Fe(VI) Catalyzed Manganese Redox Chemistry:  Permanganate and Super-Iron Alkaline Batteries

Abstract

In principle, alkali permanganates represent a substantial cathodic charge source for electrochemical storage, but high rate charge transfer has been inefficient. This study presents a novel Fe(VI) species (super-iron) and manganese redox chemistry synergism. Also presented is the high discharge energies from cathodes which utilize this phenomenon in a conventional cylindrical battery configuration. Batteries formed with a cathode combining BaFeO 4 and KMnO 4 , and using a conventional zinc alkaline anode in an AAA cylindrical cell configuration, exhibit an unusually high discharge capacity of 2.2 Wh. The discharge efficiency of solid alkaline permanganate or manganate cathodes is probed, and improved charge transfer of Mn(VII) redox chemistry in the presence of Fe(VI) is demonstrated. In a reciprocal manner, enhancement of Fe(VI) charge transfer are demonstrated upon inclusion of manganese salts, and also that added cesium further improves the combined Fe(V)/Mn(VII) cathode.

Advances in electrochemical Fe(VI) synthesis and analysis

“…One interesting observation toward an interpretation of the different stabilities evident is the higher trace Mn concentrations of Mn for the in situ electrochemically compared to chemically synthesized BaFeO 4 [31]. Manganese can be concurrently oxidized with the iron to form high valence manganese oxide salts, and can stabilize Fe(VI) salts by the renewal of decomposed Fe(III), according to reactions such as [12,20]:…”

Preparation and stability study of potassium ferrate (VI) coated with phthalocyanine for alkaline super-iron battery

“…It is obvious from above data that the capacity of bare K 2 FeO 4 decreases dramatically at first, and then the downtrend appears to be moderating. As proposed by Licht [18][19][20], the reason for this tendency can be ascribed to the fact that Fe (VI) cathode is easy to decompose into Fe (III) overlayer on the surface of electrode in the beginning. Over time, although the bulk inside K 2 FeO 4 still has activity, but the Fe (III) overlayer on the surface restrain the further decomposition of K 2 FeO 4 cathode, so the decomposition of K 2 FeO 4 slows down.…”

Effect of manganese compounds on synthesis of ferrates(VI)

“…Так, в [12] считают, что добавление небольшого коли чества (2-5 %) перманганата или манганата к продук там восстановления ферратов (гидроксиду или оксиду железа(III)) способствует переходу Fe(III) в Fe(VI), например по реакциям:…”

“…Следует заметить, что для всех из ученных производных марганца Mn(II) и Mn(IV) при взаимодействии их с избытком FeO 4 2-, в растворе был идентифицирован только манганат ион, т. е. в 14-16 М ОН -окислительная способность ферратов ниже, чем у перманганатов, но выше чем у манганатов. Эти вы воды находятся в согласии с [14], не совпадают с [13] и частично совпадают с [12].…”