Rechargeable electrochemical cell

Claim 1

A rechargeable electrochemical cell which is sealed from the external environment, comprising, in a chamber which is sealed from the environment: a positive electrode comprising an electrochemically active material selected from the group consisting of nickel hydroxide, silver oxide and manganese oxide; a negative electrode made of an electrochemically active material comprising LaNi n , n being between 4.8 and 5.4, wherein La may be partially substituted with an element selected from the group consisting of calcium, thorium, titanium, rare earth metals and yttrium, and wherein Ni may be partially substituted with an element selected from the group consisting of copper, chromium and iron, said LaNi n or substitution product thereof having a CaCu 5 crystal structure; and an aqueous electrolyte having a pH exceeding 7; wherein the quantity of the electrochemically active material of the negative electrode exceeds that of the positive electrode by at least approximately 15%, and in the fully discharged state of the positive electrode the electrochemically active compound of the negative electrode, as regards the excess, is at least partially present as a hydride, namely in the charged state.