Solid oxide cells are made of ceramics. In the manufacturing process a number of methods from the ceramic industry are used.
Anode support
The first step is to make the cell support. This is the layer which gives the cell sufficient mechanical strength to be handled. In our standard cells the anode layer is the support. It is made of yttria stabilized zirconia (YSZ) mixed with nickel oxide. The materials are milled to a fine powder which is mixed with various solvents and additives to form a slurry. In a tape caster the slurry flows from a container on to a conveyer belt where the slurry is drawn slowly past a knife which determines the thickness of the cast anode support layer. We use a thickness of 300 μm (0,3 mm). The conveyer belt continues through a section where the anode support is dried.
When the support layer is dry, it is cut out in the required shape and size.
Active anode layer and electrolyte
On top of the anode support the active anode layer is put. This consists of YSZ and nickel oxide in a slightly different composition. On top of that a YSZ electrolyte with a thickness of approx. ca. 10 μm is deposited. Both layers are sprayed on in a spray robot. 
Sintering
The resulting 'half cell' is now sintered at high temperatures in a furnace. The ceramic particles in the cell soften and stick together and the half cell becomes hard upon cooling. During sintering the cell shrinks by approx. 20%.
Cathode
After the sintering, the cathode layer is put on in the spray robot. After this the cell is sintered again.
The finished cell has high mechanical strength and flexibility which is important for cell handling and assembly of the stacks. The picture below shows the flexibility of one of our 18 cm×40 cm cell.
Pre-pilot plant
In 2002 a pre-pilot plant was inaugurated at Risø. This makes it possible to manufacture cells on a scale approaching industrial production. The plant is an important part of the collaboration between Risø and the Danish company Haldor Topsøe A/S to commercialize the Danish cells.
The pre-pilot plant has a capacity of several thousand cells per year. This makes it possible to optimize production processes and to undertake systematic studies of the cell reproducibility. For instance, it is now possible to make cells with low curvature and small thickness variations which is important for their use in stacks. The cells are used partly for testing at Risø, partly for stack development at Haldor Topsøe A/S. The experiences from the pre-pilot plant will play a central role when an industrial production facility is established. |