| The theoretical energy density of Li-O2 batteries is much higher than that of lithium ion batteries which are widely used at present,and it is also the highest in the existing battery systems.Li-O2 batteries are considered to be the ideal power source for electric vehicles and may revolutionize the automobile industry,thus attracting researchers'attention around the world.So far,people have made some achievements in the research of Li-O2batteries,but there are still many difficulties to overcome before the practical application,such as the poor rate performance,short cycle life,low round-trip efficiency and so on.The use of cathode catalysts is considered to be one of the fastest and most effective methods to improve the discharge capacity and cycling performance of Li-O2 batteries.Since the discovery of graphene,two-dimensional layered transition metal sulfides with similar structures have played an important role in catalysis due to their excellent optical and electronic properties.SnS2,as an important member,is a naturally formed n-type narrow-band gap semiconductor?2.2-2.4eV?.In recent years,SnS2 has shown excellent performances in energy storage fields such as solar cells,gas sensors,photocatalysis,lithium ion batteries and fuel cells,but it has been neglected in Li-O2 batteries.In this thesis,the application potential of SnS2 as the O2 electrode catalyst of Li-O2 batteries was explored for the first time.Different kinds of SnS2 with different structures were synthesized through the hydrothermal method and solvothermal method.The plate-like SnS2 with unique lattice structure can effectively promote the ORR&OER process and significantly improve the discharge specific capacity(the discharge specific capacity is9600 mA g h-1 at 200 mA g-1)and cycle performance?50 cycles?of the Li-O2 battery.A SnS2-C composite material was also designed to further improve the cycling performance of the Li-O2 battery?87 cycles?through synergistic action of SnS2 and C. |
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