Scientists in Sweden are stepping up in the global race to efficiently store renewable energy with an all-organic proton battery whose capabilities surprised even the researchers. Among them, the battery can be recharged directly from a solar cell within seconds, and can withstand temperatures of up to -24 degrees Celsius without losing capacity.
The path to market remains long, but easier disposal compared to the hazardous-waste disposal challenges surrounding lead-acid and lithium-ion batteries could also provide a competitive advantage in the rapidly expanding energy-storage market, analysts say. Globally, energy storage is projected to grow to $546 billion in annual revenue and 3,046 GWh in annual deployments by 2035.
"If there are advantages of easier disposal, that could be a competitive advantage," especially if it showed up in lower overall costs, California Energy Storage Alliance executive director Alex Morris said.
The global storage market is growing so fast that it needs innovation across technologies, said Matthew Raiford, manager of the Consortium for Battery Innovation. The consortium funds lead-acid battery research but welcomes organic batteries like these, he said. "There will be many ways for lithium, for lead, for zinc, and eventually for organic batteries, once they mature, to provide this utility to our society."
'Surprising' resilience to cold
The new organic proton battery was developed at Uppsala University by a team led by Christian Strietzel, who spent more than two years on the project. The results were published this spring in the scientific journal Angewandte Chemie.
The team used naturally occurring quinones (which can be synthetically produced or found in bacteria, fungi and some higher plant forms), placing them in an acidic aqueous electrolyte solution. Previous researchers had developed batteries from organic materials, but their smaller molecules tended to dissolve more easily into the electrolyte, making the batteries less stable long-term.
Currently, lead-acid and lithium-ion batteries dominate the global market. The older lead-acid model is widely used in automotive and industrial settings, while lithium-ion batteries make up more than 90% of the global grid battery storage market.
Lead-acid batteries, which can operate at very low temperatures, provided the Swedish research team some inspiration, but those batteries can lose half their capacity when going from 20C to -20C.
The surprise with the new proton battery was that it remained stable even at temperatures far below freezing, Strietzel told Utility Dive. "We knew you could go low with the electrolyte, but we anticipated it would have some effect on the performance," he said. "It was surprising that it wouldn't have an effect on the capacity. We were expecting to lose up to 90% of the capacity."
The researchers believe that imperviousness to ambient temperature could allow interesting applications, like permitting a storage facility in a cold location to forgo heat.
A lithium-ion battery requires a charge controller to monitor the charge. The organic proton battery can recharge directly from a solar cell without electronics — which opens up the possibility of buying a solar cell that has a battery integrated, Strietzel said. "During the day it's the solar cell; at night it's the battery," he says. "This is where it could be interesting and enable renewable technologies."
Its energy density is comparable to lead-acid batteries, making it suitable for future applications where weight is not of paramount concern. It would not be ideal for vehicles, the researchers said, but could work well for grid storage, small sensors, and smart-home applications.
They also plan to work to make such batteries 3D-printable. Currently the organic battery is cased like a standard cylinder, but in order to be printed they might be flattened and developed into different shapes.
Battery lifespan unknown
What remains to be seen is an organic proton battery's potential lifespan. The Swedish team's prototype can be rapidly recharged more than 500 times without degrading its efficiency, but that number is much lower than other battery types.
Lithium-ion batteries have a cycle life — the number of times a battery can be charged and discharged — of 2,500 to 4,000. Lead-acid batteries have a cycle life of 1,000 to 5,000, and the Consortium for Battery Innovation has recently pushed for research into increasing their efficiency, hoping to make them a more economic storage technology that can back up renewable energy.
Another key question is how economically such batteries could be produced. Organic batteries do not require mined metals, which could eventually provide a market advantage. Lead is plentiful and produced in the U.S., while lithium-ion materials are often procured from China and elsewhere.
Safety concerns, including end-of-life disposal, have also dogged lithium-ion batteries as the energy industry weighs utility-scale battery storage. The nontoxic organic model would avoid those issues.
While quinones can be synthetically produced at modest cost, the economies of scale that are critical in the chemical industry would be critical to making organic proton batteries commercially viable, Strietzel said. "It's like the cooking process," he said. "The ingredients can be abundant and cheap, but putting them together isn't necessarily simple. We're looking at partnering up to make these commercialized and make these cheap."
Raiford called the research a "very intriguing possibility" and praised the researchers for using relatively popular organic semiconductor materials, which could make production more practical.
"For organic batteries in general one of the major hurdles is to make sure you use streamlined and practical synthetic routes. That's a strength of this paper," he said. "Regardless of typical batteries used now, inorganic batteries have challenges, and organic batteries help with those challenges."