Formulation of zinc negative electrode for rechargeable cells having an alkaline electrolyte
View Patent ↗A zinc electrode is provided for use in electrochemical cells having an alkaline electrolyte and high cycle life. The zinc electrode comprises a mixture of zinc oxide together with an inorganic fibre which contains silica and alumina. Preferably, the composition of the inorganic fibre is in the range of 80% to 99% alumina, and 1% to 20% silica. Typically, the zinc electrode will further comprise an inorganic fibre additive in the range of 2% to 15% by weight of the zinc oxide electrode. Also, the zinc electrode will typically further include 2% up to 10% of bismuth oxide.
1. An electrochemical cell comprising:
a zinc electrode comprising a mixture of zinc oxide together with an inorganic fibre; and
a buffered electrolyte comprising a salt of boric acid present in a concentration of between 0.6 and 1.3M, and a stoichiometric excess of alkali hydroxide between 2.7 and 5 moles per liter.
2. The electrochemical cell of claim 1 , wherein the zinc electrode further comprises 2% up to 10% of bismuth oxide.
3. The electrochemical cell of claim 1 , wherein the zinc electrode is provided on a matrix of copper or an alloy thereof.
4. The electrochemical cell of claim 1 , wherein the cell is provided in a power tool.
5. The electrochemical cell of claim 1 , wherein the electrolyte further comprises an alkali or alkaline earth fluoride.
6. The electrochemical cell of claim 5 , wherein the fluoride is present in an amount corresponding to a concentration range of 0.01 to 1 equivalents per liter of the electrolyte.
7. The electrochemical cell of claim 1 , further comprising a nickel positive electrode.
8. The electrochemical cell of claim 1 , further comprising a separator.
9. The electrochemical cell of claim 8 , wherein the separator wraps said zinc electrode.