Study On Preparation And Application Of Lignocellulose-based Gel Electrolyte

In the traditional energy storage device,the diaphragm material is not easily degradable,and the liquid electrolyte is easy to leak,so the development and utilization of gel polymer electrolytes are particularly important.Gel polymer electrolytes have the dual functions of diaphragm and liquid electrolyte,and have the characteristics of low cost,environmental protection and high safety.Cellulose could well.dissolve with the.form of macromolecules.chains in the alkali/urea solution under certain conditions.Thus,cellulose at the molecular.level could be.modified by physically.and chemically.to development of a variety.of cellulose-based materials.In this thesis,cellulose was used as raw material and N,N’-methylene bisacrylamide(MBA)as a crosslinking agent,cellulose membranes were prepared by chemical crosslinking method and solution casting method.And then the cellulose membranes absorbed liquid electrolytes to form gel polymer electrolytes,which were applied to lithium-ion batteries and all-solid-state supercapacitors,respectively.Firstly,cellulose membranes(CM)were prepared by solution casting method with cellulose as raw material and MBA as a crosslinking agent,the CM absorbed liquid electrolyte to form cellulose gel electrolyte(GCM).The influence of crosslinking agent content on the application of the GCM in lithium ion battery was investigated.The results show that the electrochemical performance of the GCM has a trend of first increasing and then decreasing with the increase of the crosslinking agent content.The GCM-3 with crosslinking agent content of 5 wt% has better electrochemical performance,and its ionic conductivity can reach 1.26 m S/cm.Secondly,under the condition of crosslinking agent of 5 wt%,the influence of polyethylene glycol addition amount on the application of polyethylene glycol/cellulose gel electrolytes(CPE)to lithium ion battery was studied.The results show that the ionic conductivity of CPE is significantly increased(2.03 m S/cm)by adding polyethylene glycol.After 50 cycles at 0.5 C rate,the specific discharge capacity of the battery assembled with CPE can reach 101.3 m Ah/g,and the capacity retention rate is 80.9%,showing good cycle stability.Finally,cellulose membranes CM-3 absorbed 6 mol/L KOH electrolyte to prepare gel polymer electrolyte,and the effect of absorption time on the performance of gel polymer electrolyte was studied.The results show that with the increase of absorption time,CM-3appears gelation,dissolution,and re-gelation phenomenon.And the surface morphology of CM-3 changes from a loose lamellar structure to a small and compact pore structure.When the gel electrolyte and activated carbon electrodes were assembled into an all-solid-state supercapacitors,the operating voltage window is widened and can reach 2 V,which significantly improves the energy density of the all-solid supercapacitor.The maximum energy density of 18.5 Wh/kg can be achieved at a power density of 500.0 W/kg.