Varta Batterie Aktiengesellschaft

Peter Endres

Hans-Walter Praas

Sibylle Kemmler-Sack

Suitable as active cathode material for an electrochemical lithium secondary cell are oxygen-deficient spinels Li,Mn,O,, where 0&lE;x&lE;0.33 and 0.01&lE;&dgr;&lE;0.5. Their region of existence in a phase diagram laid out between the corner points MnO, MnO,and Li,MnO,for lithium manganese oxide compounds is defined by the corner compounds LiMn,O,, Li,Mn,O,, Li,Mn,O,and Li,Mn,O,, all the compounds along the lines LiMn,O,&mdash;Li,Mn,O,and LiMn,O,&mdash;Li,Mn,O,being excepted. The spinels are produced by a modified ceramic process from a mixture of Li-containing and Mn-containing starting substances whose reaction product is reduced by roasting in an Ar/H,atmosphere. The Li components x can be replaced partially or completely by foreign monovalent or multivalent cations from the series consisting of Co, Mg, Zn, Ni, Ca, Bi, Ti, V, Rh or Cu.

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Rottenburg, Germany

Peter Endres