Molybdenum-Based Nanomaterials: Synthesis And Application In Lithium-Ion Batteries

Due to its high energy density,lithium ion battery is widely applied to portable electronic products?mobile phones or watches?,electric vehicles and so on.Graphite has low working voltage,low cost and good conductivity,it is currently the most widely used and one of the first commercial lithium-ion battery anode materials.However,the characteristic structure of graphite itself makes it easy to generate LiC6,while limiting the every six carbon atoms only allow to insert one lithium ion,leading to a low theoretical specific capacity of 372 mAh g^-1,far cannot satisfy the current business requirements.Nowadays,with the social demand of lithium ion battery with higher capacity,lighter weight and thinner volume,scientific researchers are studying better and more advanced batteries technology.To achieve it,we must choose the appropriate electrode materials to increase battery capacity,cycle life and rate capability on the premise of security.To attain a higher storage-capacity anode,great efforts have been put into transition metal oxide nanomaterials and transition metal sulfide nanomaterials.As natural resources,they are abundant.When they were used as lithium-ion battery anode,they showed high specific capacity and have become a focus in the electrochemical aspect.In this paper,molybdenum oxide nanomaterials,MoO₂/RGO nanocomposites and MoS₂/C nanocomposites were prepared via two-phased solvothermal method or molten salt method.And then,the electrochemistry properties of as-obtained nanomaterials were studied.The details are as follows:?1?Molybdenum oxide nanomaterials with various morphologies synthesized by two-phased solvothermal method and its electrochemical properties.By altering the hydrothermal temperature,we achieved molybdenum oxide nanomaterials with different phases,morphologies and sizes.In addition,the electrochemical performance of the samples were also tested.The electrochemical tests showed that Mo-200 exhibited better cycling ability and rate behavior.The discharge capacity of the sample remained 485.3 mAh g^-1 after 50 cycles at the current density of 100 mA g-¹,which is much better than the another three samples.?2?MoO₂/RGO nanocomposites synthesized by two-phased solvothermal method and its electrochemical properties.To improve the structural integrity and specific capacity,we combined the sample monoclinic MoO₂?Mo-200?synthesized in the second chapter with reduced graphene oxide?RGO?.After a high-temperature hydrothermal reduction process,we get MoO₂/RGO nanocomposites.Electrochemical studies showed that,after adding a certain amount of RGO,MoO₂/RGO nanocomposites had a more superior electrochemical performance.The discharge capacity of the sample remained 765.1 mAh g^-1 after 50 cycles at the current density of 100 mA g-¹,which is much better than the pure MoO₂ samples.?3?Synthesis of MoS₂/C nanocomposites with potassium humate as carbon source and its electrochemical properties.By using cheaper xinjiang characteristic resources potassium humate as carbon source,we synthesised MoS₂/C nanocomposites directly via molten salt method,and the electrochemical performance of the samples was also tested.The electrochemical tests showed that MoS₂/C-700 exhibited better cycling ability and rate behavior.The discharge capacity of the sample remained 554.9 mAh g^-1 after 50 cycles at the current density of 100 mA g-¹,which is much better than the other two samples.