Electrolyte for zinc metal oxide batteries - uses salt of boric, phosphoric or arsenic acid(s) with 0.02 to 3 equivs. excess hydroxide

摘要

A battery comprises (a) an anode having Zn (alloy) active material, (b) a cathode having metal (hydr)oxide active material and (c) an electrolyte comprising a salt prepd. by reaction of boric, phosphoric and/or arsenic acids with alkali(ne earth) hydroxide in amts. providing a stoichiometric excess of hydroxide of 0.02-3.0 equivs./1. The electrolyte is prepd. by mixing acid and hydroxide with excess hydroxide pref. yielding a pH >=9, esp. 9-14. The electrolyte reduces solubility of Zn anode prods., eliminating problems of shape change and dendric deposition, yet is sufficiently alkaline for satisfactory cathode performance. Cell cycle life is increased by a factor of 2.2-3.5 over cells having KOH electrolyte, e.g. 109-116 cycles for K borate-KOH, 27-31 cycles KOH electrolyte. Pref. the electrolyte salt is K or Na (meta)borate, (meta) phosphate or (meta)arsenate. The hydroxide is KOH or NaOH, esp. with 5-9 equivs./1 NaOH or KOH mixed with 2.0-8.98 equivs. boric acid, excess OH 0.02-3.0 equivs.