The Use and Behavior of Aluminum Anodes in Alkaline Primary Batteries

The two- to threefold reduction in over-al l theoretical reactant weight (and usually also volume) which results from replacing Zn by A1 in alkaline primary batteries could best be preserved in practice with a 3M KOH "self-regenerating " electrolyte in large (>1 kw) Al-air (or--O,) power sources, whereas mall Al-air (or--O ~ or--AGO) reserve cells should function best with a consumable 10M KOH solution. Special attention is given to the use of A1 in Al-air cells with porous C or, preferably, porous Ni air cathodes. Anode polarization and current efficiency data are presented for both the self-regen-erating and the consumable lectrolytes with and without several effective corrosion inhibitors consisting of alkyldimethylbenzylammonium salts and/or Hg with or without ZnO. It is concluded that optimum battery performance would result from the use of some of these inhibitors, as well as from el imina-tion of sulfides and other corrosion accelerators, use of highly pure A1 or specially resistant A1-Mg, A1-Zn, or A1-Hg alloys, effective heat removal, opera-tion at high current densities (preferably--~10 ma/cm') , and anode-electrolyte separation during periods of inaction. In spite of the highly attract ive anode charac-teristics of A1, all previous attempts (1-8) to uti l ize it in practical batter ies fai led (9-11) either be-cause of the format ion of passivating, resistive ox-ide layers in those electrolytes in which A1 oxides are not readi ly soluble (1-6, 12) or because of high rates of corrosion in those electrolytes in which the oxide layers are dissolved, e.g., in concentrated alkal i solutions (7, 8). Nevertheless, the author was interested in the possibi l ity of using A1 anodes under conditions where in the corrosive alkal ine electrolyte would be in contact with the metal dur-ing current drain only. Thanks to encouraging init ia l exper imenta l re-sults suggesting the possibi l i ty of achieving outputs of 1.0-1.Sv at current densit ies of up to 50 ma/cm" (cf. Fig. 3 and the re levant ext) and current effi-