Researchers have developed a new model that helps explain how electric double layers (EDLs) store energy in supercapacitors, paving the way for more efficient energy storage in devices like portable electronics and electric vehicles.
This model can predict how well a supercapacitor can store electric charge, and its results closely match experimental findings. The study was published in ChemPhysChem.
Supercapacitors are different from traditional batteries. While batteries release energy steadily over a long period, supercapacitors deliver short, powerful bursts of energy.
For example, a battery can be compared to a jar that stores energy slowly and releases it gradually, while a supercapacitor is like a bucket that fills and empties quickly.
This makes supercapacitors ideal for situations where quick energy delivery is needed, such as in cars and emergency power systems.
The key to a supercapacitor’s performance is the electric double layer (EDL), a thin layer at the interface between the electrode and an electrolyte solution.
This layer is where energy is stored. The ability of a supercapacitor to store charge depends on factors like the surface area of its electrodes, the distance between them, and the type of material used in the electrolyte layer, which is only a few nanometers thick.
Because of these properties, supercapacitors can store much more energy than traditional capacitors.
However, understanding and improving the EDL requires examining chemical interactions at a very small scale, which is difficult to do with experiments alone. This is where the new model comes in.
Scientists from HSE MIEM and the Semenov Research Centre of Chemical Physics have created a model to better describe what happens in the EDL. They used a modified version of the Poisson-Boltzmann equation, which takes into account the complex interactions between ions, water molecules, and the electric field.
The model provides detailed predictions of how the EDL’s ability to store charge changes as the voltage varies. This is measured through differential electrical capacitance, which tells us how much charge the EDL can hold with small voltage changes. The higher the differential capacitance, the better the supercapacitor can store energy.
The study focused on two types of electrolyte solutions, sodium perchlorate (NaClO4) and potassium hexafluorophosphate (KPF6), interacting with a silver electrode. The model accurately predicted the structure of the EDL and the capacitance behavior at different concentrations of these solutions. The model was also able to predict the behavior of more complex mixtures of these electrolytes, making it useful for a wide range of electrochemical systems.
This model is an important step toward designing better supercapacitors. By predicting how the EDL behaves in real-world conditions, it will help scientists develop new energy storage devices that are more efficient and powerful, benefiting everything from portable gadgets to electric vehicles.
Future research aims to improve the model further by including systems with stronger interactions between ions and electrodes, which are common in modern devices.
