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Synthesis And Electrochemical Performance Of 3-dimensional Porous NiCo2O4 Free Standing Electrode Materials

Posted on:2019-06-26Degree:MasterType:Thesis
Country:ChinaCandidate:Y WangFull Text:PDF
GTID:2371330596951002Subject:Engineering
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Despite carbonaceous materials are widely employed as commercial negative electrodes for lithium ion battery,an urge requirement for new electrode materials that meet the needs of high energy and power density,excellent cycle stability,low cost and safety is still underway.A number of transition oxide have been developed over the past years.Their high theoretical capacity,rich redox reaction and adequate cyclability make these materials will become a tangible reality for practical applications in the near future.Fabricating free-standing binary transition metal oxides,especially NiCo2O4,has attracted abundant research interests as promising free-standing anodes of lithium-ion batteries?LIBs?.However,there remain some problems for the existed NiCo2O4anodes,especially the low loading.To address the above issue,it will become a quite feasible solution to connect the advantages of both hierarchical micro/nano-structures and free-standing electrodes to fabricate a free-standing hierarchical micro/nano-structural NiCo2O4 electrode.Herein,we propose an effective method to controllably synthesize hierarchical bilayered hybrid nanostructural arrays of NiCo2O4?HNAs?nanourchins and nanowires based on Ni foam?NF?with a high loading,which is denoted as NiCo2O4 HNAs/NF,via a simple surfactant-assisted hydrothermal and subsequent annealing treatment.In this synthesis,the NF is applied as Ni resource of NiCo2O4 without adding other Ni-included reagent,and the pH value plays an important role for the synthesis of NiCo2O4 HNAs/NF.Furthermore,the formation mechanism of products is in detail discussed.The as-synthesized NiCo2O4 HNAs/NF possesses the unique architectural feature,such as large surface area,A large number of mesoporous and robust connection of NFs and active materials.Therefore,the NiCo2O4 HNAs/NF electrode showed excellent electrochemical performance.Especially,the NiCo2O4 HNAs/NF electrode showed a high loading about 7 mg cm-2,is beneficial to the lightweight and miniaturization of LIBs.Besides,in order to further improve the conductivity and structural stability of electrode,this work propose a controllably in-situ synthesis to coat a thin layer of carbon on the surface of NiCo2O4 HNAs/NF in the premise ensure the same morphology structure remains the same.This work achieved the one-step fabrication of in situ carbon-coated NiCo2O4@C bilayered hybrid nanostructural arrays used by the same experimental method.As the anode of LIBs,it has good structural characteristics and long cycle life.Furthermore,we also use the vanadium oxide coated on NiCo2O4 HNAs/NF,get another kind of porous rose-like NiCo2O4@V2O3@NF micro-nano structure with a different morphology.Its excellent ionic conductivity make the electrode have excellent rate performance.To sum up,these improvements have made have different levels of the electrochemical performance.
Keywords/Search Tags:lithium-ion battery, NiCo2O4, free-standing, micro/nano-structure, high loading, n situ synthesis, vanadium oxide
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