The Influence Of Manganese Oxide-graphene And Manganese Carbonate/graphene Coating On The Performance Of Lithium-sulfur Batteries

At present,more and more attention is attracted on the research about lithium-sulfur?Li-S?batteries,due to kinds of advantages about Li-S battery,such as the high specific capacity,environmental friendliness.However,the poor conductivity of elemental sulfur,"shuttle effect",volume expansion,lithium dendrite and other problems,result in low utilization rate of battery active materials,poor cycle performance to limit wide application of Li-S battery.It is effective to coat a film on separator to improve utilization of elemental sulfur and control the shuttle effect of polysulfide.In this study,two coating materials of manganese dioxide-reduced graphene oxide mixture and manganese carbonate/reduced graphene oxide mixture are prepared and coated on a separator to assemble a battery.The effects of two coated membrane on the properties of Li-S battery are investigated in details.?1?Manganese dioxide-reduced graphene oxide mixture films:the manganese dioxide nanowire prepared by the hydrothermal method and the reduced graphene oxide prepared by the hydrothermal reduction method are mixed,and then a slurry of both materials is coated on the separator to assembly into a battery.The experiment results show that the manganese dioxide-reduced graphene oxide mixture coating material has the most excellent performance when the mass ratio of manganese dioxide/reduced graphite oxide is 7:1.At high rate of 1C,the first discharge specific capacity is 1381.7 mAh·g^-1,and the reversible discharge specific capacity is 1289 mAh·g^-1 after 400 cycles,the discharge specific capacity remains at 588.3 mAh·g^-1,capacity retention rate At 42.58%,the capacity decay rate per cycle is only 0.1359%.?2?Manganese carbonate/reduced graphene oxide composite:By hydrothermal reaction,manganese carbonate grow directly on the graphene oxide to obtain a manganese carbonate/reduced graphene oxide composite coating material,and then a slurry of this composite is coated on a separator and assembled into a lithium-sulfur battery.The analysis results show that the manganese carbonate/reduced graphene oxide composite coating material has the most excellent performance when the mass ratio of manganese dioxide/reduced graphite oxide is 6:4.At the high current density of 1C,the first discharge specific capacity is 1614.1 mAh·g^-1,the specific capacity is 809.3 mAh·g^-1 after 100 cycles,the capacity retention rate is 50.14%,and the capacity decay rate per cycle is only 0.4986%.