Preparation Of Cobalt Sulfide Based Composite Materials And Their Supercapacitor Performances

As an energy storage device,supercapacitor holds several advantages and the electrochemical performances mainly depends on the properties of the electrode material.It has proved that transition metal sulfides owe higher conductivity than that of transition metal oxides,providing more electrochemical active sites and smooth charge-ion transport channel.If cobalt sulfide is combined with other substances,such as conductive polymers or carbon materials,the electrochemical performances can be well improved by regulating the structure and pore condition.In this subject,the preparation and electrochemical performance of cobalt sulfide based composite electrode materials were mainly studied.The main contents are as follows:（1）First,the hexagonal Co（OH）₂ nanosheets were prepared by refluxing.Then the hexagonal Co（OH）₂ wrapped by different amounts of PmPD was obtained by in-situ polymerization in ice-water bath.Finally,Co₉S₈/PmPD was achieved by calcination with the addition of sulfur powder.In this structure,the hexagonal Co₉S₈ was wrapped by flexible PmPD,the good package thickness can provide suitable channels for electronic transport and hexagon thin sheet is conducive to ion rapid diffusion.In addition,flexible PmPD can not only provided high electrical conductivity of the composites,but also plays a significant effect on strengthening the stability.The specific capacitance reaches 950.1 F g^-11 at the current density of 0.5 A g^-1;In two-electrode asymmetric device,the specific capacitance still remain87.9%after 6000 cycles,and the power density is 36 W h kg^-11 at the power density of 374.67W kg^-1.（2）CoNi₂S₄/rGO composites were prepared by a simple solvothermal method.In this structure,CoNi₂S₄ nanoparticles deposited on the graphene layers,which can improve ion channels for boosting the electrochemical properties.At 0.5 A g^-1,the specific capacitance is1621 F g^-1,and there is almost no capacitance loss after 2500 charge/discharge cycles.Moreover,when applied to asymmetric two electrodes,AC//CoNi₂S₄/rGO shows capacitance of 126.6 F g^-11 at 0.5 A g^-11 and after 5000 cycles the capacitance remained 87.4%.