| Transition metal oxide has the advantages of high theoretical capacity,abundant resource reserve,environmental friendliness and high safety,and is one of the candidates for anode materials of lithium ion batteries.However,the poor conductivity of transition metal oxides and the large volume expansion of lithium ions when intercalation deintercalation are easy to cause energy storage failure and structural collapse.To solve this problem,the commonly used improvement methods are the synthesis of nanoscale transition metal composites and modification treatment such as coating and doping.Although a good improvement has been achieved,there are still many problems in the practical application of transition metal oxide-based anode materials.In this paper,the sandwich composite alloy was obtained by the metallurgical process,and the nanoporous electrode was prepared by dealloying technology.Through in situ deep oxidation to improve the active oxide load,low-temperature reduction to create defects,and carbon coating to improve carrier density and structural stability,high performance lithium ion battery integrated electrode was prepared.This method is beneficial to more reasonable surface structure construction and stronger electron/ion transport capability,which makes up the gap between theoretical design and actual regulation to some extent and has great research potential.The thesis mainly contains all the results as follow:(1)Controlling the growth of metal oxides on nanoprous NCo Mn alloys for lithium-ion storage research.The sandwich structure NiCoMn-Cu-NiCoMn alloy foil strip,dealloying process to form flexible nanoporous NiCoMn-Cu(npNCM-Cu)precursor.The R-npNCM-Cu electrode was obtained by heat treatment for 1 h under the condition of hydrogen gas.The diameter and ligament size of the R-npNCM-Cu electrode treated at 400?were similar,which was conducive to the subsequent oxide load and ion diffusion.Oxides can be grown in situ on the surface of the nanoporous metal through air treatment and a high-load integrated nanoporous alloy@oxides electrode(npNCM-Cu)was obtained.It was found that the dealloyed npNCM-Cu alloy reduced for 1 hour at 400?and the electrode oxidized for 2 hours at 300?was formed through hydrothermal carbon coating(C@npNCM@oxides-Cu)with the optimal electrochemical performance.That is,at the current density of 0.5m A cm-2,its capacity can reach 9.47 m Ah cm-2.(2)Study on the Lithium storage performance of NiCuMn Carbon coating and Cu doping synergically enhanced Electrode.The sandwich structure:NiCuMn-Cu-NiCuMn alloy,the nanoporous structure formed after the dealloying treatment has ultra-high surface energy,and the oxygen induced from the air generates self-combustion to form the nanoporous electrode with high oxide load(NiCuMn@oxides-Cu).In this study,it was found that low-temperature reduction in hydrogen atmosphere was beneficial to increase carrier concentration in the oxide layer and generate more vacancies/defects,thus improving structural conductivity and cycling stability of the battery.Carbon coating modification shall be applied to the surface of the C@A-NiCuMn@oxides-Cu electrodes,and amorphous carbon coating shall be formed.The capacity can still be maintained at 4.15 m Ah cm-2 after 100 cycles.The self-combustion process is conducive to the rapid increase of the active material load,low-temperature reduction to create more defects,improve the conductivity of the oxide layer,and reactive sites.Finally,carbon coating plays a further role in cushioning volume expansion. |
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