As global demand for renewable energy continues to rise, energy storage technology faces unprecedented challenges. However, in recent years, reversible solid-state oxidation cell (rSOC) technology is attracting more and more attention as it shows great potential in terms of efficiency and application flexibility. The technology is unique in its ability to act as both a fuel cell and an electrolytic cell, making it revolutionary for long-term and seasonal energy storage.
Reversible solid-state oxidation batteries are composed of four main parts: electrolyte, fuel electrode, oxygen electrode and interconnector. The electrolyte is a solid layer that has good oxygen ion conductivity but does not conduct electricity. The fuel electrode and oxygen electrode are porous materials that can promote the diffusion of reactants inside them and carry out electrochemical reactions.
When rSOC operates in SOFC mode, oxygen ions will flow from the oxygen electrode to the fuel electrode, thereby realizing the oxidation reaction of the fuel; of course, in SOEC mode, the product is reduced to generate fuel that can be fed back.
Polarization curves are the most common tool for evaluating the performance of reversible solid-state oxidation batteries and represent the relationship between current density and battery operating voltage. This curve can reveal the sources of performance loss of rSOC under different operating conditions, such as activation loss, ohmic loss and concentration loss. The sum of these three losses forms an indicator called overpotential.
Interestingly, the open circuit voltage (OCV) is the same even in SOFC and SOEC modes as long as the gas composition of the reactants is the same.
Reversible solid-state oxidation cells can handle a variety of different reactants during operation, such as the conversion of hydrogen and its form, as well as the use of carbon-based reactants. This makes rSOC particularly unique among relatively low-temperature battery technologies. For example, when using hydrogen and water vapor to perform an electrochemical reaction, the forward reaction is the oxidation of hydrogen, while the reverse reaction is the reduction of water.
In SOFC mode, the oxidation reaction of hydrogen produces water and electrons; in SOEC mode, water is reduced back to hydrogen.
Because rSOC can effectively operate at high temperatures, it exhibits more advantages over traditional technologies such as pumped hydro and compressed air energy storage in seasonal energy storage. These technologies are often geographically restricted, and lithium-ion batteries have limited discharge capabilities. The emergence of hydrogen storage technology provides the possibility of long-term storage, because the produced hydrogen can be compressed and stored for several months.
rSOC not only improves efficiency, but also enables the charging and discharging processes to be performed on the same device, which is more economically feasible.
With the vigorous development of renewable energy, the maturity and application of rSOC technology will become an important part of the future energy field. This not only relies on continuous technological innovation, but also requires the joint efforts of consumers and industry. In the future, can we make full use of this technology to promote the process of global sustainable development while balancing energy supply and demand?