Carboxylated Chitosan Gel Polymer Electrolyte Film And All-Solid-State Supercapacitors

In recent years,with the spread of portable/flexible wearable electronic devices,flexible energy storage devices have become a research hotspot.Among the flexible/all-solid-state supercapacitors and other energy storage devices,the traditional separator/electrolyte structure can not meet the requirements.Gel polymer electrolyte?GPE?is the first choice of flexible/all-solid supercapacitor electrolytes due to its advantages such as shape controllable,high ionic conductivity,no liquid leakage,a certain mechanical strength,flexible,safety and environmental.In view of this,many researchers have focused on the study of gel polymer electrolytes.In this paper,three different gel polymer electrolyte membranes are prepared based on carboxylated chitosan?CYCTS?.The structure and properties of carboxylated chitosan gel electrolyte membranes are characterized,and then assembled with activated carbon for all-solid-state supercapacitors.The electrochemical properties of all-solid-state supercapacitors are studied.The main content of this paper are as follows.?i?Hydrochloric acid crosslinked carboxylated chitosan gel electrolyte membrane?CCH?.The CCH membrane is prepared by solution casting and immersion method,and CYCTS is used as polymer matrix,while hydrochloric acid is used as both crosslinking agent and electrolyte.The results show that the molecular chains of CYCTS were crosslinked by ionic bond and covalent bond under HCl conditions.The CCH film has a high ionic conductivity of 8.69×10^-2 S/cm and potential window of all-solid-state supercapacitor based on CCH is 0-0.9 V.At the current density of 0.5A/g,the specific capacitance is up to 45.9 F/g,and the energy density is up to 5.2Wh/kg.?ii?Carboxylated chitosan grafted polyacrylamide gel electrolyte membrane?CYCTS-g-PAM?.Compared with acid and alkaline electrolytes,the neutral electrolyte supercapacitor can provide a wider working voltage,thus improving the energy density of the device.Using Li₂SO₄ as electrolyte,KPS as free radical initiator,AM as graft monomer unit,and N,N'-methylene biacrylamide?MBA?as cross-linking agent,CYCTS-g-PAM-Li₂SO₄ membrane is prepared by initiating free radical graft copolymerization.The effects of the amount of monomer ratio,initiator and crosslinking agent on the ionic conductivity and electrolyte uptake of the membrane are investigated.The results show that the mechanical properties of CYCTS-g-PAM-Li₂SO₄ membrane are further improved compared with CCH film,and the all-solid-state supercapacitor achieves a high energy density of 8.7 Wh/kg within 0-1.4 V.?iii?Carboxylated chitosan grafted polyacrylate sodium gel electrolyte membrane?CYCTS-g-PAAS?.CCH membrane dissolves in alkaline solution.If CYCTS-g-PAM is used as matrix,absorption of alkaline electrolyte will hydrolyze.In order to make gel electrolyte based on carboxylated chitosan suitable for alkaline solution,using KPS as initiator,AA as grafting unit,NaOH as neutralizing agent,MBA as crosslinking agent and KOH as electrolyte,CYCTS-g-PAAS-KOH membrane is prepared by radical graft copolymerization.The results show that all-solid-state supercapacitorbased onCYCTS-g-PAAS-KOH membrane hasexcellent electrochemical performance at 0-0.9 V.In this paper,the performance of three different gel electrolyte membranes?HCl,Li₂SO₄ and KOH as conductive materials?based on carboxylated chitosan for all-solid-state carbon-based supercapacitors is studied.The purpose of preparing gel polymer electrolyte membrane with carboxylated chitosan as polymer matrix and acid,neutral and alkaline as electrolytes is successfully achieved.As a new kind of gel polymer electrolyte material,hydrochloricacidcrosslinkedcarboxylatedchitosanandcarboxylated chitosan/polymer has potential application value in other energy storage devices.