An Alkaline Periodate Cathode and Its Unusual Solubility Behavior in KOH

Abstract

An unusual solubility domain for KIO 4 in KOH solution which is consistent with a potential use of periodate as a cathode for alkaline batteries is reported. The solubility of KIO 4 first increases, then drops from 2.9 M to Ͻ 10 −4 M with increase from 6 to 10 M KOH. Periodate exhibits an intrinsic 2e-reduction to IO 3 − . Zn anode alkaline batteries are studied with KIO 4 and NaIO 4 cathodes, have a potential of 1.4-1.5 V, and discharge to over 95% of the intrinsic capacity. The cathode also exhibits good quasi-reversibility ͑rechargeability͒ with an alkaline metal hydride anode.Periodates are the highest valent form of iodine compounds, and have long been used as strong oxidants in organic synthesis. 1,2 Periodic alkali salts are also widely used for quantitative analysis, in their reduction in dilute aqueous media to iodate, for the determination of a variety of organic or inorganic compounds in accordance with quantitative reactions. 3,4 Potassium and sodium periodate are among the most common of the alkali periodate salts and are commercially available in pure form. 3 In addition to their applications in the analytical chemistry and organic synthesis, periodate alkaline salts are used for chemical mechanical polishing ͑CMP͒ slurries 5 and etchants. 6 Each of these applications of periodate alkaline salts is based on their strong oxidizing properties. As an oxidant in alkaline media IO 4 − forms IO 3 − via a two-electron reductionAqueous KOH is the commonly used electrolyte for alkaline primary ͑zinc anode͒ and alkaline secondary ͑metal hydride or cadmium anode͒ batteries. The latter cells contain a nickel oxide cathode, while common primary batteries contain either silver or manganese oxide cathodes. 7 Advanced cathodes are needed to further improve these batteries and we have explored various unusual alkaline cathodes including solid sulfur, 8 hexavalent or "super-iron," 9-12 manganates, 13 fluorinated graphites, 14 and hydrogen peroxide. 15 Both potassium periodate and sodium periodate are white crystalline or granular powders ͑KIO 4 : density, d = 3.62 g cm −3 , formula weight, FW KIO 4 = 230 g/mol, melting point, mp = 582°C; NaIO 4 : d = 3.87 g cm −3 , FW NaIO 4 = 214 g/mol, mp = 300°C͒. 16 In industry, potassium and sodium periodates are usually prepared by chlorine or persulfate oxidation of iodate. 17 Potassium inorganic salts often are highly soluble in water, although the solubility of KIO 4 in pure water is a relatively low 0.42 g/100 g H 2 O ͑or 0.018 M͒ at 20°C. 16 In this study, an unusual lower solubility extreme for KIO 4 in concentrated aqueous KOH is demonstrated, and periodate is also probed as an effective alkaline battery cathode. ExperimentalSolubility of periodate in KOH solution.-The solubility of KIO 4 or NaIO 4 , in aqueous KOH ͑all p.a. grade from ACROS͒ is measured with a "step-approach" methodology.Step ͑1͒: A mass of either periodate salt, m KIO 4 or m NaIO 4 , is observed as soluble in approximately 25 mL of each studied concentration of KOH at 22°C.Step ͑2͒: m KIO 4 or m NaIO...

Multi-electron reaction materials for high energy density batteries

“…17 Some high valence compounds, such as periodate and AgMnO 4 , can also be potentially used as cathode materials with multi-electron transfer in alkaline solution, offering high specific capacities. 18,19 Most importantly, some of these high valence compounds (including ferrates) appear to have quasi-reversibility on the extended conductive matrices composed of high surface area Pt, Ti and Au, providing a chance to fabricate alkaline rechargeable batteries with a metal hydride anode after minimizing the interference with the anode. 19,20 The reversible charge transfer of ferrate cathodes in nonaqueous electrolyte is mainly related to the electrochemical window and chemical composition of the electrolyte and solvent used.…”

“…18,19 Most importantly, some of these high valence compounds (including ferrates) appear to have quasi-reversibility on the extended conductive matrices composed of high surface area Pt, Ti and Au, providing a chance to fabricate alkaline rechargeable batteries with a metal hydride anode after minimizing the interference with the anode. 19,20 The reversible charge transfer of ferrate cathodes in nonaqueous electrolyte is mainly related to the electrochemical window and chemical composition of the electrolyte and solvent used. 18,20,21 Both the lithiation/delithiation of the active mass and the reduction/ oxidation of the Fe(VI/III) coexist in the charge and discharge process of ferrates in nonaqueous electrolyte.…”

Development of High-Capacity Periodate Battery with Three-Dimensional-Printed Casing Accommodating Replaceable Flexible Electrodes

“…Periodates (IO 4 – ) are strong oxidants with the highest possible oxidation state for iodine. Periodic acid and its Na and K salts have been used in organic reactions. − The iodine­(VII) and iodine­(V) compounds show positive electrode potentials, which makes them a viable material for electrochemical storage. , Yet, there have been few reports on periodate-based electrodes, , where Na and K periodate cathodes have shown two-electron reduction to IO 3 – in the alkaline environment. There are also a few reports on IO 3 – -based electrodes. , A combination of KIO 3 cathode and H 2 SO 4 electrolyte has shown the reduction of IO 3 – to I 2 .…”

Nanoparticle Facilitated Charge Transfer and Voltage of a High Capacity VB2 Anode

“…Hence, we have studied, or introduced, a range of multiple electron per molecule redox materials for charge storage. These range from the two electron redox chemistry of solid sulfur, 1 to the three electron redox chemistry of hexavalent super irons 2,3 or aluminium, 4 as well as multiple electron per molecule transfer in peroxides, 5 polyiodides, 6 permanganates, 7 metal chalcogenides, 8 iodates, 9 and stannates; 10 selective examples are cited in the references.…”