Study Of The Preparation And Electrochemical Performance Of Molybdenum Trioxide Based Flexible Cathode Materials For Lithium Sulfur Battery

In recent years,with the rapid development of flexible and wearable electronic devices,the research of flexibility and high energy density lithium sulfur（Li-S）battery has attracted great attention.However,the commercial application of flexible Li-S battery still faces many challenges.Among them,the unbending and shuttle effect of the flexible framework are the most important reasons that limit the commercial application of flexible Li-S batteries.Therefore,it is particularly urgent to develop a flexible cathode material for Li-S battery with sustainable bending and significant inhibition of shuttle effect.This paper selects conductive molybdenum trioxide（MoO₃）nanobelts as the flexible framework.As a transition metal oxide,molybdenum trioxide has a strong adsorption effect on long-chain polysulfides and can significantly inhibit the shuttle effect.The main research contents of this paper are as follows:（1）Pure MoO₃ nanobelts was synthesized by hydrothermal method,and then hydroiodic acid（HI）was used as reducing agent and intercalating agent to obtain ultralong conductive MoO₃ nanobelts.The 3D nanobelts structure can not only shorten the electron and ion transport paths,but also store electrolyte and long chain polysulfide,and physically absorb polysulfides.Especially,as transition metal oxides,MoO₃nanobelts have strong polar adsorption for polysulfides,which can inhibit the shuttle effect.When the current density is0.1 C,the initial specific discharge capacity of MoO₃/S composite cathode was 1337.2 m Ah g^-1,which still retained a specific discharge capacity of 610 m Ah g^-1 after 200 cycles.It was proved that MoO₃ paper has great advantages as the flexible carrier of Li-S battery.（2）In order to further suppress the shuttle effect and improve the cycle life of the battery,molybdenum disulfide（Mo S₂）was added as an electrocatalyst in this chapter.Mo S₂ not only accelerates the conversion rate of soluble polysulfides to insoluble Li₂S₂/Li₂S,and greatly prevents the diffusion of long-chain polysulfides,but also has stronger polar adsorption on long-chain polysulfides,and synergistically inhibits the shuttle effect with MoO₃.When the mass ratio of MoO₃ to Mo S₂ was 8:2,the cyclic specific capacity of the composite material was the highest.At the current density of 1.0 C,the specific capacity of the composite cathode was 695 m Ah g^-1 after 500 cycles,which indicated that MoO₃@Mo S₂ has a very stable cycling performance as a sulfur carrier in flexible Li-S batteries.（3）In order to batter improve the conductivity and structural stability of sulfur carriers,reduced graphene oxide（r GO）was added as the conductive network in this chapter,while MoO₃ nanobelts was used as the flexible framework and Sn O₂ was used as the electrocatalyst.When the current density is 0.1 C,after 200 cycles,the specific capacity of MoO₃@Sn O₂/S composite cathode was only 658.8 m Ah g^-1,while the specific capacity of MoO₃@Sn O₂@r GO/S composite cathode was 870.4 m Ah g^-1.By comparison,the specific capacity of the MoO₃@Sn O₂@r GO/S composite cathode is significantly improved,which is due to the coating and conductive network of r GO.