Design And Synthesis Of VS₂ Nanomaterials And Its Application In Rechargeable Batteries

During the past two decades,lithium ion batteries（LIBs）have played an important role in portable electronic devices.Considering the high cost and limited energy density,beyond lithium ion batteries such as alkali metal ion（Li+,Na+ and K+ ions）batteries and lithium sulfur batteries have emerged as candidates for the large-scale energy storage system.The main research contents are listed as follows:（1）A facile solvothermal method is developed to prepare VS₂ nanosheet assemblies（VS₂ NSA）for the storage of different types of alkali metal ions（Li+,Na+,and K+ ions）.The use of NMP is found pivotal for controling the morphology of final products from the following aspects: it has a sufficiently high boiling,low viscosity,and suitable surface energy.Electrochemical measurements show that VS₂ NSA enable the rapid and durable storage of Na+ and K+ ions.We believed that such extraordinary performances are benefited from the structure and unique morphology of VS₂ NSA.Firstly,the open space between nanosheets within the hierarchical NSA allows for easy mass transport,and effectively buffer the volume change during repetitive cycling.In addition,the experimental results of this study are further supported by density functional theory（DFT）calculations showing that the layered structure of VS₂ has large adsorption energy and low diffusion barriers for the intercalation of alkali metal ions.（2）VS₂ ultrathin nanosheets（VS₂ NS）are developed by the similar method and can be used as a catalyst for high-performance lithium-sulfur batteries.Individual nanosheets with a uniform distribution are featured with a few atomic layer thickness.Electrochemical results indicate that the presence of VS₂ can lower the polarization,accelerate the redox reaction,and improve sulfur utilization.In addition,ex-situ experiments show that VS₂ additives are highly effective as polysulfide immobilizers in lithium-sulfur batteries.We believe that the extraordinary preformance of batteries maninly contribute to the catalytic effect and chemical anchoring of VS₂ NS.