Preparation And Sodium Storage Properties Of Interlayer-expanded MoS₂

MoS₂ has been widely investigated as anode material for sodium-ion batteries because of its inherent advantages such as high theoretical specific capacity(670 m A h g^-1)and graphene-like structure.However,its inherent low electrical conductivity and severe volume expansion during cycling lead to the rapid decay of its capacity,making it difficult to achieve commercial applications.For this reason,improving the electrochemical performance of MoS₂ by seeking suitable modification methods has become a hot research topic.In this study,two synthetic routes are proposed to prepare interlayer-expanded MoS₂ nanomaterials to improve their electrochemical properties.The interlayer-expanded pure-phase MoS₂ nanoflowers were prepared by a hydrothermal method using Mo O₃ as the precursor.By adjusting the initial reactant species and temperature,the reactants were first transformed into 1T-MoS₂ and finally into 2H-MoS₂.2H-MoS₂ synthesized by this method inherits the structural characteristics of the intermediate 1T phase expanded interlayer distance and fewer layer,and the interlayer distance reached 0.68 nm.The expanded interlayer distance can give a greater advantage to the high specific capacity advantage of the material and also further alleviate the bulk effect during cycling;the few-layer structure can simplify the ion diffusion path,expand its surface area and enhance its rate performance.The results demonstrate that the synthesized MoS₂ not only exhibited high specific capacities of 535.3 m A h g^-1 and 313.5 m A h g^-1 at 0.1 A g^-1 and 5 A g^-1,but also maintained a specific capacity of 420 m A h g^-1 at 1 A g^-1 after 100 cycles.To improve the cycle performance of the above materials,MoS₂/C nanosheets were prepared by a one-step hydrothermal method using metal-organic frameworks as the precursor,and the process was safe,non-toxic and green.The prepared MoS₂/C nanosheets contained a slight carbon,which maintained excellent cycle performance with reduced carbon content compared with other carbon composite methods.The addition of carbon reduced the specific capacity of MoS₂,but its cycle performance was greatly improved,with a specific capacity of 496.4 m A h g^-1 and 363.4 m A h g^-1 after150 cycles at 0.1 and 1 A g^-1,and the cycling retention rate was almost 100%.