Lithium-ion Storage Of Transition Metal Sulfides And Oxides Via Different Nanostructure-enhancing Methods

Contemporary sustainable energies are being improved to contribute to the reduction of the carbon emission footprint following the Paris Climate Agreement.Lithium-ion batteries have a leading role in making the zero-emission task possible before 2050.Lamentably,the existent electrode materials cannot supply the high demand of power,energy,and stability of the alternative technologies.This research aims at developing smart-engineered nanomaterials to serve as electrodes for lithium-ion batteries and lithium-ion capacitors,which could be used for the next generation of electronic devices.More specifically,the material selection consists of the synthesis of nanomaterials based on transition metals because of their great potential as replacement of graphite and other intercalation materials due to their low cost,environmental safety,and high capacities（600-1100 mAhg-1）.But,regardless of these advantages and good results,their volume expansion,pulverization,high irreversible capacity,and low conductivity prevent them from working in real applications.To upgrade their core deficiencies,we have chosen two strategies,i.e.,1)Physical constraint:the manufacture of a core/shell type nanostructure with a carbon layer as the shell enclosing the Mn₃O₄ and MnS at the core,so that the conductivity and the mechanical stability are ameliorated.2)Structural adjustment design:the enhancement of the ionic and electronic conductivity of MoO3 by doping vanadium atoms and the improvement of ionic conductivity of MoS₂ by enlarging the interlayer via adsorption of sulfur atoms.To produce Mn₃O₄@C,we have employed a simple two-step method of plasma evaporation of the bulk manganese in a methane and argon ambient,and the annealing of the precursor in the air at different temperatures.The core/shell arrangement ensured the stability of the composite during long cycles tests by buffering the volume expansion of the inner material.Mn₃O₄@C high energy storage for lithium-ion battery granted outstanding capacity retention during the rate capability test and large energy density of 109 Whkg-1,when employed as anode material for the lithium-ion capacitor.In the case of MnS@C,the precursor synthesis followed the same procedure of the previous nanocomposite,and then the sulfurization reaction was performed at low temperatures.High capacity and rate capability were achieved when used as the anode material.This smartengineered structure proved to deliver an enhanced Li+exchange within the microstructure.Core material adjustment in size and phase after constant cycling could improve Li+ion storage properties by increasing the ionic and electronic conductivity with a high capacity of 890 mAhg1 after 500 cycles for lithium-ion battery and high energy density of 90 Whkg-1 as the lithiumion capacitor.V-doped MoO3 layered material was fabricated via one-pot plasma evaporation of Mo/V₂O₅ as the bulk phase precursor in an argon environment.According to Density functional theory（DFT）calculation,vanadium was successfully incorporated in the MoO3 crystalline structure,which increased the electronic and ionic conductivity of the nanocomposite.The lithium-ion storage performance of V-doped MoO3 was remarkable in half-cell with 1184 mAhg-1 and 231 Whkg-1 in a full-cell configuration with LiCoO2 as a cathode material.The nanostructure was intact after 400 cycles,demonstrating the advantages of our smart-designed nanostructure.The exceptionally high capacity,energy density,and rate capability corroborated the beneficial effects of vanadium doping in terms of lithium storage.MoS₂ was produced to be used as anode material for lithium-ion batteries,by the mean of a two-step process of plasma evaporation and thermal sulfurization in a horizontal furnace.DFT calculations indicated that the S atoms were responsible for the enlargement of the layers’dspacing.The interlayer-expanded nanosheets encouraged the delivery of high capacity and remarkable long cycling stability preserving intact the nanostructrure after hundreds of cycles.This kind of MoS₂ with a lengthened interlayer space demonstrated high ion and electronic conductivity throughout the electrochemical performance with an excellent capacity of 2000 mAhg-1 after 350 cycles and an impressive rate capability.