Preparation And Electrochemical Properties Of Porous Organic Polymers-derived Cathode Materials In Lithium Sulfur Batteries

In the next generation of high energy density lithium secondary battery systems,lithium sulfur batteries have attracted widespread attention due to their low cost,abundant reserves,and extremely high theoretical specific capacity and energy density.However,the commercial application of lithium sulfur batteries have been hindered by several obstacles,such as low utilization of active materials,short cycling life,low energy density and low saf-ety.In this dissertation,focusing on solving these problems,we have selected key component of lithium sulfur batteries——cathode material as the research object,and investigated the preparation and modification of sulfur-containing cathode composites as well as the optimium of the preparation process of the electrode pieces.On the one hand,in order to achieve high sulfur utilization and excellent cycling stability,one type of new nitrogen-doped porous carbon cathode composites derived from main-chain imidazolium-based ionic polymers have been prepared,the polymer composites could serve as carbon precursors.An interlinked three dimensional conductive network was formed through close coverage and seamless junction of carbon nanotube by nitrogen doped porous carbon,and the shuttle effect of polysulfide is effectively suppressed during charge/discharge,this study has opened up new ideas for the development of high-performance lithium sulfur batteries;On the other hand,in order to construct high energy density lithium sulfur batteries,porous covalent organic gel polymers have been utilized for the first time in free-standing flexible high-sulfur loading composite cathodes,one type of new flexible cathodes with ultrahigh areal capacity have been developed,this study has provided a simple and feasible method for the preparation of flexible lithium sulfur batteries with high energy density.