Sustainability is often described in shades of green, but the future of clean energy may also carry a hint of deep blue. Electric vehicles and energy storage systems could soon draw power from a familiar pigment found in denim.
Concordia researchers have found that indigo, the natural dye used to colour fabrics for centuries, can help shape the future of safe and sustainable batteries. In a study published in Nature Communications, the team shared that the common substance supports two essential reactions inside a solid-state battery at the same time. This behaviour helps the battery hold more energy, cycle reliably and perform well even in cold conditions.
"We were excited to see that a natural molecule could guide the battery chemistry instead of disrupting it," says Xia Li, the study's lead author and associate professor in the Department of Chemical and Materials Engineering. "Indigo helps the battery work in a very steady and predictable way. That is important if we want greener materials to play a role in future energy systems."
From left: Professor Xia Li and first author of the study, Qihang Yu.A carefully managed reaction
Solid-state batteries use solid material instead of liquid to move lithium ions. They are safer and have the potential to store more energy, but they have a long-standing challenge. Organic materials are a greener and more affordable option, but they usually do not mix well with the solid ingredients inside these batteries. When they interact too much, the battery becomes unstable. Because of this, most researchers look for ways to stop that reaction.
This study reveals that, when carefully managed, the reaction between indigo and the electrolyte can improve the battery's performance.
The team found that indigo stores and releases lithium while gently activating the solid electrolyte so it can store energy as well. This cooperation between the dye and the electrolyte boosts the overall capacity far beyond what either material could deliver alone.
It also allows the battery to operate smoothly at room temperature and even at minus ten degrees Celsius.
Refinement needed for practical application
Achieving such high capacity and such stable cycling in cold conditions is extremely rare for solid-state batteries that rely on organic materials.
"Our study represents one of the strongest performances reported for this battery type," Qihang Yu says, the first author of the study. "It suggests that natural molecules like indigo can help overcome long-standing compatibility challenges and support more accessible and sustainable battery technologies."
Li adds that the next phase of the work will focus on pushing the technology closer to real-world use. The goal is to refine the reactions inside the battery so it can remain stable while storing much larger amounts of energy in a small area. That would bring organic-based, solid-state batteries much closer to practical applications.
Learn more about research at Concordia's Gina Cody School of Engineering and Computer Science.
