Study On The Performance Of The Li-O₂ Batteries Controlled By Tellurides

Recently with the increasing energy shortage and environmental pollution problems,people’s demand for secondary clean energy is increasing,and the requirements for energy storage and conversion technology are becoming higher and higher,too.Among contemporary new energy storage devices,Li-O2 batteries have extremely high theoretical energy density,which is ten times of the traditional lithium-ion batteries,and can be comparable to fossil fuels,which has attracted widespread attention.However,Li-O2 batteries also have many disadvantages,such as the actual specific capacity is lower than the theoretical value,the polarization phenomenon is serious,the energy conversion efficiency is low,and the cycle stability is poor.Efficient cathode catalyst materials are an excellent way to ameliorate the performance of Li-O2 batteries.At present,researchers have studied various catalyst materials,but tellurides are still a blank in the direction of Li-O2 batteries cathode catalyst materials,which belong to transition metals chalcogenide compounds.Sulfides and selenides of chalcogenide compounds have been shown to have high catalytic activity.The focus of this paper is to explore the Li-O2 batteries performance of tellurides materials and explore its related catalytic mechanism.As a typical narrow band gap semiconductor material,SnTe material has excellent properties which other semiconductors do not have.It has broad application prospects in the field of catalysis.In addition,there have been corresponding studies in the direction of lithium-ion batteries and sodium-ion batteries.Therefore,SnTe materials are used as the stepping stone of the tellurides to the catalytic direction of Li-O2 batteries is feasible.The first part of this thesis mainly explores the catalysis of SnTe materials on the performance of Li-O2 batteries.First,DFT theoretical calculations prove that SnTe has crystal surface selectivity and synergistic catalytic properties,and(100)and(110)crystal surfaces have OER and ORR catalytic activities.SnTe particles were prepared by a simple hydrothermal method,and the materials were characterized by SEM,XRD,XPS and other means.Then a series of batteries performance tests were carried out to verify its catalytic activity and explore its catalytic mechanism.The experimental results show that the SnTe electrode has a higher charge-discharge specific capacity,high coulombic efficiency,and low overpotential.When at the current of 200 mA g-1with the limited specific capacity of 600 mAh g-1,it shows a cycle life of 140 cycles,and when the cut-off capacity is 1000 mAh g-1,it shows a cycle life of 100 cycles,and the cycle stability is high.Through the analysis of the production and decomposition of Li2O2 during charging and discharging,the valence of ions in SnTe materials,and other aspects,the catalytic mechanism was explored,which proved its ideal surface effect and excellent catalytic ability.The proof of the high catalytic activity of SnTe material fills the gap of tellurides in the direction of lithium oxygen batteries catalysis,and provides an effective new idea for the future exploration of Li-O2 batteries cathode materials.Taking into account the influence of morphology and size on the catalytic effect,the next part of this paper explores the catalysis of Ag2Te nanowires on the performance of Li-O2 batteries.The Ag2Te nanowires are also prepared by a covenient hydrothermal method.The space structure formed between the nanowires can effectively contain the charge and discharge products and carry out the material transmission,which greatly improves the catalytic effect of the batteries.The results of the tests show that the Ag2Te electrode exhibits high cycle stability with large currents.When the current density is 500 mA g-1,the limited psecific capacity is 1000 mAh g-1,it shows a cycle life of 270 cycles,and also shows a cycle life of 200 cycles at the current of 1000 mA g-1,with the limited specific capacity of 1000 mAh g-1.And through the corresponding characterization to reveal its catalytic mechanism,to provide a reference for the future exploration of tellurides-catalyzed lithium oxygen batteries.