Sodium metal oxide material for secondary batteries and method of preparation

1 . A sodium metal oxide material for an electrode of a secondary battery, said sodium metal oxide material comprising: Na x M y Co z O 2-δ , where M is one or more of the following elements: Mn, Cu, Ti, Fe, Mg, Ni, V, Zn, Al, Li, Sn, Sb, and where 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 3 and 10 μm.

2 . A sodium metal oxide material according to claim 1 , wherein z=0.

3 . A sodium metal oxide material according to claim 1 , wherein the primary particles have a length and a thickness, where the thickness is smaller than the length, and where the average thickness of primary particles is between 1.0 and 4.0 μm.

4 . A sodium metal oxide material according to claim 1 , wherein M contains Ni and at least one further metal chosen from the group of: Mn, Cu, Ti, Fe, Mg.

5 . A sodium metal oxide material according to claim 1 , wherein M contains Ni and Mn.

6 . A sodium metal oxide material according to any of the claim 1 , wherein M contains Ni, Mn, Mg and Ti.

7 . A sodium metal oxide material according to claim 1 , wherein the sodium metal oxide material is a mixed phase material comprising the P2 and O3 phases.

8 . A sodium metal oxide material according to claim 7 , wherein the sodium metal oxide material comprises 20-40 wt % P2 phase and 60-80 wt % O3 phase.

9 . A sodium metal oxide material according to claim 1 , wherein the tap density of said sodium metal oxide material is between 1.5 and 2.5 g/cm 3 .

10 . A sodium metal oxide material according to claim 9 , wherein the tap density of said sodium metal oxide material is between 1.7 and 2.2 g/cm 3 .

11 . A sodium metal oxide material according to claim 1 , wherein the BET area is between 0.3 and 1 m 2 /g.

12 . A sodium metal oxide material according to claim 1 , wherein the sodium metal oxide material has been manufactured by mixing of precursor materials in a dispersion, drying and heating in an oven.

13 . A method of preparing a sodium metal oxide material comprising: Na x M y Co z O 2-δ , where M is one or more of the following elements: Mn, Cu, Ti, Fe, Mg, Ni, V, Zn, Al, Li, Sn, Sb, 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 3 and 10 μm, said method comprising the steps of:

a) mixing precursor materials comprising sodium salt and a salt or oxide of at least one of the following elements: Mn, Cu, Ti, Fe, Mg, Ni, V, Zn, Al, Li, Sn, Sb, in a dispersion to a mixed precursor, wherein the mixed precursor comprises carbonate;

b) drying the mixed precursor to a mixed precursor having a moisture content between 2 and 15 wt %;

c) 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

d) cooling the sodium metal oxide material to room temperature in an atmosphere with less than 100 ppm CO 2 .

14 . A method according to claim 13 , wherein the heating of step c) comprises the steps of:

c1) heating the oven to a first temperature T 1 between 900 and 1000° C.;

c2) maintaining the temperature of the oven at the first temperature T 1 until a specific phase distribution between P2 and O3 phases is achieved;

c3) cooling the oven to a second temperature T 2 , where T 2 is between 800 and 950° C. and wherein T 2 is 50-150° C. lower than T 1 ;

c4) maintaining the temperature of the oven at the second temperature T 2 until the sodium metal oxide material is substantially carbonate free.

15 . A sodium metal oxide material for an electrode of a secondary battery, said sodium metal oxide material comprising: Na x M y Co z O 2-δ , where M is one or more of the following elements: Mn, Cu, Ti, Fe, Mg, Ni, V, Zn, Al, Li, Sn, Sb, and where 0.7≤x≤1.3, 0.9≤y≤1.1, 0≤z<0.15, 0 δ<0.2, and wherein the average volume of primary particles of said sodium metal oxide material is at least 8 μm 3 .