Preparation And Charaction Of Speek Membranes For Fe/cr Mixed Electrolyte Redox Flow Battery Application

Redox flow battery is a new storage battery, with some advantages, such as a brisk start speed, large storage capacity, high energy efficiency, safety and reliability, ion exchange membrane and electrode are key components of the battery. Currently, all-vanadium electrolyte have the great widely studied, but expensive, serious corrosion, and V5+oxidation limits the all-vanadium redox flow battery applications. Iron and chromium have cheap prices and iron-chromium mixed electrolyte avoids cross-contamination during battery charging and discharging process. The electrolyte can be recycled avoiding resource waste and environmental pollute.Ion-exchange membrane is another key component of flow battery, although commercial Nafion membranes possess high proton conductivity, good chemical stability, but their shortcomings are obvious, such as soaring prices, serious active ion penetration, small ion selective and so on. Sulfonated polyether ether ketone (SPEEK) is non-fluorinated proton conducting membrane with a good performance which can be used in flow battery. Nanofiltration membrane is also a good choice, selecting a membrane pore diameter larger between the H+and reactive ion. Battery realizes circuit because of H+through the membrane.In this thesis, the cyclic voltammograms of ferrous chloride, chromium chloride, chromium iron mixed solution have been studied. The results show Fe(II)/Fe(III) redox possessing a good reversibility, and Cr3+enhances Iron redox reversibility. Cr(II)/Cr(III) redox have a good reversibility in the presence of a catalyst.In order to study the iron-chromium redox flow battery performance. Charge-discharge performance of mixed and unmixed electrolyte redox flow battery with Nafionl15membrane have been studied. The results showed output energy of mixed electrolyte battery is higher20.8%than unmixed electrolyte battery. Effect of400℃heat-treated graphite felt electrode on the battery performance has been studied, the results shows output power of battery with heat-treated graphite felt is higher95.4%than untreated graphite felt, coulombic efficiency is higher5.0%than the latter, voltage efficiency is higher13.1%than the latter, the energy efficiency is higher15.1%than the latter. SPEEK membranes with different sulfonation were preparated, the results show SPEEK membrane ion capacity, water absorption, swelling ratio, electrical conductivity, ion permeability are increased with increasing degrees sulfonation of membranes. Performance of battery used SPEEK membrane with different degrees sulfonation is tested, SPEEK47.9%display a better performance, output energy density, coulombic efficiency, voltage, efficiency, energy efficiency are88.8%,89.9%,79.8%,6.9mWh/ml, respectively. Battery performance is better than Nafion115membrane of85.6%,91.0%,77.9%,6.9mWh/ml.Nanofiltration membranes were prepared by interfacial polymerization. Both methods were adopted, one is PP was soaked in the aqueous phase, then the reaction occurs in the organic phase, the other is PP was soaked in the organic phase, then the reaction occurs in the aqueous phase. Performance of battery used nanofiltration membrane was tested, the results showed a first method for preparing membrane has a better battery performance.