Preparation And Properties Of Composite Solid-state Electrolytes

Over the past decades,with the extensive use of electronic products,people's requirements for energy storage components are increasing.As one of the main electrochemical energy storage components,supercapacitors have the advantages of high power density and long cycle life.However,the problem of low energy density in practical application obstructs its use as independent energy storage components,and therefore are often combined with batteries to form mixed energy.As an important part of supercapacitor,the properties of electrolyte directly affect many performance indexes.The traditional liquid organic electrolyte has great safety risks,so the solid electrolyte is an inevitable trend to expand the application scenarios of supercapacitors.In this paper,polyvinyl alcohol(PVA)was used as the main component of the matrix,and the flexible hydrogel electrolyte and the quasi-solid electrolyte,which reduced liquid composition are prepared respectively by compound with Polyethylene glycol(PEG).Different electrolytes were assembled with activated carbon electrode to analyze the relationship between the electrolyte and the performance of the supercapacitor.The main work of this paper is as follows:1.PVA/PEG hydrogel electrolyte was prepared by using Glutaraldehyde(GA)as a cross-linking agent.When the composite ratio of PEG is 10 wt.%,the ionic conductivity of the electrolyte is the highest,which can reach 8.5×10^-2 S/cm.A simple supercapacitor was prepared by using hydrogels of different components as electrolyte and adhesive,and the preparation process of the supercapacitor was investigated.2.PVA/PEG quasi-solid electrolyte was prepared by using LiClO₄ as conductive salt.After soaking the dried electrolyte film in ionic liquid for a period of time,XRD and FTIR tests showed that the composition of electrolyte has changed,indicating that a small amount of ionic liquid infiltrated into the polymer matrix.When the PEG composite ratio was 5 wt.%,the ionic conductivity of the electrolyte was the highest,which could reach2.3×10^-3 S/cm.In this chapter,membrane and quasi-solid electrolyte were respectively were used for assembly a supercapacitor,and it was found that the use of a membrane had an impact on the performance of the supercapacitor,and the electrolyte with higher ionic conductivity could increase the specific capacitance of the prepared supercapacitor to a certain extent and improve the rate performance.3.Li_6.4La₃Zr_1.4TA_0.6O₁₂(LLZO)inorganic filler was introduced into PVA/PEG quasi-solid electrolyte to prepare organic-inorganic composite polymer electrolytes.The particle size of the LLZO is 5?m.The experiment found that the dopants with large particle size will deposit at the bottom of the polymer membrane during the drying process,and can promote the formation of micropores,which are approximately perpendicular to the bottom surface of the electrolyte,further promoting the infiltration of ionic liquid.When the volume ratio of LLZO doping is 10 vol.%,The ionic conductivity reached 6.06×10^-3 S/cm.In order to reduce the polymer deposition and reunion,using freeze drying method of preparation of porous PVA-LLZO film as a"barrier","barrier"can be found effectively improved the deposition of inorganic doping and reunion,but also lost perpendicular to the surface of microporous,ionic conductivity drops,close to the electrolyte for doping LLZO,which indicated that the vertical micropore structure at the bottom of the electrolyte is the main factor that promotes the increase of ionic conductivity.