Although lithium-ion batteries are the most commonly used energy storage technology—powering cell phones, cars, and the electrical grid—the technology has limitations. The lifespan of lithium-ion batteries is relatively short. Furthermore, they can be challenging to recycle. Researchers today are working to develop new chemistries that will provide a non-toxic, non-corrosive option that last longer than lithium-ion batteries—estimated at a decade rather than months.
Flow batteries store energy in liquid solutions. But after many charge-discharge cycles the electrolyte needs to be refreshed in order to restore the battery’s storage capacity. Researchers at Harvard University, led by Michael Aziz and Roy Gordon recently announced that they were able to successfully modify the molecular structure of both ferrocene and viologen, the positive and negative electrolyte solutions, to develop a water-soluble flow battery with a lifespan of nearly ten years.
The new battery relies on the molecule viologen as the negative electrolyte, and the molecule ferrocene for the positive electrolyte. In order to utilize these molecules, the researchers had to first modify their molecular structure to make them water-soluble and more resistant to degradation.
The team successfully created a new flow battery that stores energy in organic molecules dissolved in neutral pH water and loses just one percent of its capacity every 1,000 cycles, according to New Atlas. “Lithium ion batteries don’t even survive 1000 complete charge/discharge cycles,” said Aziz in a press release. Though the primary target is grid-scale energy storage, this new iteration of flow batteries requires minimal maintenance and would be as safe for home use as any other large appliance.
Researchers are aiming to accomplish a US Department of Energy goal to create a battery that can store energy for less than $100 per kilowatt-hour, which would make stored energy competitive with traditional power plants. “If you can get anywhere near this cost target then you can change the world,” said Aziz. “It becomes cost effective to put batteries in so many places. This research puts us one step closer to reaching that target.”
“Aqueous soluble ferrocenes represent a whole new class of molecules for flow batteries,” said Aziz in a Harvard University press release. The neutral make-up of the solution should also lower the cost of the membrane needed to separate the two sides of the battery, while also making it less toxic. Harvard has filed patents related to the breakthrough for “innovations in flow battery technology.”
The research was coauthored by Diana De Porcellinis, Rebecca Gracia, and Kay Xia. It was supported by the Office of Electricity Delivery and Energy Reliability of the DOE and by the DOE’s Advanced Research Projects Agency-Energy.
What applications beyond grid-scale energy storage do you envision for this technology?