Sodium metal oxide material for secondary batteries and method of preparation

A method of preparing a sodium metal oxide material comprising NaxMyCozO2-δ, where M is one or more of the following elements:

• Mn, Cu, Ti, Fe, Mg, Ni, V, Zn, Al, Li, Sn, Si, Ga, Ge, Sb, W, Zr, Nb, Mo, Ta, 0.7≤x≤1.3, 0.9≤y≤1.1, 0≤z<0.15, 0≤δ<0.2 and wherein the average length of primary particles of said sodium metal oxide material is between 2 and 10 μm, said method comprising the steps of:
• a) mixing precursor materials comprising sodium salt and a salt of at least one of the following elements:
• Mn, Cu, Ti, Fe, Mg, Ni, V, Zn, Al, Li, Sn, Si, Ga, Ge, Sb, W, Zr, Nb, Mo, Ta, to a mixed precursor, wherein the mixed precursor comprises carbonate;
• b) placing the mixed precursor in an oven and heating the oven to a temperature of up to a temperature of between 800 and 1000° C. to provide the sodium metal oxide material;
• and
• c) cooling the sodium metal oxide material to room temperature in an atmosphere with less than 100 ppm CO2;
• wherein step b) comprises the sub-steps of:
• b1) heating the oven to a first temperature T1 between 900 and 1000° C.;
• b2) maintaining the temperature of the oven at the first temperature T1 until a specific phase distribution between P2 and O3 phases is achieved;
• b3) cooling the oven to a second temperature T2, where T2 is between 800 and 950° C. and wherein T2 is 50-150° C. lower than T1;
• and
• b4) maintaining the temperature of the oven at the second temperature T2 until the sodium metal oxide material is substantially carbonate free.