Process for cathode active material precursor preparation

Process for producing a cathode material precursor having a desired active material target ratio for use in a lithium-ion secondary cell, the process comprising the steps:

• a) providing a leachate comprising one or more active materials selected from Ni, Co and Mn;
• b) identifying ionic impurities comprised in the leachate, and determining the concentration of each ionic impurity and of each active material in the leachate;
• c) adjusting the concentration of the one or more active materials in the leachate based on a total concentration of ions in the leachate;
• and
• d) raising the pH of the leachate to a level causing coprecipitation of the one or more active materials at a ratio corresponding to the desired active material target ratio for the precursor and causing coprecipitation of a minimum amount of ionic impurities, to obtain the cathode material precursor having the desired active material target ratio.