Preparation And Lithium Storage Performance Of Graphite-like Biomass Carbon/FeS₂ And Nitrogen-doped Carbon/FeS₂

FeS₂ has a specific lithium storage capacit y of 894 m Ah/g,which is higher than that of the cathode materials for commercial lit hium-ion batteries.In addit ion,the sources of FeS₂ are abundant,the price is low and environmental.However,the conductivit y of FeS₂ is poor,and the shuttle effect of Polysulfide-lit hium exists in the process of charge and discharge,r esult ing in the attenuation of capacit y.In view of the above problems,this paper has carried out research from the following two aspects:（1）the graphit ized biomass carbon/FeS ₂（Bio-GC/FeS₂）with the different graphit ization degree and pore structure wa s prepared by using grapefruit peel sponge tissue as precursor through ion penetration,high temperature carbonization and solid phase vulcanization;（2）Nitrogen-doped carbon/FeS₂ hollow spheres（H-FeS₂/CN）were obtained by spray pyrolysis and solid phase vulcanization.A variety of structural and electrochemical analysis methods were used to study the microstructure and chemical composit ion of the above materials,and they were used as anode and cathode materials for lit hium ion batteries.The electrochemi cal lit hium storage performance of these materials was evaluated under the voltage window of 0.01-3.0 V and 1.0-3.0 V,respectively,and the following conclusions were drawn:（1）In graphite-like Bio-GC/FeS₂,the carbonization temperature determines the microstructure and graphit ization degree.With the increase of carbonization temperature,the graphitization degree of biomass carbon increases.At 800℃,the graphit ization of biomass carbon is obvious,and t he BET specific surface area and pore volume reach the maximum.At 900℃,the graphitization degree increases,but at the same time,the pore closure also occurs,and the specific surface area and pore volume decrease.Under the voltage window of 0.01-3.0 V and 1.0-3.0 V,the materials obtained by carbonization at 800℃have the best electrochemical lithium storage performance.The material has A reversible specific capacit y of 522 m Ah/g at A voltage window of 0.01-3.0 V and A current densit y of 20 A/g（～22.5 C）.In the1.0-3.0 V voltage window,the specific capacit y of the material still maintains 400m Ah/g after 400 cycles.（2）When the content of citric acid in the precursor solution is 1.6 g,the nitrogen-doped carbon/FeS₂ material（CA1.6）obtained through spray pyrolysis and solid phase sulfurization has a hollow sphere structure.The diffusion distance o f lit hium ions is short,and the hollow sphere can buffer the volume change of FeS ₂,so CA1.6 has the best electrochemic al lit hium storage performance.It has A specific capacit y of 492.1 m Ah/g after 820 cycles at A current densit y of 0.5 A/g.The reversible specific capacit y of 349 m Ah/g can still be maintained at the current densit y of 5 A/g after 1070 cycles.