Controllable Synthesis And Electrochemical Performance Of MoS₂ As Anode For Lithium-ion Batteries

With the worsening of environment,the development and application of new energy is urgent.In recent years,the rapid development of mobile electronic devices and electric vehicles has made the demand for lithium-ion batteries continue to grow.Lithium-ion batteries have many advantages,such as high energy density,good cycle stability and high safety,which make them the best choice for energy storage devices.With the increasing demand for the comprehensive performance of lithium-ion batteries,their current performance is increasingly unable to meet people's needs.Among them,the anode material is one of the focus of attention.At present,the commercial lithium-ion battery anode material is mainly carbon anode material.Its specific capacity is pretty low and the theoretical specific capacity is only 372 mAh·g^-1,there is little room for improvement.Therefore,it is urgent to find alternative lithium-ion battery anode material with higher capacity,longer cycle life and higher safety.A series of different anode materials for lithium-ion batteries have been extensively studied.Because of their unique crystal structure,two-dimensional nanostructured materials including graphene have attracted much attention.In two-dimensional nanomaterials,transition metal dichalcogenide such as MX₂?M=Mo,Ti,V and W,X=S or Se?have been extensively studied due to their unique structures.A common feature of these materials is that foreign atoms or alkali metals can be embedded in their interlayers.Atoms within the layer of these compounds are bounded by strong covalent bonds,while the adjacent layers are bounded by weak van der Waals force,forming a graphene-like structure.This unique structural feature promotes the embedding and removal of different cations,and makes them exhibit excellent electrochemical performance in lithium-ion batteries.Among these compounds,MoS₂ has attracted much attention due to its high specific capacity.However,the layered stacking structure of MoS₂ is prone to volume change during cycling,which affects its electrochemical performance.MoS₂ is a semiconductor material with poor conductivity,which can easily cause high impedance in lithium-ion batteries.At present,the main method to improve the capacity and cycle stability of MoS₂ is to expand the interlayer spacing to relax the stress generated during cycling and to reduce the barrier of lithium ion intercalation.MoS₂ nanoparticles were synthesized by sulfurization with the Mo precursor synthesized by DC arc-discharge method.By physical characterization,it was found that the interlayer spacing was significantly expanded than that of bulk MoS₂material?0.614 nm?,reaching 0.702 nm.Mo prepared by DC arc-discharge method have a diameter of 10²5 nm,uniform distribution and smaller particle size.As a precursor,the size of the product MoS₂ is limited and uniform distribution.Because Mo nanoparticles with a diameter of 10²5 nm are used as precursor,the size of the MoS₂ nanoplates obtained by sulfurization reaction is smaller,formed 5²0?m aggregates.The surface area reaches 80.42m²·g^-1,which greatly increased the contact area between active substance and electrolyte,reduced the stress generated during cycling and relieved the volume expansion,avoiding the rapid capacity fade caused by the pulverization of active substance.MoS₂ nanaoplates as anode materials for lithium-ion batteries exhibit relative high capacity and excellent cyclic stability,the reversible capacity of above 860 mAh·g^-1 is maintained during the first 100cycles.Atomic-scale Mo contributes increasing capacity during cycling and 2065 mAh·g^-1discharge capacity is obtained of its maximum intercalation of Li.