Study On Controllable Preparation Of CoS_x-based Nanocomposites And The Performance Of Solid-state Hybrid Supercapacitors

In order to meet the demand for efficient energy storage devices in the modern electronics market,small,lightweight and flexible electronic products have attracted tremendous interest.Among energy storage systems,supercapacitors have attracted great attention due to their fast charge and discharge rates,excellent stability,high power density,low maintenance cost and safe operation.Supercapacitors have been widely applied in many fields,such as portal electronic equipment,backup power supplies and hybrid vehicles.However,the energy density of supercapacitors is significantly lower than batteries,which makes it unable to meet the growing energy demand,especially for the next generation of portable energy storage devices.Therefore,it is critical to further boost the energy density of the supercapacitors without compromising their power density,which cab be further improved by extending the cell potentials and enhancing the specific capacities.Based on the above consideration,this paper will focus on the synthesis and performance of CoS_x-based nanocomposites and discuss the preparation process of CoS_x-based nanocomposites and to improve their conductivity and energy density.It will be explained in the following three aspects:1.Construction of Co O/Co-Cu-S hierarchical tubular heterostructures for hybrid supercapacitors.In this work,we prepared porous CoO/Co-Cu-S HTHSs constructed from nanoneedles by a multi-step method.CoO/Co-Cu-S HTHSs show good electrochemical performance due to their unique structure and synergistic effects.This can be attributed to the following aspects:First,different components in CoO/Co-Cu-S HTHSs can introduce more electroactive sites,resulting in higher specific capacity.Secondly,rapid migration of electrons and charges can be achieved by forming heterogeneous interfaces.Third,hierarchical tubular heterostructures can shorten the charge/ion diffusion path and expand the interface contact between the electrolyte and the electrode material,thereby improving electrochemical kinetics,enhancing rate performance,and cycling stability.2.Construction of mesoporous Cu-doped Co₉S₈ rectangular nanotube arrays for high energy density all-solid-state hybrid supercapacitorsIn this work,we propose a simple template sacrificial method to successfully prepare Cu-Co₉S₈ NTAs,which combines the advantages of metal ion doping and hollow nanostructure arrays.Compared with the pure Co₉S₈ NTAs,Cu-Co₉S₈ NTAs exhibits better electrochemical performance.This is mainly due to the"dead volume"caused by Cu-Co₉S₈ NTAs without the addition of a polymer binder and conductive additives,and the doping of Cu ions can act as electron donors,which enhance the conductivity of the electrodes.In addition,MOF-derived hollow structures with rough surfaces provide more electrochemically active sites,ensure sufficient interfacial contact between the electrode and the electrolyte,and can accommodate volume expansion processes during cycling.3.Construction of Fe and Mn co-doped Co₃S₄ nanosheet arrays for hybrid supercapacitors.In this work,we have adopted simple hydrothermal and solvothermal methods to successfully prepare FM-Co₃S₄ ultrathin NSAs.Due to the co-doping of Fe and Mn ions,FM-Co₃S₄ ultrathin NSAs show better electrochemical performances than Co₃S₄ ultrathin NSAs.This is because the electrode materials directly grow on 3D porous nickel foam.It can effectively enhance the conductivity of the electrodes.The doped iron and manganese ions can increase the conductivity and provide more electrochemically active sites,thereby increasing the specific capacity and having good rate performance.In addition,the nanosheet arrays can fully contact with the electrolyte ions to facilitate the redox reaction.