Preparation And Properties Of Organic Electrolytes For Lithium-oxygen Batteries

At present,with the development of science and technology,the development of new energy storage and conversion system has attracted extensive attention and research interests.Among the potential energy storage devices,lithium ion batteries have been widely used in various portable electronic devices and devices,due to their high specific energy and capacity.However,due to the low energy density of traditional lithium ion battery?100?200 Wh/kg?,which cannot meet the needs of practical application in the development of large energy-consuming equipments,such as plug-in hybrid electric vehicle?PHEV?and electric vehicles?EV?,the lithium air battery has gained more and more attention because of its high theoretical capacity?3860 mWh/g?and the theoretical specific energy?11400 Wh/g?.Lithium air batteries are thought to have the potential to replace gasoline as the energy of vehicles.Recently,researchers have done a lot of work to improve the performance of lithium air battery,but the rechargeable lithium air battery still has many challenges with a view to the practical application.For example,the reaction of the lithium metal as the anode and the organic electrolyte forms the by-products,the organic electrolyte is flammable and the stability of lithium oxygen battery is low,the solid electrolyte for lithium oxygen battery may effectively avoid these problems.The solid electrolyte has been successfully synthesized and characterized by X-ray powder diffraction analysis?XRD?,field emission scanning electron microscopy?FESEM?,Fourier transform infrared spectroscopy?FT-IR?and electrochemical measurements.The structure and properties of solid electrolyte and the electrochemical performance of lithium oxygen battery electrolyte has been studied systematically.In this thesis,sol-gel method was used to prepare LiTi₂?PO₄?₃?LTP?and Lii,4Al0.4Ti1.6?P04?3?LATP?at a low temperature.The research shows the crystal structure of doped LTP has no change,but the ionic conductivity of LATP is obviously increased compared with LTP.The solid electrolyte materials are ground and pressed,and form the solid electrolyte sheet by sintering at an appropriate temperature.After that the solid electrolytes are applied in lithium air batteries.In the full charge and discharge test,the LTP lithium air battery delivers a specific capacity of 5100 mAh g-1 electrode,but lithium oxygen battery using the Li_1.4Al_0.4Ti_1.6?PO₄?₃ as the solid electrolyte can perform a capacity of 7991.3 mAh g-1 electrode-The discharge plateau of the Li_1.4Al_0.4Ti_1.6?PO₄?₃ based lithium air battery are significantly higher than that of LiTi₂?PO₄?₃ based Li-air battery.Discharge/charge profiles of batteries conducted under limited capacity of 500 mAh g-1 electrode demonstrates that the discharge voltage plateau of batteries is at about 2.65 V.The LiTi₂?PO₄?₃ based lithium air battery can achieve 12 discharge/charge cycles at 500 mAh g-1 electrode,and by contrast,the Li_1.4Al_0.4Ti_1.6?PO₄?₃ based lithium air battery can achieve 18 cycles.The characterization of after-tested Lithium air batteries indicates that the doped solid electrolyte can effectively improve the electrochemical performance of lithium air battery...