Michigan Researchers Seek New Chemistries to Diversify Rechargeable Battery Applications

Author: Jimmy Brancho

Editors: Irene Park and David Mertz

Off the Danish coast in Copenhagen, Don Siegel, an associate professor in the University of Michigan’s College of Engineering, is on sabbatical. He said the ocean is speckled with tall, white windmills. At some sites, they stand in great curving rows; at others, they’re arrayed in a geometrical pattern.

“Denmark’s very windy,” he said over the phone.

He’s right. The country, according to Energinet, receives 42 percent of its electrical power from wind alone. In fact, Siegel said sometimes there are “emergency situations” where the turbines are pumping out electricity faster than it can be used.

“If we had extra energy storage, imagine what we could do with that,” he said.

Surprisingly, the cell phone battery in your pocket might hold the solution for the excess electricity in the Danish wind farms. Charging a battery is a convenient and stable way to store energy from intermittent sources like wind and solar farms. Rechargeable batteries are being worked into strategies to make renewable energy more reliable in addition to building new devices like laptops and electrified cars.

New battery technology is designed with one of three main areas in mind. First comes consumer electronics — the lightweight laptops and cellphones that we use every day. Second are electric vehicles, including both hybrid electric vehicles and fully electric vehicles. Finally, engineers have proposed massive, immobile rechargeable batteries that could be used to store energy from intermittent renewable sources like wind and sunlight. This idea is referred to as grid storage. Each of these three uses of batteries poses a different set of design criteria, challenges, and potential problems.

Current Battery Technology: Lithium-Ion and Beyond

Lithium-ion batteries, from their beginnings in the 1980s, have been a staple of the consumer electronics industry, used in every cell phone and laptop computer. The reliable and relatively safe energy offered by a conventional lithium-ion battery has made them part of a $30 million market that is projected to grow to over $77 billion by 2024, according to Transparency Market Research.

However, the role of the lithium-ion battery might change significantly before 2019 as scientists are constantly researching new ways to make the batteries cheaper, safer, and more powerful.

“Lithium-ion has gotten a lot cheaper over the last decade,” said Siegel, whose lab is also part of the University of Michigan Energy Institute (UMEI). “It’s really sort of shocking how much the price has come down.”

Greg Less, Senior Laboratory Manager at the UMEI Battery Fabrication and User Facility, said he thinks the future of energy storage could involve a variety of different technologies. He said the Earth doesn’t have very much lithium left and concerns over running out are real.

As Nature magazine addressed in a battery-themed outlook issue in October 2015, lithium-ion batteries might be nearing the limit of what’s possible. If researchers want companies to use batteries to store renewable energy and build affordable electric vehicles, they need the batteries to be better – perhaps cheaper, faster, and more stable than lithium-ion can provide.

“We need other chemistries for other applications,” says Gülin Vardar, a University alumna who earned her Ph.D. studying the chemistry of advanced batteries.

“I think we need to be judicious in where we use lithium-ion and recycle as much as we can,” Less said. “For a large stationary power bank, it makes more sense to use a heavy, stable technology that isn’t applicable to vehicles or portable electronics.”

Some of the proposed alternatives to lithium-ion don’t look all that different. Vardar’s thesis project focused on magnesium-ion batteries. Magnesium, 1,700 times more abundant than lithium, also carries double the charge, which theoretically means that a magnesium-ion battery can pack more energy into the same weight and size.

But because of their higher charge, magnesium ions move more slowly toward battery electrodes. Since the ion flow toward electrodes is crucial for a battery to function, the slow-moving ions pose a challenge.

“That’s the advantage and also the disadvantage,” Vardar said, “because the ion does not want to move.”

Siegel’s lab also researches technologies beyond lithium — like lithium-air and lithium-sulfur batteries, in which energy is stored and released in sync with reversible chemical reactions between lithium and oxygen or sulfur, respectively.

“We mostly focus on batteries that don’t work,” he said. “If we can figure out why they don’t work and use that to get targeted improvements, we might be onto something.”

Future of Battery Research at the University

The University of Michigan is uniquely poised to make strides in battery research with the recent opening of the battery fabrication facility. Less, who oversees this lab, said their research allows greater access for people to study battery technology.

“The reason that the Battery Lab is important and is going to help Michigan do great things is that batteries behave differently at the laboratory scale than they do at the production scale,” he said.

Scientists researching new battery materials make a handful of small test batteries. The machinery at the Battery Lab allows researchers to study thousands of batteries at a time in different assembly configurations to get an idea of how real consumer products might perform.

The lab also gives researchers access to the same type of production equipment used at battery factories, which ensures the scientists can get an accurate picture of how hot their batteries get during operation, how often they fail, how quickly they can be charged, etc. As some recent fires with the Samsung Galaxy Note 7 have shown, rigorous testing is critically important.

“Moving up from the first test cells to mass production of cell phone batteries is a giant leap,” Less said.

Less added that the Battery Lab is fairly new, and one of the leaders in the country for this type of work.

“Prior to the UM Battery Lab there were a few other places where someone could go to get this work done, but it was often difficult to gain access, expensive, risked compromising intellectual property or all of the above,” Less said.

Siegel said he thinks establishing a battery lab at the University shows how invested the University is.

“The University has invested in this technology in a way that no other university has,” Siegel said.

 

About the author

Jimmy is a 6th-year graduate student in the University of Michigan Department of Chemistry, exploring new chemical reactions to make photocatalysts for solar energy storage. He’s a southwestern Pennsylvania native and graduated from Duquesne Universtiy in Pittsburgh in 2011. Jimmy spends his off time at the roller hockey rink, playing involved board games, or annoying his cat. He also blogs chemistry and student issues at Tree Town Chemistry.

Read all posts by Jimmy here.

 

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Figure 1: Jimmy Brancho