Modification And Electrochemical Performance Of Fe(VI)-based Materials As Cathodes Of Super-iron Battery

Since the super-iron battery, regarding a revolutionary technology in the cell field, has beeninvented at the end of the 1990s, it becomes a new hotspot due to many attractive advantages. Inthis thesis, the preparation and physiochemical properties of potassium ferrate, as well as itseletrochemical performance, were systematically investigated.In the experiments, we introduced an improved hypochlorite oxidation method forpreparation of potassium ferrate using potassium hydroxide instead of sodium hydroxide in theprocess. The effect of conditions on the purity and productivity of potassium ferrate was studied.The purity was analyzed by method of chromite oxidation. The experimental results demonstratethat the purity and productivity of the products could be apparently improved, more than 94%purity and more than 80% yield, while alkali concentration in reaction was controlled at10.5mol·L-1, temperature at 0~5℃ and amount of ferric nitrate at 85%~95%. The effect of loads, raw material purity and the other conditions on performance of super-ironbattery was studied as cathodes using potassium ferrates. The results show that, the super-ironbattery is unsuitable to high-power discharge without the additives. So potassium ferrate must bemodified in order to enhance its discharge performance.One of these innovations in the paper is that the modification of potassium ferrate was studiedby fluorinated graphite. Its discharge performance and storage characteristics were investigated.These results indicate that fluorinated graphite can improve discharge efficiency of super-ironbattery at high-current discharge. Adding 15% of fluorinated graphite, whose fluorinated rate is55%~61%, is the best. The discharge efficiency could reach more than 90% in the discharge of71.3 Ohm, and amount to 50% in the discharge of 10.5 Ohm. In addition, the super-iron battery isinstability in saturated alkali solution, and storage ability is poor.The second innovation in the paper is that the crystallizations and heated stability ofpotassium ferrate were studied by XRD and TG/DTA, and that cell materials were analyzed byFTIR and XRD. It is found that no new peaks are appeared by FTIR and XRD after mixingpotassium ferrate with fluorinated graphite and expanded graphite.