March 14, 2020 by Luke James
Researchers from York University in Canada have come one step closer to creating an organic battery that can last longer than conventional batteries and is also better for the environment.
With organic batteries, toxic metals and chemicals are replaced with environmentally friendly, organic materials that take on the role of an electrode. While previous research into organic batteries has primarily focused on protein-based solutions, York University’s study highlights a carbon-based organic molecule instead.
The research, which was published in the journal Batteries & Supercaps, spells out the research team’s goal—to replace metals such as cobalt in widely-used lithium-ion batteries.
York University's Thomas Baumgartner in his lab. The scientist leading a team of researchers in developing and testing new molecules to replace rare metals that are prominently used. Image Credit: York University.
Organic electrodes—experimental ones, at least—already exist. They are made from elements like carbon, nitrogen, oxygen, phosphorus, and sulphur. However, they all deteriorate on a cycle-by-cycle basis through red-ox reactions. Over time, these red-ox reactions gradually dissolve into the electrolyte and cause low conductivity and terminal voltage.
As Professor Thomas Baumgartner from York University highlights in the research paper, the problem with current organic battery research is that “…[it generally] uses the same very few organic building blocks as active component” and added that for the technology to develop, new electroactive molecules are required. This is exactly what Baumgartner’s team are doing—its goal is to “develop new building blocks”
During their study, the researchers used an electroactive chemical compound called phosphoryl-bridged viologens (“phosphaviologens”) tethered to a carbon nanotube. This created an organic body that can replicate the metals commonly found in a typical lithium-ion battery.
At the testing phase, a peak voltage of 3.5 volts was observed, even after 500 battery cycles. In contrast, a typical lithium-ion battery will have long since started to degrade by the time it goes through a similar number of charge cycles.
Viologen was chosen because it is a known electron acceptor that can give up not one but two electrons without causing damage—providing higher storage capacity.
It is important to note that the fundamental nature of batteries will not change—an organic battery will still be a lithium-ion battery at its core. Only the building blocks of the electrodes will be changed, to a more organic and environmentally friendly compound.
This technology also isn’t ready yet. There are still plenty of shortcomings that the research team must tackle, including a significant capacity loss at lower temperatures of around 5 degrees Celcius. The battery is also much heavier when compared to current lithium-ion batteries, a clear step in the wrong direction if it is ever to be used in consumer products like smartphones and wearables.
Baumgartner said, “Many molecules are still too heavy for the amount of energy that can be stored in a given volume. That is what we are working on – making the materials better in storing more energy by also becoming lighter.”
He also acknowledged that organic batteries “continues to be a maturing field” but that he and his team—which is currently developing the next generation of molecules that show promise in being able to increase current capacity—is hopeful for the future.
