Preparation Of Transition Metal Sulfide/carbon Nanocomposites And Performance Study Of Lithium/sodium Ion Batteries

As an efficient and convenient electrical energy storage device,lithium ion batteries(LIBs)have been widely concerned in various fields of society due to their advantages such as high energy density,long cycle life,and environmental friendly.However,metal Li resources are very limited,unevenly distributed and expensive,which limits the further development of LIBs large-scale energy storage.Metal Na is located in the same main group of elements with Li,and has similar physical and chemical properties as Li and abundant resources on the earth.Therefore,sodium ion batteries(SIBs)have gradually attracted the interest of researchers.At present,commercial graphite carbon has the disadvantages of low specific capacity as the a anode of LIBs,which cannot meet the urgent needs of today's society for clean,environmentally friendly,convenient and efficient new energy sources.Therefore,it is essential to develop LIBs/SIBs anode materials with excellent performance.As a new type of anode material,transition metal sulfide has the advantages of high theoretical specific capacity and good electrical conductivity,so it has a great development prospects.In this paper,a series of transition metal sulfide/carbon nanocomposites were successfully prepared and characterized in terms of composition,structure and morphology,etc.;Then these nanocomposites were used as an anode to assemble into LIBs/SIBs to study their lithium/sodium storage performance.The main research contents of this article are as follows:1.Oxygen-incorporated sulfur defect WS2 nanosheets and conductive carbon carrier N,S co-doped graphene were hybrided to prepare oxygen-incorporated sulfur defect WS2/N,S co-doped graphene(O-DS-WS2/NSG)nanocomposites,and proved that the synergistic effect of composition,structure and doping defects,leading to the dramatically enhanced lithium storage performance of the active material.This unique structure not only increases the lithium storage active sites in the electrochemical process,enhances the kinetics of ion/electron transport,but also eases the volume expansion effect during charge and discharge.In addition,the combination of surface defects and heteroatom incorporation can effectively regulate the electronic structure,improve the intrinsic conductivity of the material and provide more active sites.Based on the synergistic effect of composition,structure and doping defects,when O-DS-WS2/NSG nanocomposites is used as a anode material for LIBs,it showed a higher specific capacity,excellent rate performance and outstanding cycle stability.Importantly,the reversible specific capacity can still be maintained at 721.2 mAh g-1 at a current density of 0.5 A g-1 after 300 cycles.2.sing aniline,NH4HB4O7·3H2O,and C3H7NO2S as N,B,and S source,N,B,and S-tri-doped graphene(NBSG)was successfully synthesized by a simple one-step calcination method.When NBSG was used as a an anode material for lithium/sodium ion batteries,it present high specific capacity,excellent rate performance and stable cycle performance.For example,the initial discharge/charge specific capacities of NBSG for LIBs can reach 1715.6 mAh g-1 and 1068.3 mAh g-1,respectively.After 100 cycles,the reversible specific capacity remains at 922.4 mAh g-1,and the loss of reversible specific capacity is only 12%;the reversible capacity for SIBs can be maintained at 403.6 mAh g-1at a current density of 0.1 A g-1 after 100 cycles.The excellent electrochemical lithium/sodium storage properties are mainly due to the introduction of heteroatoms and the synergy between the doped atoms:enhancing the conductivity of the material,increasing the interlayer spacing of the material and the generating carbon defects provide more storage sites/adsorption sites/active sites for lithium/sodium storage.3.he h-Co(OH)2-MOF-74 precursor was obtained by a hydrothermal method,and then the precursor is accepted a phosphorus/sulfurization using the mixture of P and S powder to obtain hollow porous Co9S8/CoP/C(h-Co9S8/CoP/C)nanocomposites in Ar atmosphere.XRD,Raman,SEM,TEM and XPS characterization were performed to determine the composition and structure of the nanocomposites.The obtained h-Co9S8CoP/C as a anode was assembled into a SIB for electrochemical performances testing.The measurement results shows that the h-Co9S8/CoP/C anode has a great sodium storage performance sofextremely high specific capacity,excellent rate performance(The reversible specific capacity of the h-Co9S8/CoP/C can reach 557.2 and 156.3 mAh g-1 at a current density of 0.1 and 1.6 A g-1,respectively)and good cycle stability.The outstanding electrochemical sodium storage behavior of h-Co9S8/CoP/C is mainly attributed to its unique structure and composition.The hollow structure can not only provide more space to relieve the volume effect caused by the repeated insertion and extraction of sodium ions,but also shorten the ion/charge diffusion path and accelerate the reaction kinetics.