Study On The Performance Of YS₂ As Anode Material For Li/Na-Ion Battery

With the rapid development of economy,people’s demand for energy is increasing.Traditionally,most of the world’s energy needs have come from coal,oil and natural gas.But with the massive use of these fossil fuels,environmental pollution and energy shortages have become increasingly serious.Li-ion batteries(LIBs),as a kind of secondary batteries,have been gradually introduced to the public by virtue of their advantages of high specific energy,low self-discharge,long cycle life and environmental protection.Therefore,the development of new power batteries and efficient energy storage system has become the direction of our efforts.At present,LIBs has been found in every corner of our lives,ranging from portable electronic devices such as watches,mobile phones and laptops to energy storage systems such as hydropower,wind and solar power stations.It is mainly composed of positive electrode material,negative electrode material,diaphragm and electrolyte.The high performance electrode material not only improves the charging and discharging efficiency of the battery,but also improves the quality of people’s life.In this paper,we use the first principle calculation,based on density functional theory(DFT)and crystal structure prediction technology to propose a new two-dimensional(2D)single-layer LIBs anode material YS2,and study its performance as anode material for LIBs and Na-ion batteries(NIBs).We calculated the band structure and density of state(DOS),and found that YS2 had a metallic property,which was well maintained throughout the lithiation/sodiumation process.The results of phonon spectrum and ab initio molecular dynamics(AIMD)simulation show that YS2 is dynamically and thermally stable.The calculated adsorption energy of Li and Na on YS2 is-2.038 eV and-1.939 eV,respectively.The ultra-high adsorption energy ensures the stability of Li-/Na-YS2 system in the process of lithiation/sodiumation process,and the diffusion barrier is 0.33 eV and 0.24 eV,respectively.The ultra-low energy barrier shows that Li+/Na+can transfer rapidly between the positive and negative electrodes,improving the charge-discharge rate of the battery.The theoretical specific capacity of YS2 is 350 mA·h g-1,which is equivalent to that of graphite electrode.These characteristics show that the 2D YS2 monolayer can be useas a promising anode material for LIBs/NIBs.