Nitrogen-Rich Carbon-Based Materials And Their Electrochemical Properties

With the increasing demand for efficient and economic energy storage,there is significant emphasis today on creating a sustainable energy future for humanity.Lithium-sulfur batteries are widely seen as a promising next-generation energy storage system owing to their ultrahigh energy density and environmental benignity,yet the low electrical conductivity of sulfur and the shuttle effect of dissolved polysulfide result in poor cycling performance.The introducing of nitrogen heteroatoms to separators/cathodes can suppress the shuttle effect.However,most of the reported nitrogen-doped carbon materials for Li-S batteries are mainly powdery materials with a low nitrogen content(less than 10 at.%).Thus,seeking for a material with a higher nitrogen concentrations may provide more active sites to restrain the diffusion of polysulfide.The research contents can divided into three parts.1.The a-MEGO@g-C3N4 composite with high nitrogen content(20.08 at.%)and specific surface area(1000 m2 g-1was synthesized.Experiments shows that different nitrogen level composite can be prepared by different calcination method.2.Synthesis the nitrogen-doped graphene films by CVD method.Introducing the CH4 and NH3 as the C source and N source respectively.As a result,the domain size of nitrogen-doped graphene can reach over 350 μm.Our finding provides experimental instance of nitrogen doped graphene and would promote the research and applications in Li-S battery and electronic devices field.3.we developed an a-MEGO@g-C3N4 composite coated on polypropylene separator to inhibit polysulfide shuttling.The prepared lithium-sulfur battery with the a-MEGO@g-C3N4 coated separator delivered a specific capacity of 1244 mA h g-1at 0.1 C and a capacity decay rate of 0.062%per cycle after 800 charge/discharge cycles at 0.5 C,which are both superior to the battery assembled with standard separator.Further experimental studies indicate that the improved electrochemical performance is attributed to the superior surface area and nitrogen content which immobilize the polysulfides and reuse the trapped active material.