Research On The Alkaline Batteries With Ferrate(VI) As Cathode Active Material

In this thesis, the uper-iron alkaline batteries .utilizing insoluble ferrate(VI)-K₂FeO₄ as cathode active material, was more systematically investigated by the mothods of EB, XRD, and CV. The fitness of four negative electrode materials such as Al, Fe, Zn, Cd ,and of six membranes materials: microfiber glass mat separator, polyethylene, polypropylene, polyvinyl chloride, vinylon, soapnated cellulose acetate ,and of four current collects: carbon fiber; nickel foam; nickel foam sthongthened by iron wire net, punched silver grid in the super-iron alkaline batteries was comparatively studied. The influence of two storaged method (with and without electrolyte) and two impurities (ZnO,Fe(OH)3) to the experiment cell's self-discharge nature was also comparatively studied .At last , the nature of discharge .structure and electrochemistry of experimental cell with K2FeO4 as cathode active material prepared by three different methods: high temperature reaction ,hypochlorite oxidizing and electrolysis, was comparatively studied .We can conclude:i) The open-circuit potential and the flat of work potential and the percent of capacity of K2FeO4 till 1.0V during the discharge at constant load of experimental cells decreased by the order of Al/K2FeO4, Zn/K2FeO4, Cd/K2FeO4 ,Fe/K2FeO4. As for the nature of charge-discharge cycle, Cd/K2FeO4 Fe/K2FeO4 Zn/K2FeO4.In water solute electrolyte , although Al/K2FeO4 cann't be used as storage battery ,it have great potential as primary cell or storage cell from the aspect of its discharge capacity .discharge power.ii)The membrane materials of polymer may be oxidized by ferrate(VI)because of their strong or weak reductivity ,when they were directly connect with the ferrate(VI) cathode in experiment cell., so the the cathode's capacity decreased. According to the observed experiments that the Na2FeO4 solution with the same concentration and volume were decomposed by the same area of different membrane ,we learned the order of the decomposing rate of Na2FeO4 caused by different membranes: soapnated cellulose acetate > vinylon > polypropylene polyvinyl chloride = polyethylene microfiber glass mat. When they were respectively used as separator in Zn/K2FeO4 battery, the percent of capacity of the cathode active material Na2FeO4 were : microfiber glass mat's:93%; polyethylene's:68%; polypropylene's:56%;polyvinyl chloride's:47%; vinylon's:38%; soapnated cellulose acetate's:24%.Although Five of them (not concluding soapnated cellulose acetate) had very weak or weaker reductivity as separator in super-iron battery ,for which they were more suitable to being separator in super-iron battery . but they were easy to be soaked by water for being connect with KOH solution for long time , which led to cathode active material's decomposition ,thus they cann't be fit for being separator in super-iron battery . Polyvinyl chloride and polyvinyl chloride can resist to be oxidized . Soapnated cellulose acetate can prevent dissolved ferrate(VI) penetrating toward the anode and prevent dissolved cathode's discharge products penetrating toward the cathode.iii) With carbon fiber, nickel foam, nickel foam sthongthened by iron wire net .punched silver grid as cathode current collectors .form the percent of capacity of K2FeO4, carbon fiber was better than nickel foam, and the nickel foam sthongthened by iron wire net wasadvantaged to normal discharge of Fe/K2FeO4 ,but the Zn/K2FeO4 hadn't apparent virtue. As for Al/K2FeO4 and Zn/K2FeO4, nickel foam and punched silver grid had no apparent difference. In order to avoid the influence of trace metal to the stability of ferrate(VI) , carbon fiber was more suitable, but it led to the problem of being prepared of the cathode ,of emerging of the electrode's ear and of connecting between the base and shell.iv)The decomposition of K2FeO4 in the cathode was the main behaving pattern of the experimental cell's self-discharge, so many factors having influence to the decomposition of K2FeO4 can effect the self-discharge . (l)The fraction of the decompositio...