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Electrodeposition of3D-porous Ni/NiO Films Using Hydrogen Bubbles as a Template and Lithium-ion Inte

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Tutor: ZhangNaiQing
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Lithium ion batteries,Anode materials,3-D porous Ni/NiO film,Hydrogen Bubbles Te
CLC: TM912
Type: Master's thesis
Year:  2012
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Abstract:
Advanced Rechargeable lithium-ion batteries £¨LIBs£© hold great applicationsfor use in portable electronics, power tools, electric and hybrid vehicles,renewable energies, due to their high energy density, high power density, longlifespan and environmental friendliness. The lithium-storage performances ofLIBs are determined by the properties of electrode materials, including theirspecific capacities, cycling, rate and safety. The commercial anode materials ismain carbon, with low specific capacity(375mAh¡¤g-1)containing graphite andcoke, don¡¯t meet the requirements of high energy and power density of LIBs forelectric and hybrid vehicles. Nickel oxide £¨NiO£©, as an important transition-metaloxide, is considered as a very appealing anode material for LIBs, owing to thehigh theoretical capacity (718mAh¡¤g-1), low cost, high safety and environmentalbenignity. In this paper, to improve the initial coulombic efficiency, cycling andrate performance of NiO, we designed a novel3D porous micro/nano-structuredinterconnected £¨3D PMNI£© Ni/NiO via a H2bubbles dynamic template route.Firstly,3D porous micro/nano-structured foam Ni was prepared on thestainless stell sheet £¨304SS£© substrates by the strong cathodic electrodeposition.During the process of electrodeposition,304SS acted as working and counterelectrodes, H2gas bubbles originated from the cathodic reaction on the substrateas a dynamic pore-forming template, NiCl2and NH4Cl solutions as electrolyte.3D porous micro/nano-structured foam Ni was obviously influenced by thesefactors, such as the concentration of electrolyte, current densities, time andadditives. Experimental results demonstrated that3D porousmicro/nano-structured foam Ni with the pore of5-10¦Ìm was obtained in thecurrent density of4A¡¤ cm-2for20s in0.02mol¡¤L-1NiCl2and1mol¡¤L-1NH4Clsolutions.Secondly,3D porous micro/nano-structured foam Ni was converted to3DPMNI Ni/NiO by partially thermal oxidization in air. The temperature and timeof thermal oxidization had an apparent effect on the structure of3DPMNINi/NiO. Lowing400¡æ,3D porous micro/nano-structured foam Ni was hardlyoxidized, and exceeding600¡æ,3D porous Ni was oxidized and nanoparticles in3D porous structures were seriously aggregated. Results shown that3D porousNi could be perfectly transformed into3DPMNI Ni/NiO at450¡æfor2h, whichconsisted of interconnected pores, and microparticles with the size of ca.240-350nm originated from the aggregation of interconnected Ni and NiOnanoparticles of ca.10-20nm. As the integrated anodes of LIBs,3DPMNI Ni/NiO delivered high-rate capacity of675mAh¡¤g-1at20C rate and763mAh¡¤g-1after100cycles at1C rate.The super rate and cycling performance of3D PMNI Ni/NiO might beascribed to the unique3D porous micro/nano-interconnected structures:1.3DPMNI Ni/NiO with nano-components provide a high surface area to enlarge theeffective electrode materials/electrolyte contact, resulting into moreelectro-active sites for lithium-storage.2.3D porous microstructure wasconsiderably mechanical stability, and used as a structural buffer for the largevolume variation during the discharge-charge process.3.3D porous metalnanoparticles acted as both the3D conductive network scaffold to provide ahighly conductive pathway for electrons and the catalyst of the conversionreaction to enhance the reverse reaction to the degree.
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