Cathode materials for lithium ion batteries

A process of forming a coated cathode active material particle, the process comprising:

• preparing a cathode active material precursor particle in aqueous solution, the preparing comprising:
• providing an aqueous acidic solution of a metal ion and an aqueous basic solution;
• and
• combining the aqueous basic solution and the aqueous acidic solution to effect co-precipitation of the cathode active material precursor as a particle;
• wherein a concentration of the metal ion is continuously increased or reduced during formation of the cathode active material precursor particle such that the cathode active material precursor contains an increasing or decreasing metal concentration along a radius of the particle;
• coating the cathode active material precursor particle in aqueous solution with a coating material precursor to form a coated cathode active material precursor particle wherein the coating material precursor comprises Al(OH)3, Al2(CO3)3, Al2(C2O4)3, AlF3, AlPO4, Zr(OH)4, Ti(OH)4, Mg(OH)2, Zn(OH)2, ZnCO3, or Zr(CO3)2;
• lithiating or sodiating the coated cathode active material precursor particle in aqueous solution with a lithium or sodium source material to form a lithiated or sodiated coated cathode active material precursor particle;
• collecting the lithiated or sodiated coated cathode active material precursor particle;
• and
• sintering the lithiated or sodiated coated cathode active material precursor particle to form the coated cathode active material particle.