Gelatin-based Gel Polymer Electrolyte And Binder Preparation And Its Application In Lithium-ion Battery

Rechargeable lithium ion battery has gradually become most attractive energy storage devices because of its high efficiency,lightweight design and long-term cycle life among commercialized batteries.However,conventional lithium ion batteries normally use flammable nonaqueous carbonates liquid electrolytes,resulting in a serious safety issue in use.Environmental protection is an eternal topic in material design,and the liquid electrolyte,polyolefin separator and toxic binder solution used in lithium ion batteries will cause a lot of environmental and safety problems.Using natural polymer materials(such as cellulose,chitosan,etc.)to prepare polymer electrolyte can not only avoid the problem of liquid electrolyte leakage and improve the safety of the battery,but also improve the battery energy density and other electrochemical performance.Gelatin is a natural polymer material with abundant sources,which is low in price and environmentally friendly.The research of using gelatin as lithium battery gel polymer electrolyte and binder meets the requirements of environmental protection.This paper mainly studies the following three aspects:1.Preparation of modified gelatin gel polymer electrolyteIn this study,gelatin was chemically modified by methylpropionic anhydride(MA)with double bond to obtain methylacrylamide-based gelatin(GelMA).was d by ing GelMA and polyethylene glycol diacrylate(PEGDA)was crosslinked to prepare GelMA/PEGDA polymer film(LGP)with the help of photoinitiator Ir2959 and UV light.LGP polymer films were characterized by infrared spectroscopy(FTIR),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA).The electrochemical performance of the gel polymer electrolyte prepared by this method was tested.The electrolyte(LGP-2/3)had high ionic conductivity(3.10×10-3 S cm-1)and large lithium ion migration number(0.89),as well as a wide electrochemical stability window(5.64 V)and good interfacial compatibility.In the voltage range of 2.5?4.2 V,the polymer lithium battery has stable cycling performance at 0.2 C,0.5 C and 1 C.2.Preparation of crosslinked modified gelatin binderGelMA/PEGDA polymer solution has high viscosity and good film-forming performance,so in this study,GelMA/PEGDA polymer solution was used as a water-soluble binder of positive-lithium iron phosphate(LiFePO4)to investigate its performance.The crosslinked GelMA/PEGDA binder(GP)was prepared by in-situ UV curing.The properties of the GP binder under different content ratios of GelMA/PEGDA,such as electrolyte swelling property,thermal stability,battery circulability,and the changes in pole morphology before and after cycling,were discussed.Experimental data show that GP binder significantly improved the electrochemical performance of the battery and had a high reversible specific capacity.GP binder was able to maintain the integrity of the LiFePO4 electrode structure over 300 cycles.GP as a water-soluble crosslinking adhesive also has the advantages of easy-processing and environmental friendliness,which is safer,more environmentally friendly and cheaper than PVDF adhesives based on organic solvents.3.Preparation of cathode-gel polymer electrolyte integrated lithium batterythe positive support gel polymer electrolyte membrane was prepared in situ UV-curable in this study,the integration of polymer lithium battery(LiFePO4-(LGP-G)/Li)has more excellent battery performance including higher coulomb efficiency and smaller cell polarization,in comparison to the traditional polymer lithium ion battery(LiFePO4/LGP-G/Li)using a separate gel polymer electrolyte membrane.