Storage structure of an electrical energy storage cell

1. An electrical energy storage cell comprising an air electrode configured for fluid flow communication with an air supply, an active storage material, and a solid state electrolyte disposed between the air electrode and the active storage material, the storage cell characterized by:

a first region of the active storage material; and

a second region of the active storage material;

wherein the first region has a higher porosity than the second region;

wherein the first region comprises a core region and the second region comprises a shell region, and further comprising a porous barrier layer disposed between the core region and the shell region.

2. The electrical energy storage cell as claimed in claim 1 ,

wherein the active storage material in the shell region and in the core region comprises iron and/or iron oxide.

3. The electrical energy storage cell as claimed in claim 1 ,

wherein the active storage material in the shell region is doped, the doping comprising one or more elements from the group of chromium, cobalt, aluminum, silicon, titanium and manganese.

4. The electrical energy storage cell as claimed in claim 1 ,

wherein the active storage material in the core region is doped, the doping comprising one or more elements from the group of molybdenum, vanadium, boron and bismuth.

5. The electrical energy storage cell as claimed in claim 1 ,

wherein the active storage material in the shell region has a porosity of less than 40%.

6. The electrical energy storage cell as claimed in claim 1 ,

wherein the active storage material in the core region has a porosity of less than 50%.

7. The electrical energy storage cell as claimed in claim 1 ,

wherein the active storage material in the shell region and in the core region has a particle size distribution having a d50 of less than 5 μm and a d90 of less than 10 μm.

8. The electrical energy storage cell as claimed in claim 1 , further comprising

an inert material incorporated in the active storage material of the shell region and of the core region.

9. The electrical energy storage cell as claimed in claim 8 ,

wherein the inert material is based on zirconia, yttrium-stabilized zirconia, alumina, yttria, calcium oxide, ceria or magnesium oxide or combinations thereof.

10. The electrical energy storage cell as claimed in claim 8 ,

wherein the inert material has a particle size distribution having a d50 of between 30 nm and 500 nm and a d90 of less than 2 μm.

11. The electrical energy storage cell as claimed in claim 10 ,

wherein the porous barrier layer comprises inert ceramic material.

12. The electrical energy storage cell as claimed in claim 10 ,

wherein the porous barrier layer has a thickness of less than 1 mm.

13. The electrical energy storage cell as claimed in claim 10 ,

wherein the porous barrier layer has an open porosity of more than 40%.

14. The electrical energy storage cell as claimed in claim 1 ,

wherein a volume ratio between the shell region and core region is in a range between 10:1 and 1:10.

15. The electrical energy storage cell as claimed in claim 11 ,

wherein the inert ceramic material is based on zirconia, yttrium-stabilized zirconia, alumina, yttria, calcium oxide, ceria or magnesium oxide or combinations thereof.

16. The electrical energy storage cell as claimed in claim 10 ,

wherein the porous barrier layer has a thickness of less than 500 μm.

17. The electrical energy storage cell as claimed in claim 1 , wherein the first region comprises a dopant effective to accelerate oxidation of the active storage material of the first region during charging of the electrical energy storage cell.

18. An electrical energy storage cell comprising an air electrode configured for fluid flow communication with an air supply, an active storage material, and a solid state electrolyte disposed between the air electrode and the active storage material, the storage cell characterized by:

a first region of the active storage material; and

a second region of the active storage material;

wherein the first region has a higher porosity than the second region;

wherein the second region comprises a dopant effective to slow oxidation of the active storage material of the second region during charging of the electrical energy storage cell.