Abstract: The invention proposes an open alkaline accumulator of the nickel cadmium or nickel metal hydride type comprising at least one positive electrode, at least one negative electrode and at least one separator, said separator comprising a microporous membrane of polyolefin grafted with an ethylenically unsaturated monomer, and on either side of said membrane, at least one layer of polyolefin with a fibrous structure. Said accumulator has a lesser risk of thermal runaway upon charging at constant voltage, and a longer life time. The invention lies in the discovery that the use of a microporous membrane of polyolefin grafted with an ethylenically unsaturated monomer in an open alkaline accumulator of the nickel cadmium or nickel metal hydride type, provides a barrier to oxygen gas. The invention is extended to the method for charging at constant voltage said alkaline accumulator.

Abstract: A paste for impregnating a three-dimensional metal sponge porous support, which impregnated porous support is dried to provide an electrode for an electrochemical cell. The paste comprises (i) an electrochemically active material selected from a metal hydride and a metal hydroxide in an amount of from 40% to 60% of the weight of the paste, and (ii) a gel containing xanthan in an amount of from 0.5% to 2% of the weight of the gel. The paste has a yield point greater than the shear stress due to the gravity so that the paste does not flow out of the impregnated support. Also disclosed is a method of making an electrochemical cell electrode, comprising the steps of preparing the above-described paste, impregnating the paste into a three-dimensional metal sponge porous support, and drying the paste. The inventive paste is advantageously retained in the support during the drying step.