Next-generation 3D-printed solid oxide electrolysis cells

High-temperature (solid oxide) electrolysis cells (SOECs) may play a key role in the decarbonization of various sectors. In addition to hydrogen, SOECs also enable the production of syngas or carbon monoxide while also having the highest electrical efficiency of all electrolysis technologies. Due to these properties, they could be used as a highly efficient power-to-X technology in the steel, cement and chemical industry. Moreover, the generated product gases can also be stored and later converted back into electricity using reversible SOECs. This may enable a further increase in the share of fluctuating renewable energy sources.

In this project, a new cell design is being developed and combined with innovative materials to significantly improve the power density and lifetime of SOEC systems. For this purpose, a ceramic 3D printing process is used to produce fuel electrode-supported cells with an increased active surface area compared to conventional planar cells. In addition, flow fields and gas channels are introduced directly into the cells. This enables simplification and considerable material savings of the expensive interconnect plates and thus reduces manufacturing costs. 

CFD and FEM simulations are carried out in advance in order to optimize the gas flow and structural mechanics while keeping the surface area as large as possible. The results of the simulations are directly implemented in the actual 3D printing process. The lithography-based ceramic manufacturing (LCM) method is used for the ceramic 3D printing of the fuel electrodes consisting of a Ni-YSZ cermet or gadolinium-doped cerium oxide.

Since serious degradation phenomena often occur on conventional air electrodes in SOECs, the promising material class of rare earth nickelates such as (La,Pr)2NiO4+δ will be investigated. These materials can accommodate additional oxygen ions under the strongly oxidizing conditions in SOEC operation. This favors ion transport and could thus prevent the formation of oxygen gas inside the cell and the associated degradation. 

In this project, a systematic investigation for the optimal doping of this material class will be carried out. Using a combinatorial deposition method, Ca doping at the (La,Pr) site and Fe doping at the Ni site will be investigated. The aim is to improve both the thermal stability and the kinetics. The use of Ca and Fe as doping materials also reduces the proportion of critical raw materials (La, Pr, Ni) and thus also the costs. After the production of thin YSZ electrolyte layers using sputtering, the newly developed air electrodes are applied to the 3D-printed fuel electrode substrates. This project therefore covers the entire cell production process. 

Long-term experiments are required to characterize the performance of these cells over their entire lifetime. Typical test periods last more than 5000 hours and are thus time and resource consuming. Therefore, shortened test programs are being developed in this project, which specifically induce accelerated degradation. This enables not only the prediction of long-term behavior, but also the definition of suitable operating parameters in order to maximize the lifetime.

Funding