Can light offer a better way to make energy-storage materials?

Istanbul, Türkiye – Many technologies, such as electric vehicles recovering energy during braking and electronic devices needing sudden power bursts, require rapid energy storage and release. Supercapacitors are designed for this purpose. Unlike batteries, which store larger energy quantities over time, supercapacitors can quickly charge and discharge and are durable through repeated cycles.

Improving their storage capacity is only part of the challenge. Researchers are also developing better manufacturing methods for their internal materials. A team led by scientists at Istanbul Technical University has pioneered an innovative approach: using light to synthesize the energy-storing material itself. The team used ultraviolet light to create a conductive polymer called PEDOT directly around polydopamine (PDA), a bio-inspired polymer known for surface adhesion. The resulting composite outperformed PDA alone and a comparable PEDOT electrode in charge storage, retaining 91% of its initial capacitance after 2,000 charge-discharge cycles.

Published in Reactive and Functional Polymers, this study indicates that light-driven polymerization could offer a new manufacturing route for future energy-storage materials.

Changing how the material is made

PEDOT, short for poly(3,4-ethylenedioxythiophene), is a widely studied conductive polymer for supercapacitors. Its electrical conductivity makes it ideal for rapid charge transfer, but it faces challenges like poor adhesion, mechanical instability, and ion transport issues. To overcome these limitations, researchers combined PEDOT with polydopamine (PDA). Inspired by mussel adhesive chemistry, PDA has functional groups that interact with surfaces and electrolytes, enhancing ion movement between the electrode and electrolyte. Although PEDOT and PDA are known materials, previous uses primarily involved electrochemical polymerization or their combination with other conductive materials. The researchers adopted a different approach, employing light to initiate polymer formation and grow PEDOT around PDA.

"The key difference isn’t just the materials, since PEDOT and polydopamine are established. Our goal was to see whether light could enable a new way to assemble them, forming conductive PEDOT directly around PDA under mild conditions,” explained Kerem Kaya from the Chemistry Department at Istanbul Technical University.

This team reports the inaugural in-situ photopolymerization of the PDA–PEDOT composite, extending previous research demonstrating that both PEDOT and dopamine can be formed through light-induced polymerization.

Letting light start the process

The researchers combined the starting materials for PDA and PEDOT with phenacyl bromide, functioning as a photoinitiator, using ethanol as the primary solvent. They then irradiated the mixture with ultraviolet-A light, which activates the photoinitiator to produce reactive species that trigger polymerization. Their experiments indicate that PDA forms first, followed by PEDOT, resulting in a coated structure. Microscopy revealed changes in thickness and surface features consistent with PEDOT encasing PDA. Elemental mapping confirmed sulfur, an indicator of PEDOT, distributed across the PDA surface, supporting the presence of the coating. Light offers an additional advantage by enabling control over the timing and location of polymerization. The researchers successfully coated various surfaces, including metal, steel, and resin, suggesting potential applications in fabricating energy-storage materials directly on specific structures.

Two materials doing different jobs

Using a combination of the two polymers altered the material's charge storage efficiency. PEDOT creates a conductive network that facilitates electron flow within the electrode, while PDA offers chemical groups that interact with ions in the electrolyte, enabling reversible reactions. The complementary functions of these polymers enhance the movement of both ions and electrons through the composite.

"The two polymers complement each other. PEDOT provides electrical conductivity, while polydopamine helps the electrode interact with the electrolyte and provides additional sites for charge storage. By bringing these properties together, we can improve how effectively the material stores and moves charge,” explained Baris Kiskan from Istanbul Technical University’s Chemistry Department.

From shining light in the laboratory to storing energy in the real world

The findings do not imply that light-based supercapacitors are ready for use in electric vehicles or electronics. The researchers tested the material as an electrode within a laboratory three-electrode system rather than as a full commercial supercapacitor. Further research is necessary to evaluate its performance in complete devices, durability under real-world conditions, and scalability of the light-driven process for manufacturing.

Practical questions also remain, such as the current polymerization process requiring 24 hours of UV irradiation. Optimizing reaction time, energy consumption, and production scale will be crucial before considering this method as an industrial option. Nonetheless, the study highlights a broader potential in energy-storage research: better devices may result not just from discovering new materials but also from improving how we assemble existing ones.

"When we think about improving energy storage, we often focus on discovering a new material. Our work shows that how we make and organize existing materials can be just as important. Light offers an additional way to control this process, potentially opening new avenues for designing future energy-storage electrodes," said Kerem Kaya.

Consumers' main goal is clear: to have technologies that rapidly store energy, deliver it on demand, and last through many cycles. Reaching this goal will demand improvements in all parts of an energy-storage device, from chemistry to production. This research suggests that light might play a crucial role in developing these components.