5523182 Enhanced nickel hydroxide positive electrode materials for alkaline rechargeable electrochemical cells

A positive electrode material comprising particles (1) including at least one electrochemically active hydroxide and a substantially continuous, uniform encapsulant layer (4) surrounding the particles of positive electrode material. The encapsulant layer is formed from a material which, upon oxidation during processing or charging of the electrode, is convertible to a highly conductive form and upon subsequent discharging of the electrode does not revert to its previous form. Preferably, the electrochemically active hydroxide includes at least nickel hydroxide. The encapsulant layer is preferably formed from at least cobalt hydroxide or cobalt oxyhydroxide and is formed by precipitation from a cobalt salt solution, which can be a cobalt sulfate solution. Electrodes which include the electrochemically active material as well as a precipitation process for forming the material are disclosed.