Study On Modification Design And Properties Of MoS₂ Cathode Material For Aqueous Zinc-ion Batteries

Aqueous zinc-ion batteries（AZIBs）are a prospective electrochemical energy storage technology due to its low cost,high safety and environmental friendliness.Generally,AZIBs consist of cathode active material,anode zinc metal,aqueous electrolyte,and separator.Among them,cathode active material has a powerful effect on the electrochemical performance of batteries.However,most of the current active materials suffer from the slow diffusion effect of zinc ions and poor conductivity.Although two-dimensional（2D）molybdenum disulfide（MoS₂）is a promising active material,poor electronic conductivity and inactive plane still limit its further development in AZIBs.Rational construction of conductive network heterostructures is an effective strategy to solve these problems.Based on this,this thesis aims to improve the conductivity of MoS₂ and unlock its active base plane through appropriate structural design,so as to improve its electrochemical performance in AZIBs.In this study,two emerging 2D materials,Ti₃C₂T_x MXene and reduced graphene oxide（r GO）,serve as growth platforms for MoS₂,respectively.Two novel heterostructures are designed by growing MoS₂in-situ and firmly coupling it on two excellent substrates.The main research and innovation results are as follows.A charge-discharge network of 1T-MoS₂/Ti₃C₂ MXene heterostructure is constructed by in-situ growth of MoS₂ on Ti₃C₂ MXene through hydrothermal method.1T-MoS₂/Ti₃C₂ MXene has high conductivity,small size effect and good hydrophilicity.The novel 1T-MoS₂/Ti₃C₂ MXene has a high-rate performance of284.3 and 105.2 m Ah g^-1at 0.10 and 10.00 A g^-1,respectively.After 3000charge-discharge cycles,the capacity retention rate is 93.2%,showing good cycling stability.The excellent electrochemical performance is derived from the efficient synergistic effect of 1T-MoS₂ and Ti₃C₂ MXene in the heterostructure.Systematic ex-situ tests show that the energy storage mechanism of 1T-MoS₂/Ti₃C₂ MXene involves highly reversible interlayer insertion/extraction of zinc ions and reversible transition between the semiconductor phase（2H）and metallic phase（1T）of MoS₂during charge-discharge process.Furthermore,the wearable quasi-solid-state zinc ion battery constructed with 1T-MoS₂/Ti₃C₂ MXene also shows stable electrochemical performance under different bending conditions.A charge-discharge network of 1T-MoS₂/r GO heterostructure is constructed by in-situ growth of MoS₂ on r GO through solvothermal method.Density functional theory simulation and calculation prove that 1T-MoS₂/r GO has low zinc ion diffusion barrier and high electronic conductivity.The excellent synergistic effect of 1T-MoS₂and r GO promotes rapid transfer of electrons at heterogeneous interfaces.Sulfur vacancies in the heterostructure also provide more active sites for zinc ion adsorption and diffusion.Thus,the novel 1T-MoS₂/r GO exhibits a high specific capacity of303.1 and 102.7 m Ah g^-1at 0.20 and 20.00 A g^-1,respectively.Systematic ex-situ tests show that the energy storage mechanism of MoS₂is highly reversible interlayer insertion/extraction of zinc ions.Furthermore,the flexible quasi-solid-state zinc ion battery constructed with 1T-MoS₂/r GO also shows appreciable charge-discharge capacity at different deformation states and different temperatures.