| In order to vigorously promote the development of green,high-efficiency and sustainable energy,it is significant that the choice of energy storage equipment to solve the problem of discontinuity and seasonality of its output.The all vanadium redox flow battery(VRFB)has the advantages of instant response to charge and discharge,high efficiency,long cycle life,safety,reliability,and low price,so it is a potential large-scale high-efficiency energy storage system.Proton exchange membrane is the core part of the battery,which directly affects the efficiency and life of the battery.Today,it is a research focus on the development of a non-fluorine proton exchange membrane with low cost,high ion selectivity and high cycle stability.In this paper,sulfonated polysulfone(SPSF),which is inexpensive and easy to synthesize,is selected as the research object.In order to reduce the permeability of vanadium ions and improve its performance in vanadium batteries,cage polysilsesquioxanes(POSS)containing different types of functional groups are selected as the filler,which is to explore the role of different content of POSS in the SPSF/POSS hybrid proton exchange membrane and the effect on the performance of the vanadium battery.The main research results are as follows:(1)A series of SPSF/POSS-NH2hybrid proton exchange membranes were prepared by blending sulfonated polysulfone(SPSF)with the degree of sulfonation(DS)of 62and aminopropyllsobutyl polyhedral oligomeric silsesquioxane(POSS-NH2).With different content of the POSS-NH2,proton conductivity,vanadium permeability,mechanical strength and the performance of vanadium redox flow battery are investigated in detailed.The results showed that the addition of POSS-NH2increases the thermal decomposition temperature and proton conductivity to a value of 10.55m S cm-1.When the content of POSS-NH2is 5 wt%,the S-P-5%hybrid membrane exhibited lower vanadium permeability of 5.47×10-9cm2min-1,and higher proton selectivity(1.930×106S min cm-3),better than Nafion115 membrane(1.23×105S min cm-3)and S-P-0%membrane(5.41×105S min cm-3).Compared with S-P-0%membrane,S-P-5%membrane showed the best battery efficiency.Its coulombic efficiency(CE)can be maintained at about 99.4%,which is higher than Nafion 115membrane(92.38%)and S-P-0%membrane(91.72%).Meanwhile,The voltage efficiency and energy efficiency have also been significantly improved.The battery efficiency is still stable after 300 cycles,and the self-discharge time is 117h,which is10 times than that of Nafion115 membrane.The introduction of POSS provides a new idea for the improvement of SPSF proton exchange membrane performance.(2)Firstly,Functionalized octaphenyl POSS(OPS)is prepared by direct sulfonation method.Then a series of SPSF/SPOSS/IL hybrid proton exchange membranes were prepared by blending SPSF with sulfonated octaphenyl POSS(SPOSS)and added ionic liquids(1-butyl-3-methylimidazole Boron fluoride).The effect of IL addition on the performance of SPSF/SPOSS/IL hybrid membranes was studied.Compared with pure SPSF membranes,SPSF/SPOSS/IL hybrid membranes have better thermal stability,hydrophilicity and chemical stability.The easy loss of IL makes the hybrid membranes mechanical properties,vanadium resistance and vanadium batteries efficiency all showed a trend that first increasing and then decreasing.When the IL addition was 20 wt%,the S/SP-IL-20 hybrid membrane showed excellent comprehensive performance.The vanadium ion permeability was decreased to2.08×10-9cm2min-1,and the coulombic efficiency could be kept stable at More than99.6%,far better than pure SPSF membrane(91.72%).At a current density of 40 m A cm-2,the battery can stably cycle for 300 times,and the self-discharge time can reach93.5 h.There is a better performance in vanadium batteries. |
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