Mesoporous Carbon Nanofibers Flexible Freestanding Electrode For Electrochemical Storage Energy

With the continuous progress of the society and the rapid development of science and technology,the rapid depletion of traditional fossil fuels and severe environmental pollution in the world have seriously hampered the sustainable development of society.Therefore,the exploitation of clean energy sources is one of the most effective ways to solve the above problems.However,most of the renewable clean energy sources are intermittent and volatility?such as wind power,tidal power and solar power?and cannot satisfy people's demands for casual usage.Those renewable clean energies are highly rely on the time and daily weather conditions,so the developing of advanced energy conversion and energy storage devices which can guarantee the continuity of power supply is of great importance.Based on these considerations,supercapacitors and lithium sulfur batteries are considered as most significant electrochemical energy storage/conversion devices.Supercapacitors have become a research hot topic in the field of energy storage because of their high power density,while lithium sulfur batteries?Li-S?have become the focus in the high energy density electrochemical energy storage system.Carbon materials are often used as electrode materials for supercapacitors and elemental sulfur conductive framework materials for lithium-sulfur batteries,due to its excellent electrical conductivity,high specific surface area,and low price.In this work,an in-situ nitrogen-doped carbon nanofibers?N-MCNFs?flexible self-supporting electrode material was successfully prepared by electrospinning method.We employed the material as an electrode for supercapacitor and performed electrochemical performance tests.What's more,we also used the material as a host of active material elemental sulfur to fabricate sulfur/carbon composites for cathode of Li-S batteries and performed the electrochemical performance tests.The contents of study are as follows:?1?A low-cost,one-step synthesis of magnesium hydroxide?Mg?OH?₂?deposited on polyacrylonitrile?PAN?nanofibers was carried out by electrospinning technique.After the carbonization and etching process,in-situ N-doped mesoporous carbon nanofibers?N-MCNFs?network was prepared.The synthesized nanofiber networks was employed as a flexible freestanding electrode for supercapacitors.The as-constructed supercapacitor based on the N-MCNFs prepared at 900°C?N-MCNFs-900?can deliver excellent performance with an ultrahigh specific capacitance of 327.3 F/g at a current density of 1.0 A/g,and remarkable cycling stability,e.g.,only about 7%loss after 10,000 cycles at a constant high charging-discharging current of 20.0 A/g in 6 M KOH aqueous electrolyte.?2?We prepared an in-situ nitrogen-doped mesoporous carbon nanofibers?N-MCNFs?matrix by electrospinning technology to synthesize a kind of sulfur cathode,which was used to mitigate the diffusion of lithium polysulfide.Sublimed sulfur was introduced into the mesoporous carbon nanofibers by an easy melt diffusion method to prepare flexible self-supporting S/N-MCNFs cathode materials.When S/N-MCNFs composite was used for sulfur cathode materials,Li-S batteries exhibit excellent electrochemical performance.In addition,the design of nanostructural electrode demonstrated to be robust composites films during the charge/discharge process for³00 cycles and enabled extraordinarily excellent electrochemical performance with a reversible capacity of 813 mA h/g at a current rate of 0.5 C,which benefits from the high electrical conductivity and the unique mesoporous structure that homogeneously distribute and immobilize sulfur in mesoporous structure.