| Due to the pollution caused by the burning of fossil fuel,the continuous increase in the level of greenhouse gases in the atmosphere cause the necessity of exploring renewable and environmentally compatible alternative energy sources such as photovoltaics,wind energy and geothermal.The storage and delivery of energy is crucial to maintain the development of these green resources.Electrochemical cells are the ideal system to meet this demand.Lithium-ion batteries have been used most frequently in the battery market since the industrial production in 1900,yielding the largest and irreplaceable batteries.In order to obtain lithium-ion batteries with higher performance,the optimization of electrode materials?used to increase energy density?and electrolytes?used to improve safety?is one of the directions.Among them,the polymer gel electrolyte?GPE?shows the unique appearance of plastics which has both good ionic conductivity and good mechanical properties,causing a research boom.Based on copolymers,the study of GPE was carried out In this paper.The contents and conclusions of the experiment are as follows:1)A pre-synthesized acryloyloxybenzophenone?MABP?containing a photosensitive crosslinking group is chosen as the crosslinking agentone and one of the monomers,with the co-polymer of MABP and N-N dimethyl acrylamide?DMAA?as a matrix material.The GPE that can be applied to LIB is successfully synthesize by casting a film with an ionic liquid and a corresponding lithium salt solution in combination with a ultraviolet?UV?light radiation cross-linking technique.FTIR,TG and DSC,electrochemical impedance spectroscopy?EIS?,linear sweep voltammetry?LSV?,interface impedance,and cell performances are applied to characterize the property of the synthesized materials.FTIR results show that the poly?DMAA-co-MABP?and crosslinked network structure of GPE is successfully synthesized.TG results show the electrolyte membrane has a higher decomposition temperature with different content of the cross-linked components.The decomposition temperature are higher than 300°C.When the molar content of crosslinking agent acryloyloxybenzophenone?MABP?is 30%,the ionic conductivity?of GPE at room temperature reaches 1.16×10-4S/cm.To measure its electrochemical performance,The gel polymer electrolyte membrane is assembled into a button cell.The electrochemical stability window reached 4.6 V,and the first discharge capacity of GPE is 125.2 mAh/g.2)The pre-synthesized copolymers containing photo-sensitive cross-linking groups?MABP and DMAA copolymerization?serving as matrix materials is cross-linked under UV light.After the liquid electrolyte was adsorbed,the electrolyte was activated to obtain a gel polymer electrolyte.The TG and DSC curves of the crosslinked network structure of GPE show the thermal stability of the electrolyte membrane after being soaked is not as low as that of the unsoaked electrolyte.When the molar content of the crosslinking agent MABP is 10%,the liquid absorption rate is 126.15%and the?at the room temperature is 1.17×10-4 S/cm.The GPE with a light irradiation crosslinking time for 1 h has the best room temperature ionic conductivity,and its value is up to 6.342×10-4 S/cm.Through the characterization of the LSV and interface impedance of GPE,it can be seen that the electrochemical stability window of the all GPE is above 4V,and the highest value is up to 5.0 V.At a constant current density of 0.2C,the specific charge capacities of the initial and the80th cycles of the battery based on GPE is 345.2 mAh/g and 109.8 mAh/g seperately,and the initial discharge specific capacity is 308.9 mAh/g,the efficiency is89.48%.After 100 cycles,the discharge specific capacity is 108.3 mAh/g and the efficiency is 98.66%.3)GPEs were prepared by the polymerization of POSS-MA and BVIM-Br under UV light irradiation.The different molar ratios?1:100,1:75,1:50,1:25?between POSS-MA and ionic liquid BVIM-TFSI is explored.The compound BVIM-Br and P?POSS-?BVIM-TFSI??is confirmed to be successfully synthesized by FTIR and 1H-NMR.When the molar ratio of POSS and monomer is 1:75,the electrolyte has better ionic conductivity.Its room temperature ionic conductivity reaches 1.468×10-55 S/cm and its ionic conductivity is 2.83×10-44 S/cm at high temperature. |
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