Development of ‘Solid-State Power Storage System’ by Mimicking Power Generation Principles of Electric Eels
Drawing Attention as Future Renewable Energy Source Through Engineering-Electrochemistry Convergence Research
Professor Suk-Won Hwang’s group published the paper in Advanced Functional Materials

▲ (From left) Dr. Won-bae Han (first author/KU-KIST Graduate School of Converging Science and Technology), Dong-je Kim (master, first author/Samsung Electronics Semiconductor Research Institute), Yong-min Kim (first author/doctoral student in the Department of Chemical Engineering at University of Seoul), Professor Suk-won Hwang (corresponding author/KU-KIST Graduate School of Converging Science and Technology), and Professor Hong-chul Moon (corresponding author/Department of Chemical Engineering at University of Seoul).

A research team consisting of Professor Suk-won Hwang’s group at the KU-KIST Graduate School of Converging Science and Technology and Professor Hong-chul Moon’s group at the University of Seoul developed a flexible solid-state energy storage system by mimicking the power generation principles of electric eels. 

Electric eels have their essential organs at their head end, and their body is mostly composed of special cells that are referred to as electrocytes. Numerous sodium and potassium ion channels are present at both ends of these electrocytes, and nerve stimulation triggers the opening or closing of the channels, creating an ion concentration difference between the inside and the outside of the cells. At that time, an electric polarization develops, generating a potential difference. Since numerous electrocytes are connected in series or stacked in parallel, electric eels can create a temporary voltage as high as up to 800 V for hunting or self-defense. Mimicking the power generation principles of electric eels may help develop an eco-friendly renewable energy source for the generation electric power based on only the migration of ions.

The researchers have successfully developed artificial electrocytes mimicking the power generation principles of electric eels based on osmotic ion flows and electrostatic ion interactions. The artificial electrocytes consist of a high-concentration ion gel, a low-concentration ion gel, and polymer membranes of cationic chains and anionic chains disposed between these two ion gels. When ions migrate between the ion gels due to an osmotic pressure difference, the cation polymer membrane selectively allows only the anions to pass and the anionic polymer membrane allows only the cations to pass. The resulting charge imbalance created electric polarization, producing a voltage of about 140 mV.

These electrocytes, incorporating components featuring excellent mechanical properties and thermal stability, were capable of stably generating a voltage even under repeated deformations such as bending and twisting, and they maintained their power generation behavior across a temperature range of -20 °C to 100 °C without becoming frozen or burned.

Furthermore, the researchers connected the electrocytes in series and in parallel to achieve a maximum voltage of 22 V, thereby presenting the potential for large-area, high-voltage power generation. They also fabricated a system in which all the ion gels and polymer membranes are separated, providing a strategy for generating electric power when needed through a simple origami folding method.

Professor Suk-won Hwang (KU-KIST Graduate School of Converging Science and Technology) said, “Through this study, we developed an electric eel-inspired artificial electrocyte-based energy storage system using the convergence of engineering technologies and electrochemical research to implement soft electronic devices.” He added, “We expect that our system can be utilized as a sustainable next-generation renewable energy source applied to a range of environments where system operation is required under high-voltage, cryogenic or high-temperature conditions.”

The research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (the Ministry of Science and ICT, MSIT), the development of technologies for electroceuticals of the National Research Foundation (NRF) funded by the Korean government (MSIT), and ICT Creative Consilience program supervised by the IITP (Institute for Information & Communications Technology Planning & Evaluation). The results were published online in Advanced Functional Materials (IF=19.9), a globally renowned journal, on October 2, 2023.
* Title of article : Electric Eel-Inspired Soft Electrocytes for Solid-State Power Systems

* Name of journal : Advanced Functional Materials (Adv. Funct. Mater. 2023, doi/10.1002/adfm.202309781)

<Figure 1>

1. The power generation mechanism of electric eels in which a high voltage may be formed by the electric polarization caused by the opening and closing of ion channel proteins. .

2. The energy storage system in this research in which the artificial electrocytes are connected both in series and in parallel. When ions migrate between the ion gels due to an osmotic pressure difference, the cation polymer membrane selectively allows only the anions to pass and the anionic polymer membrane allows only the cations to pass. The resulting charge imbalance creates an electric polarization, which was able to produce a potential difference of about 140 mV..

3. An energy storage system in which 165 artificial electrocytes are connected in series and the linear voltage behavior depending on the discharge of the energy storage system and the number of artificial electrocytes..