Preparation And Sodium Storage Performance Of Carbon Nanosheets Derived From Coal Tar Pitch

With the continuous consumption of traditional fossil fuels such as coal and oil,the energy crisis and environmental pollution are becoming more and more serious,so the development and utilization of clean energy need to be solved urgently.In order to integrate these intermittent renewable energies such as wind,solar and wave into the electrical grid,corresponding large-scale energy storages?EESs?are essential to guarantee their stable output.The traditional energy storage devices such as lithium ion battery are limited by the high price and low natural abundance of lithium,therefore,the development of new energy storage technology becomes the key for the efficient utilization of clean energy.Sodium ion battery has been paid much attention due to its abundant reserves on earth and low price.The difficulty of constructing the anode material for sodium ion battery is to enhance its structural stability and Na storage ability by controlling the structure composition and microstructure of the active material.In this work,coal tar pitch with extensive sources and high carbon yield was used as raw material.By precisely designing its microstructure,carbon layer spacing,pore structure and chemical composition,high-capacity and long-cycle carbon anode materials were obtained.Detailed research contents are as follows:The nitrogen doped porous carbon nanosheets?PCNS1000?were successfully prepared by heat treatment of coal tar pitch and NaCl template in NH₃/Ar atmosphere.PCNS1000possesses an expanded interlayer distance,appropriate mesoporous structure,high nitrogen content.Moreover,PCNS1000 retains soft carbon feature to a certain extent and consequent relative high conductivity.Benefiting from its appropriate structure and chemical composition,PCNS1000 exhibits a high reversible capacity of 270 mAh g^-1 at 100 m A g^-1 in sodium-ion half cells.After an ultralong charge-discharge cycling of 10000 times a charge capacity of144 mAh g^-1 can be delivered at 2 A g^-1,and high capacity retention of 86%was achieved.The nitrogen sulfur co-doping carbon nanosheets?NS-800?were successfully prepared by heat treatment of coal tar pitch,melamine and NaCl template under H₂S/Ar.In consequence of the nitrogen and sulfur doping,the expanded interlayer distance of carbon material is greatly beneficial for Na storage.NS-800 exhibits a high reversible capacity of 344mAh g^-1 at 0.1 A g^-1.The capacity retentions were 93%both at 1 A g^-1 and 2 A g^-1 after 1000cycles.