Preparation Of Nitrogen Doped Porous Carbon Materials And Application Of Composite NiMn LDH Materials In Supercapacitors

Supercapacitors are drawing much attention as promising energy storage devices owing to their long cycle life,high power density,high chemical stability and low maintenance cost.Electrode materials are important determinants of supercapacitor performance.Nowadays,porous carbon materials have been widely used as electrode material of supercapacitors because of their high surface area and good electrical conductivity.Different methods and carbon sources are used to prepare porous carbon materials,which possess various pore sizes and structures.Selecting appropriate preparation methods and carbon precursors bears importance in adjusting pore structure parameters and lowering cost of porous carbons.However,traditional carbon precursor materials are expensive and can cause serious impact on the environment,enormously hindering practical application of carbon-based materials in supercapacitors.?1?LS-NCs were prepared from a green,low-cost,abundant and sustainable biological resource,waste lotus stems,by subsequent KOH activation.High N-6 and N-5 contents in the porous carbon may improve conductivity.Nitrogen-doped porous carbon showed a maximum specific surface area of 1322 m² g^-1,extraordinary microporous structure and superior electrochemical performance.The as-prepared samples exhibited excellent supercapacitor properties with high specific capacitance of 360.5 F g^-1 at 0.5 A g^-1.The electrode displayed excellent stability with 96%capacitance retention after 5000 cycles,indicating the feasibility of utilising waste biomass to produce promising low-cost materials for high-performance commercial supercapacitors.These findings highlight the possible utilisation of waste biomass for other energy storage applications,such as Li-ion batteries and hydrogen storage.?2?We designed and fabricated a complex layered architecture which consisting of high quality Ni-Mn LDH nanosheets grown on a nitrogen-doped carbon foam skeleton?denoted as LNCF?.Considering that the design of this three-dimensional structure can provide a three-dimensional interconnection network for the transfer of electrons and ions,allowing effective charge exchange.So the LNCF-2 electrode greatly improve the capacitance(2128.3 F g^-1 at0.5 A g^-1),while maintaining excellent rate performance and long cyclic life(94.3%retention after 5000 cycles at 2 A g^-1).In addition,an ASCs is prepared by using LNCF-2 as a positive electrode and NCF as a negative electrode,which exhibits a high specific capacitance,reached 125.1 F g^-1 at 0.5 A g^-1.Furthermore,it also exhibited excellent cyclic stability with80.1%capacitance retention after 10000 cycles at a current density of 5 A g^-1.