Preparation And Electrochemical Properties Of Rare Earth Doped Molybdenum Disulfide/graphene Anode Materials

As a typical two-dimensional transition metal sulfide,molybdenum disulfide(MoS₂)not only has a reversible lithium storage capacity of 670 m Ah/g but also can undergo multi-electron electrochemical reactions,and is expected to become a negative electrode material for lithium-ion batteries.However,MoS₂ has the problems of poor intrinsic conductivity and lithiation volume expansion.Research shows that the element doping strategy can enhance the intrinsic conductivity of MoS₂;compounding with a large specific surface conductive agent can increase the extrinsic electronic conductivity of MoS₂,and at the same time can alleviate the volume expansion of MoS₂.At present,a variety of element doping or introduction of conductive agents have been used to improve the lithium storage performance of MoS₂,but the lithium storage cycle performance of the material is still insufficient.To solve this problem,this article uses rare earth element doping to adjust the band gap of MoS₂ to increase its intrinsic conductivity,and use flexible conductive graphene as a carrier to alleviate the volume expansion caused by the lithiation reaction,and further promote its electronic and conduction of ions,thereby synthesizing a high-performance MoS₂-based lithium battery anode material.In this paper,a new type of rare earth element-doped MoS₂/reduced graphene oxide(RE-MoS₂/rGO where RE=Y,La,Ce,Nd)composite material is synthesized in one step by hydrothermal method.Through the structural characterization and electrochemical performance study of the system,Explored its potential as a negative electrode material for lithium-ion batteries.Through the research of this article,the main conclusions are as follows:The results of XRD,Raman and XPS analysis show that the rare earth elements Y,La,Ce and Nd have replaced the Mo element in MoS₂.Through SEM and TEM observations,it is found that the nano-flower-like RE-MoS₂ is embedded in the three-dimensional corrugated rGO surface.At the same time,it is found in HRTEM observation that the RE-MoS₂ layer spacing is larger than the standard MoS₂ lattice spacing by 0.62 nm.The electrochemical performance of RE-MoS₂/rGO materials has improved to varying degrees compared with undoped materials.Under the condition of a current density of 0.2C,Y-MoS₂/rGO,La-MoS₂/rGO and Ce-MoS₂/rGO has a reversible specific capacity of823.7,1194.3 and 843.8 m Ah/g after 100 cycles of cycling,while Nd-MoS₂/rGO still has a reversible capacity of 1202.3 m Ah/g after 80 cycles of cycling;compared with the RE-MoS₂/rGO material after 80 cycles,the Nd doping system is the most excellent.At the same time,the electronic density of states is calculated for MoS₂ and RE-MoS₂.The calculation shows that rare earth element doping can effectively shorten the band gap of MoS₂,which provides a theoretical basis for RE-MoS₂/rGO material energy storage.In summary,the rare-earth element doping enlarges the MoS₂ lattice spacing and widens the Li⁺transmission path.At the same time,the doping also shortens the MoS₂ band gap and enhances the intrinsic conductivity of the material.This is the difference between RE-MoS₂/rGO materials.Excellent lithium storage performance provides a guarantee.