Research On The Electrochemical Sodium Storage Performance Of Hard Carbon Anode Based On The Recovery Of Waste Cigarette Butts And Donkey-hide Gelatin Waste Medicine

Considering that there are abundant and low cost sodium salts on the earth's crust,sodium ion battery?SIB?is considered to be the most promising large-scale energy storage system due to similar physicochemical properties between Li and Na.Hard carbon material is recognized as one of the promising anode active materials for SIB due to large interlayer spacing,high specific capacity,high conductivity,stable properties and low cost.Compared with the method of synthesizing hard carbon material from chemical reagent,the obtaining hard carbon from carbon-containing waste can not only reduce the cost,but also help to save resources and protect the environment.For this reason,two kinds of carbon-containing wastes including waste cigarette butts and expired donkey-hide gelatin medicine were selected to obtain N-doped hard carbon micro-particles and N/S co-doped hollow hard carbon nano-spheres,respectively.The main contents of this work are listed as follows:?1?Hard carbon materials were prepared by pyrolysis and carbonization of waste cigarette butts at 700 and 800°C,respectively.The effects of pyrolysis temperature on the structure and electrochemical performances of hard carbon anode materials for Na-storage were investigated.The results showed that the surface morphology and particle size of N-doped hard carbon microparticles?NWHC?from waste cigarette butts were basically same at different pyrolysis temperatures,while their microstructures and electrochemical Na-storage properties were different.For example,NWHC carbonized at 700°C?NWHC-700?possessed lower degree of graphitization,higher content of N element and larger interlayer spacing than NWHC at 800°C?NWHC-800?.Moreover,under the same current density,NWHC-700 also exhibited high discharge capacity,good cyclic performance and rate performance.More disordered micro-structure,larger interlayer spacing and higher content of N element of NWHC-700 anode may be jointly responsible for higher electrochemical Na-storage performances.?2?The expired donkey-hide gelatin medicine as a carbon source was tried to be recovered in the form of N/S co-doped hollow carbon nano-spheres?NS-HHCNs?via a template method,and subsequent pyrolysis and template etching.The results showed that NS-HHCNs exhibited hollow nano-sphere structure,and N/S elements were successfully doped into the carbon sphere structure.Furthermore,NS-HHCNs anode delivered an initial discharge capacity of 661.5 mAh·g^-1 and a reversible discharge capacity of 174.3 mAh·g^-1 even at 2.0 A·g^-1 for 1000 cycles,indicating superior electrochemical Na-storage performances.The synergistic effect of N/S co-doped contributed to increase the interlayer spacing,electrical conductivity and Na-storage active sites,thereby improving the electrochemical performances.In addition,the existence of hollow structure was beneficial to alleviate the mechanical stress generated during the Na⁺deinsertion/insertion and increase electrode/electrolyte contact area,thus greatly promoting the rapid diffusion and transmission of Na⁺.