The new study shatters conventional wisdom and opens up a future for electrochemical devices

(Nanowerk News) A new study by researchers at the University of Cambridge reveals a surprising discovery that could change the future of electrochemical devices. These findings offer new opportunities for the development of advanced materials and performance enhancements in areas such as energy storage, brain-like computing and bioelectronics.

Electrochemical devices rely on the movement of charged particles, both ions and electrons, to function properly. However, understanding how these charged particles move together has presented a significant challenge, hindering progress in creating new materials for these devices.

In the fast-growing field of bioelectronics, soft conductive materials known as conjugated polymers are used to develop medical devices that can be used outside of traditional clinical settings. For example, this type of material could be used to make wearable sensors to remotely monitor a patient’s health or implantable devices that actively treat disease.

The biggest benefit of using conjugated polymer electrodes for this type of device is their ability to seamlessly combine ions, which are responsible for electrical signals in the brain and body, with electrons, carriers of electrical signals in electronic devices. This synergy enhances the connection between the brain and the medical device, effectively translating between these two types of signals.

In a recent study on conjugated polymer electrodes, published in Natural Ingredients (“hole-limited electrochemical doping in conjugated polymers”), researchers reported an unexpected finding. It is conventionally believed that the movement of the ions is the slowest part of the charging process because they are heavier than the electrons. However, this research reveals that in conjugated polymer electrodes, the movement of “holes” — empty spaces for electrons to move through — can be a limiting factor in how fast the material fills up.

Using a special microscope, the researchers closely observed the charging process in real time, and found that when the charging rate was low, the movement of the holes was inefficient, causing the charging process to be slower than expected. In other words, and contrary to standard knowledge, the ions move faster than the electrons in this particular material.

This unexpected finding provides valuable insight into the factors that affect charging speed. Interestingly, the research team also determined that by manipulating the microscopic structure of the material, it is possible to regulate how fast the holes move during filling. This newfound control and ability to fine-tune material structure allows scientists to engineer conjugated polymers with better performance, enabling faster and more efficient filling processes.

“Our findings challenge conventional understanding of the charging process in electrochemical devices,” said first author Scott Keene, from Cambridge’s Cavendish Laboratory and Electrical Engineering Division. “The movement of holes, which serve as empty space for electrons to move around, can become very inefficient during low levels of charge, causing unexpected slowdowns.”

The implications of these findings are far-reaching, offering promising avenues for future research and development in the field of electrochemical devices for applications such as bioelectronics, energy storage, and brain-like computing.

“This work addresses a long-standing problem in organic electronics by illuminating the basic steps that occur during the electrochemical doping of conjugated polymers and highlighting the role of polymer band structures,” said George Malliaras, senior author of the study and Prince Philip Professor of Technology in the Department of Engineering’s Division of Electrical Engineering.

“With a deeper understanding of the charging process, we are now able to explore new possibilities in manufacturing state-of-the-art medical devices that can integrate seamlessly with the human body, wearable technologies that provide real-time health monitoring, and new energy storage solutions with increased efficiency, concluded Prof. Akshay Rao, senior co-author, also from Cambridge’s Cavendish Laboratory.