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The secrets of reversible solid-state oxide batteries: How do they charge and discharge simultaneously?
With the increasing global demand for renewable energy and high-efficiency energy storage technologies, reversible solid-state oxide batteries (rSOCs) have become an attractive research area. This emerging technology is not only able to operate as a solid-state oxidation fuel cell, but can also be transformed into a solid-state electrolyzer, which helps improve the efficiency of energy storage and conversion. This article will take a closer look at the structure, working principle, and potential of rSOC for energy storage.
A reversible solid-state oxidation cell is a solid-state electrochemical device that can operate alternately between solid-state oxidation fuel cell and solid-state electrolyzer modes.
Technical description
Battery structure and working principle
The rSOC system consists of four main components: electrolyte, fuel and oxygen electrodes, and interconnect components. The porous layers of these electrodes facilitate the diffusion of reactants within them and catalyze electrochemical reactions. In conventional technologies such as SOFCs and SOECs, the electrodes each have a single function, but in reversible solid-state oxidation cells, both modes can be alternated in the same device. This allows more general names to be used when describing the electrodes, such as fuel electrode and oxygen electrode.
In SOFC mode, the oxidation reaction of the fuel occurs at the fuel electrode, while in SOEC mode, it is the reduction reaction of oxygen ions. On the oxygen electrode, the oxygen reduction reaction takes place in SOFC mode and the oxidation reaction in SOEC mode. When the rSOC operates in SOFC mode, oxygen ions flow from the oxygen electrode to the fuel electrode, where oxidation reactions occur; while in SOEC mode, the reactants are reduced at the anode and produce oxygen ions, which again flow to the oxygen electrode.
Polarization Curve
A common tool for evaluating rSOC performance is the polarization curve. This graph shows the relationship between the current density of a battery and its operating voltage. When the rSOC circuit is not closed, the operating voltage is called the open circuit voltage. When a certain fluctuation or current is extracted or supplied, the operating voltage will start to deviate from the open circuit voltage, which is mainly affected by activation losses, ohmic losses and concentration losses.
Chemical reactionsIn SOEC mode, if the operating voltage is less than the thermoneutral voltage, the reaction is endothermic; if it is greater than the thermoneutral voltage, it is exothermic.
In the operation of rSOC, the reaction between hydrogen and water vapor is a common chemical reaction. In SOFC mode, hydrogen reacts with oxygen to form water, while in SOEC mode, water is decomposed back into hydrogen and oxygen.
In addition, rSOC is not limited to hydrogen reactions but can also process carbon-containing reactants such as methane. These chemical reactions can be carried out at high temperatures with reduced risk of catalyst poisoning, providing more flexible options for energy conversion.
Ammonia is a potential hydrogen carrier, as its high volumetric density enables it to be used as an efficient fuel.
rSOC system and its application in energy storage
rSOC has attracted increasing attention due to its excellent performance, especially in periodic or seasonal energy storage. Compared with traditional pumped storage and compressed air energy storage technologies, rSOC systems have significant advantages in terms of lack of geographical restrictions and higher energy storage density.
In this scenario, hydrogen storage becomes an ideal choice. rSOC can perform bidirectional operations in power generation and hydrogen conversion. Such high efficiency not only reduces the overall investment cost of the equipment, but also enhances the stability of the system.
Circuit efficiency
When discussing rSOC, loop efficiency is a very important indicator, which represents the efficiency of the energy conversion process from charging to discharging. As battery performance improves, this parameter will become an important factor in determining rSOC's competitiveness in the market.
The loop efficiency of rSOC can be used as an important indicator to evaluate its effectiveness in energy conversion.
As the demand for renewable energy technologies continues to increase, could reversible solid-state oxide batteries become a mainstream solution for energy storage in the future?
