Abstract: A process for producing a lithium-manganese-rich layered oxide cathode material or a lithium-manganese-rich layered oxide cathode material precursor includes co-precipitating a dissolved Li compound and a dissolved Mn salt selected from the group consisting of Mn(CH3COO)2, Mn(NO3)2, MnSO4, and mixtures thereof, from an aqueous solution, in the presence of a precipitator which reacts at least with the dissolved Mn salt to form a carbonate, thereby providing a precipitate which includes MnCO3 and a lithium compound as a lithium-manganese-rich layered oxide cathode material precursor. The invention extends to a lithium-manganese-rich layered oxide cathode material or a lithium-manganese-rich layered oxide cathode material precursor, to an electrochemical cell, and to methods of making and operating an electrochemical cell.