Synthesis And Electrochemical Performance Of Molybdenum Disulfide Intercalation Compounds

Over the past decades,lithium ion batteries?LIBs?have been applied in portable electronic devices and electric vehicles due to their high energy density and long cycle life.However,the limited resources of lithium have led to a drastic increase in cost.Thus,a substitution for lithium is highly needed.Sodium,with similar physicochemical properties to lithium,is an abundant and cheap element.Therefore,sodium ion batteries?SIBs?represent potential alternatives for developing low-cost and large-scale energy storage devices and have drawn a worldwide attention.However,the ionic radius of sodium is larger than that of lithium,resulting in dramatic volume variation and fast capacity fading,which limits the commercialization of SIBs.In this article,we chose molybdenum disulfide?MoS₂?as the research objects,and synthesized two kinds of MoS₂ intercalation compounds.These products were characterized through the modern testing technologies,and used as the insertion anode materials for SIBs.The main results are as follows:?1?The pristine MoS₂ was prepared through a hydrothermal method,and the methyl-intercalated MoS₂?M-MoS₂?was prepared through a second solvothermal method in the methanol solution,while the aniline-intercalated MoS₂?A-MoS₂?was synthesized by changing the methanol solution with water and aniline.Moreover,the detailed structrure information of MoS₂ and its intercalation compounds was characterized by XRD,BET,SEM,and so forth.?2?We tested the performances of SIBs with these samples as the anode materials in the voltage range of 0.6-3 V.The results showed that the MoS₂intercalation compounds possessed better electrochemical performances.At the current density of 1 A/g,the prisitine MoS₂ only showed a specific capacity of 29mAh/g after 500 cycles,while the M-MoS₂ and A-MoS₂ showed specific capacities of 79 and 85 mAh/g,respectively.In the rate test perormances,the pristine MoS₂ only delivered a specific capacity of 17 mAh/g at the current density of 5 A/g,and the specific capacities for M-MoS₂ and A-MoS₂ were 69 and72 mAh/g,respectively.?3?The reasons for the enhanced electrochemical performances of MoS₂intercalation compounds are attributed to the higher specific area,and larger interlayer distance,which could facilitate the diffusion of sodium ions and enable the fast electrochemical reation,resulting in a pseudocapacitive sodium storage behavior.Moreover,the enlarged interlayer distance can inhibit the structure variation and improve the cycling stability of materials.