Preparation Of FeS₂/biomass Carbon Composites And Their Lithium Storage Properties

In recent years,transition metal sulphides have received much attention due to their high theoretical capacity,high energy density and suitable discharge voltage.Among them,FeS₂ has become potential because of its high theoretical capacity(894 m A h g^-1)as well as its advantages of non-toxic and low cost.However,FeS₂ has the shortcomings of volume expansion and poor electrical conductivity in the lithium embedding/delithiation process.Biomass-derived carbon has been used in the electrode materials of lithium ion batteries and has shown good performance for its low cost and simple process,micro/nano multistage structure and rich in various organic functional groups.Therefore,FeS₂/biomass carbon composites were developed using biomass as the template and carbon source,with a view to increasing the capacity of the material and improving its cyclic stability as well as its multiplicative properties.In this thesis,FeS₂/C composites with different morphologies were prepared by a simple iron salt impregnation,high-temperature calcination and sulfidation process using scallion root,poplar branches and Lonicerae flos as biomass templates and carbon sources.The composites were also characterised by advanced physical characterisation techniques such as TG,XRD,FT-IR,SEM,TEM,XPS and Raman spectroscopy,and the effects of the concentration of iron salt impregnation,calcination temperature,the amount of sulfur and sulfuration temperature on the microstructure and lithium storage properties of the products were investigated.The results of the electrochemical performance tests showed that:The inner cavity ribbed FeS₂@S-C composites were prepared using scallion root as the biomass template and carbon source,and the capacity increased to 1100 m A h g^-1 after250 cycles at 0.1 A g^-1,and even at 1.0 A g^-1,a capacity of 449 m A h g^-1 was kept after cycling 1000 times;The tube-like FeS₂@S-C composites were prepared using poplar branches as the biomass template and carbon source,and a capacity of 1177 m A h g^-1after 200 cycles at 0.1 A g^-1 was kept.The discharge capacity increased to 474 m A h g^-1after 1500 cycles at 1.0 A g^-1;The sheet-like FeS₂@N/S-C composites were prepared using Lonicerae flos as the biomass template and carbon source,and a reversible capacity of 1259 m A h g^-1 after 100 cycles at 0.1 A g^-1 was kept.The discharge capacity increased to 505 m A h g^-1 after 1500 cycles at 1.0 A g^-1.