Abstract: Nonaqueous electrolyte rechargeable cells may contain an excess of negative electrode material to improve the rechargeability. This excess of negative electrode material can form brittle alloys with noncorrosive current collector metals in positive electrodes at low cell voltages. The invention discloses that an excess of current collector material in the positive electrode directly opposite to the negative electrode improves the safety characteristics of the rechargeable cells during overdischarge and multiple voltage reversal abuses.

Abstract: Lithiated nickel dioxide cathode-active materials for electrochemical cells aving the formula Li.sub.x Ni.sub.2-x-y M.sub.y O.sub.2, with x being between about 0.8 and about 1.0, M being one or more metals selected from cobalt, iron, chromium, titanium, manganese and vanadium, and y being less than about 0.2, with the proviso that y is less than about 0.5 for cobalt, which material is substantially free of lithium hydroxide and lithium carbonate. The materials are prepared by providing a substantially homogeneous dry intermediate mixture of a starting material containing a nickel compound selected from nickel oxide, nickel hydroxide, and mixtures thereof, and optionally including one or more oxides or hydroxides of a transition metal selected from cobalt, iron, chromium, titanium, manganese and vanadium, together with between about a 10 and about a 25% stoichiometric excess of lithium hydroxide. The mixture is heat treated at a temperature above about 600.degree. C.