Demonstration of a Novel Alkaline Battery Cathode Material: Periodate Salts
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0973-BB04-02
Demonstration of a Novel Alkaline Battery Cathode Material: Periodate Salts Stuart Licht and Xingwen Yu Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Blvd., Boston, MA, 02125
ABSTRACT An unusual solubility domain for KIO4 in KOH solution is observed, which is consistent with a potential use of periodate as a cathode for alkaline batteries. With increasing alkalinity, the solubility of KIO4 first increases, then drops from 2.9 M to < 10-4 M with increase from 6 to 10 M KOH. The unusual rapid transition from high to low solubility with increasing KOH is attributed to the formation of insoluble periodate complex. Accompanying the favorable low solubility in concentrated KOH is a high degree of cathodic electroactivity in accord with two IO3-. Low cathode salt solubility minimizes interference with the anode. electron storage: IO4Zn anode alkaline batteries are studied with KIO4 and NaIO4 cathodes, have a potential of 1.41.5 V and discharge to over 95% of the intrinsic 2e- charge capacity. The cathode also exhibits good quasi reversibility (rechargeability) with an alkaline metal hydride anode.
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INTRODUCTION As the highest valent form of iodine compounds, periodates are generally strong oxidants, and has been used as the catalyst in organic synthesis for many years [1, 2]. Moreover, periodic alkali salts can be reduced in dilute aqueous media to iodate by certain organic or inorganic compounds in accordance with quantitative reactions. This makes periodic alkali salts widely used as analytical laboratory reagents for the determination of the reducing agents in analytical chemistry area [3, 4]. Among these periodic alkali salts, Potassium periodate and sodium periodate introduce no complications being obtainable in sufficiently pure form and, moreover, are commercially available [3]. Both potassium periodate and sodium periodate are white crystal or granular powder (KIO4: Density is 3.62, melting point is 582 0C; NaIO4: Density is 3.87, melting point is 300 0C) [5]. In industry, potassium periodate and sodium periodate are usually prepared by oxidation of iodate by chlorine or persulfate [6]. In addition to their applications in the analytical chemistry and organic synthesis, more recently, periodate alkaline salts are used for chemical mechanical polishing (CMP) slurries [7] and etchants [8]. Each of these applications of periodate alkaline salts are based on their strong oxidizing properties. As an oxidant in alkaline media IO4- forms IO3- via a two electron reduction: IO3- + 2OH(1) IO4- + H2O + 2eAqueous KOH is the commonly used electrolyte for alkaline primary (zinc anode) and alkaline secondary (metal hydride or cadmium anode) batteries. The latter cells contain a nickel oxide cathode, while common primary batteries contain either silver or manganese oxide cathodes [9]. Advanced cathodes are needed to further improve these batteries and we have explored various unusual alkaline cathodes including solid sulfur [10], hexavalent or "superiron" [11-14], manganates [15], flu
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