Effects of additives and temperature on iron electrode behavior in KOH electrolytes. [Addition of K/sub 2/S, LiOH or FeO to KOH]

Technical Report · Mon Apr 01 04:00:00 EST 1985

OSTI ID:5533634

Poa, D S; Miller, J F; Yao, N P

The effect of temperature (-20 to 45/sup 0/C), electrolyte additives (K/sub 2/S, LiOH, and FeO), and KOH concentration on the electrochemical behavior of iron electrodes in KOH electrolytes was studied by the cyclic voltammetric method. Experimental results indicated that the charging efficiency of the iron electrode will be decreased at lower temperatures. To achieve the same state of charge as that obtained at higher temperatures, a higher charging voltage is required at lower temperatures. However, the higher charging voltage will increase hydrogen evolution, which will cause the charging efficiency of the iron electrode to decrease. The addition of K/sub 2/S to the KOH electrolyte can effectively suppress the H/sub 2/ evolution on the iron electrode during charging. However, the incorporation of sulfur-bearing anions onto the electrode surface will accelerate the electrode reactions and cause the electrode to be less stable during repetitive cycling. The addition of LiOH to the electrolyte will be beneficial to the stability of the iron electrode, particularly at the transitions from lower to higher oxidation states (deep discharge). The saturation of the KOH electrolyte with FeO appeared to cause significant changes in the mechanisms and reaction rates of the electrode reduction-oxidation processes because of the competing reactions of Fe(II) species which become more available at the iron electrode surface. In electrolytes of 7.0 to 10.0 M KOH, the reaction rates of iron electrodes were much lower than those obtained in electrolytes of lower KOH concentrations (0.5 to 4.0 M). This decrease in reaction rates in more concentrated electrolytes was probably caused by the increased formation of solid film products of higher oxidation states at the electrode surface. 22 refs., 21 figs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5533634
• Report Number(s): ANL/OEPM-85-2; ON: DE85011901
• Country of Publication: United States
• Language: English

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25 ENERGY STORAGE
250903* -- Energy Storage-- Batteries-- Materials
Components
& Auxiliaries
ADDITIVES
ALKALI METAL COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
DISSOLUTION
ELECTROCHEMICAL CELLS
ELECTRODES
ELECTROLYTES
ELEMENTS
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
HYDROXIDES
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IRON
IRON COMPOUNDS
IRON OXIDES
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MEDIUM TEMPERATURE
METALS
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OXIDATION
OXIDES
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PERFORMANCE
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TEMPERATURE DEPENDENCE
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TRANSITION ELEMENTS
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