its superior performance.Its special performance is:(1)it provides direct electronic transmission channel and improves the conductivity of electrode material.(2)It reduces the ion diffusion path in the active material and therefore enhanced the rate capability of the material.(3)Though huge surface area,it increase the electrode and the electrolyte contact area and reduces the charge and discharge time.(4)The structure of nano array is more stable,which withstand greater volume expansion and mechanical degradation.(5)Directly grown on the current,it can be used without conductive additives and binder.(6)The relatively free morphology is easier to construct composite with other material,which will generate synergistic effect between different materials.(7)Compared to the powder material,nano array material has a stable structure,which will pay less influence on the environment and make the electrode more safety.1.Throughing a simple hydrothermal methodO we synthesis the MnO2 nano array films on the carbon substrate.In order to improve the electrical conductivity of MnO2 material,a new kind of MnO2/PPy nanocomposite thin film material was designed.With the improvement of the conductivity and the stability,the electrochemical performance of the system is greatly improved,especially the rate performance and the cycling stability of the materials.Through the impedance analysis of MnO2 nanomaterials in different solid electrolytes,we obtained the best H3PO4/PVA gel electrolyte.The electrolyte not only help the performance of MnO2 materials,but also make the MnO2/PPy composite material more practical.Further more,in order to further study the practical application of this electrode material,we assembled it into a solid symmetrical supercapacitor.Thanks to the superior performance of the electrode material and the stability of the electrolyte,the capacitor exhibits excellent performance that it achieve the highest energy density of 2.04 Wh cm-2 and the highest power density of 0.432 mW cm-2.At the same time,it maintains 93.2%of the initial capacity under the voltage range of 0-0.8 V,which proves that the MnO2/PPy nanocomposite thin film has high stable electrochemical performance.2.Through the research on growth mechanism of ZnO,we successfully master the controllable grown technique of ZnO nanowire arrays,and tens of microns longth ZnO nanowire arrays are obtained.By further experiments,we load a large amount of MnO2 active material on the surface of the ZnO nanowire array.Through the research of growth conditions and subsequent electrochemical performance of the ZnO/MnO2,we successfully screened a ZnO/MnO2 hybrid nanowire array materials with high mass on unit area,which greatly improves the practicability of MnO2.By further electrochemical tests,we confirmed the excellent electrochemical properties of the material.The electrode material has a maximum capacity of 112 mF cm-2,and it maintains the capacity of 81 mF cm-2 after 1000 cycles,which shows excellent electrochemical stability.The electrochemical properties of the thin film electrode are much higher than the conventional thin film electrode materials,which makes the electrode material more valuable.3.A novel synergistic TiO2/MoO3 core-shell nanowire array anode has been fabricated via a facile hydrothermal method followed by a subsequent controllable electrodeposition process.The nano-MoO3 shell provides large specific capacity as well as good electrical conductivity for fast charge transfer,while the highly electrochemically stable TiO2 nanowire core(negligible volume change during Li insertion/desertion)remedies the cycling instability of MoO3 shell and its array further provides a 3D scaffold for large amount electrodeposition of MoO3.In combination of the unique electrochemical attributes of nanostructure arrays,the optimized TO-MO hybrid anode(mass ratio:1:1)simultaneously exhibits high gravimetric capacity(670 mAh g-1;approaching the hybrid's theoretical value),excellent cyclability(>200 cycles)and good rate capability(up to 2000 mA g-1).The areal capacity is also as high as 3.986 mAh cm-2,comparable to that of typical commercial LIBs.Furthermore,the hybrid anode was assembled for the fi rst time with commercial LiCoO2 cathode into a Li ion full cell,which shows outstanding performance with maximum power density of 1086 W kg total-1(based on the total mass of the TO-MO and LiCoO2)and excellent energy density(285 Wh kg total-1)that is higher than many previously reported metal oxide anode-based Li full cells. |
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