Provided herein is a method for preparing a cathode based on an aqueous slurry. The cathode slurry comprises a cathode active material, especially a nickel-containing cathode active material, with improved stability in water. Pre-treatment of nickel-containing cathode active materials may improve stability of the cathode by preventing undesirable decomposition of the material. In addition, battery cells comprising the cathode prepared by the method disclosed herein exhibit impressive electrochemical performances.