| Non-renewable energy sources such as coal,oil,and natural gas have disadvantages of intermittency and nonrepeatability,which have stimulated interest in research on renewable energy sources.The search for suitable energy storage devices has become an urgent task at present.Rechargeable batteries with the advantages of repeatability,environmental friendliness and long cycle life are superior to other energy storage devices.Among them,Research and development of lithium-ion batteries(LIBs)is becoming mature and are widely used commercially.In order to reduce cost and improve the relationship between energy and the environment.Sodium-ion batteries(SIBs)are similar to lithium-ion batteries in terms of energy storage mechanism,and sodium resources are widely distributed and low-cost,which to a certain extent make up for the disadvantages in lithium-ion batteries.According to relevant news reports,China is rich in molybdenum source reserves,accounting for about 44%of the global molybdenum source reserves.Therefore,the study of molybdenum-based materials has certain strategic significance.Molybdenum-based materials have variable valence states,complex reaction types and rich structural types,exhibiting different types of lithium/sodium storage mechanisms,and it is necessary to investigate them in depth.In this paper,based on molybdenum-based,we combine them with carbon materials to explore their reaction mechanism deeply,improve their cycle stability during charge and discharge,and increase their sodium storage capacity.The following conclusions are obtained from the study of this paper.(1)Sodium molybdate was selected as the molybdenum source,manganese acetate as the manganese source,dopamine hydrochloride as the carbon source,and Tris solution as the solvent.The nanocauliflower like manganese molybdate/carbon composite(MnMoO4/C)was prepared by ultrasound-assisted stirring and calcination treatment.The unique nanocauliflower like structure is morphologically stable,rich in energy storage sites,and has high ion transport rate and conductivity efficiency.When used as the negative electrode of LIBs,it can reach 853 mAh g-1 after 100 cycles at 0.1A g-1,1500 cycles at 1A g-1,and 220 mAh g-1 after 100 cycles at 0.1 A g-1 and 5000 cycles at 1A g-1 when used as the negative electrode of SIBs.In addition,it maintains good cycling stability when assembled with sodium vanadium phosphate and lithium iron phosphate to form full cells,laying the foundation for its commercial application.(2)Molybdenum telluride/carbon nanoflower composites self-assembled by molybdenum telluride nanosheets were prepared by chelation,pre-oxidation and tellurization using ammonium molybdate as the molybdenum source,tellurium powder as the tellurium source,dopamine hydrochloride as the carbon source and ethanol/deionized water mixed solution as the solvent.It remained for 3000 cycles at a current density of 1Ag-1 and successfully assembled with Na3V2(PO4)3 to form a full cell,which is expected to have commercial applications in the future.(3)The molybdenum ditelluride/carbon composite film was successfully prepared by electrostatic spinning technology and tellurization,selecting acetylene-conjugated molybdenum as the molybdenum source,tellurium powder as the tellurium source and polyacrylonitrile as the carbon source.The film has advantage of excellent flexibility and can be used as an electrode material without the addition of any conductive agent or bonding agent.In addition,the onedimensional conductive path and three-dimensional fiber network can not only shorten the ion diffusion path and improve the electron conducting efficiency,but also stabilize the structure and greatly improve its cycling stability without significant decay for 5000 cycles at 1 A g-1.The MoTe2/C film can be regarded as a flexible anode material for sodium ion batteries with promising applications. |
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