Preparation Of Transition Metal Sulfur/oxide Composite Electrode Materials And Properties Of Supercapacitors

Irreversible exploitation of energy resources,massive industrialization,and technological innovations steering the global development have created a demand for highly efficient energy storage devices.Currently available energy storage devices mainly include batteries,fuel cells and supercapacitors on the market,among which battery devices have poor power density and cycle stability,while supercapacitors have excellent inherent security,rapid charge and discharge,higher power density and outstanding cycle capability characteristics,which have been regarded as a substitute for dielectric capacitors,they have great development potential in the field of high efficiency energy storage.There are many factors affecting the performance of supercapacitor,among which the performance of electrode materials play a key role.Among them,transition metal sulfides are often used as electrode materials for supercapacitors because of their excellent conductivity and high theoretical capacitance,but traditional transition metal sulfides generally have shortcomings such as large volume structure change,high production cost,slow particle diffusion and low capacity.Therefore,it is very important to explore new transition metal sulfides and their composites as electrode materials for supercapacitors.In this paper,a new type of FeS/C composite material was successfully prepared as the negative electrode material of supercapacitor,and different metal oxide/carbon composite materials and FeS/C composite material were used as the positive electrode materials and the negative electrode material to build complete supercapacitor systems respectively.The electrochemical properties of aqueous electrolyte（KOH）and solid electrolyte（PVA-KOH）were investigated.The specific research content can be divided into the following three parts:（1）Starch,as a natural product,is a high quality raw material for carbon preparation.FeS/C composite materials were prepared by starch dispersion precipitation method as negative electrode materials of supercapacitors.The optimal ratio of carbon powder and metal sulfide in the electrode composites were investigated through the micromorphology characterization and electrochemical performance test（cyclic voltammetry（CV））,and the FeS/C composites with the best electrochemical performance were successfully prepared.In addition,Using Ni（OH）2/C composite and FeS/C composite as the positive and negative electrodes of the supercapacitor to constructe an asymmetric capacitor system,and the electrochemical test of the supercapacitor was carried out.（2）Using starch carbonization as carbon source,V₂O₃/C composites were successfully synthesized by precipitation reaction between carbon powder and NH₄VO₃ solution,which tends to have a cross-linked structure with many openings.The morphology of V₂O₃/C composites and the electrochemical performance were tested.V₂O₃/C composite and FeS/C composite were used as positive and negative electrode materials of supercapacitor respectively.And the performance of the supercapacitor was tested.（3）Glucose can be used not only as a carbon source,but also as a dispersant..The MnO₂/C composites were synthesized by a simple and rapid method,and their morphologies were characterized,the MnO₂ microspheres were uniformly dispersed in the carbon materials.The electrochemical performance of the electrode materials was also tested.An asymmetric supercapacitor was constructed by using MnO2/C composite and FeS/C composite as positive and negative electrode materials respectively.At the same current density,the performance of the supercapacitor was tested in two different electrolytes(KOH aqueous electrolyte solution and gel electrolyte（PVA-KOH）.Among them,the gel electrolyte（PVA-KOH）can be used not only as electrolyte but also as diaphragm.Finally,their performance was compared.