Batteries ‘as big as you want’? Research offers clues

Source: By Parker M. Shea, E&E News reporter • Posted: Tuesday, March 3, 2020

Scientists are one step closer to understanding why organic flow batteries — touted as a potential bridge to utility-scale energy storage — break down so quickly.

Researchers at the University of Cambridge have for the first time applied magnetic resonance imaging to view the inner chemical workings of redox flow batteries, an alternative to the older lithium-ion technology that currently dominates the battery storage market. The process could be used to better understand and extend the technology’s life span, according to a paper published yesterday in Nature.

“Redox flow batteries are useful because you can make them as big as you want. Normally, if you have a battery, its energy density is contained by how big the box is that it’s contained in,” said Cambridge professor Clare Grey, who leads the research group behind the paper.

Lithium batteries face trouble at large scales due to flammability and other problems (Climatewire, Jan. 29). Redox flow technology, by contrast, is “inherently scalable,” Grey said — but the batteries deteriorate too fast to be useful.

Using its new tools for near real-time visibility, Grey’s team found that by charging redox flow batteries at a lower voltage, it’s possible to slow the decay of critical compounds.

“Since the organic molecules tend to break down quickly, it means that most batteries using them as electrolytes won’t last very long, making them unsuitable for commercial applications,” said Cambridge professor Evan Wenbo Zhao, who was the paper’s lead author. “While we’ve known this for a while, what we haven’t always understood is why this is happening.”

Zhao’s findings are one of many recent advancements that bring redox flow batteries closer to large-scale viability. Market analysts, however, are skeptical the technology could dethrone lithium-ion batteries, which accounted for up to 95% of the global stationary energy storage technology market in 2018, according to Wood Mackenzie.

The market analysis firm attributes this success to lithium-ion’s pervasiveness across scales ranging from electronic cigarettes to electric vehicles to solar farms. The last 10 years saw the cost of lithium-ion batteries drop by 85%, according to Wood Mackenzie, and the firm said it expects prices will continue to drop an average of 9% per year until 2026.

But lithium-ion storage has its limits.

“While well suited to help with second-to-second system balancing, renewables ramping, and providing peak power services, for longer storage durations, we’re going to need more than lithium-ion technologies,” Rory McCarthy, Wood Mackenzie’s principal analyst for energy storage, wrote last year.

Grey said that although redox flow batteries can’t yet compete with lithium-ion, they will have to become viable in the future as demand for long-term storage grows. She sees her team’s work in the fundamental science of the batteries as a crucial first step toward making the necessary technological progress possible.

“The challenge for academics like me is: How do we come up with the massive electric storage?” she said. “We need something that is inherently bigger, and lithium-ion is not going to be suited for that. Ultimately, we’re going to have to do it with some kind of chemical storage. And [redox flow battery technology] is one option.”