Nicknamed the ‘Methuselah quinone’ - after the longest-lived Biblical figure - the researchers believe this molecule could usefully store and release energy many tens of thousands of times over multi-year periods.
"We designed and built a new organic compound that can store electrical energy and also has a very long life before it decomposes," claims Professor Roy Gordon of Harvard. "We discovered degradation processes of the molecules that we previously used in flow batteries. Then we created new, more stable molecules that avoid these problems."
"In previous work, we had demonstrated a chemistry with a long lifespan but low voltage, which leads to low energy storage per molecule, which leads to high cost for a given amount of energy stored," adds Michael Aziz of Harvard. "Now, we have the first chemistry that has both long-term stability and comes in at more than one volt, which is commonly considered the threshold for commercial deployment. I believe it is the first organic-based flow battery that meets all of the technical criteria for practical implementation."
The Methuselah molecule is a modified quinone, an abundant, naturally occurring molecule integral to biological processes like photosynthesis and cellular respiration. The research team explains that they characterised the degradation process of previous quinone molecules in flow batteries and made modifications to increase the calendar life.
In experiments, the Methuselah molecule had a fade rate of less than 0.01% per day and less than 0.001% per charge/discharge cycle—which extrapolates to less than 3% degradation over the course of a year—and useful operation for tens of thousands of cycles.
Methuselah also proved highly soluble, the researchers add, meaning it can store more energy in a smaller space. It operates in a weak alkaline electrolyte, reducing the cost of the battery by allowing the use of inexpensive containment materials and an inexpensive polymer membrane to separate the positive and negative terminals.
The hope is that organic molecules will be a viable, long-lasting, cost-effective alternative to expensive vanadium batteries. The researchers are now seeking commercial partners to scale up the technology for industrial applications.
