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Energy Storage

Entrepreneur rethinks lithium-ion batteries with an eye toward storing renewable energy

Chemist Amy Prieto of Colorado State University discusses her work to commercialize a safer, more customizable battery

by Prachi Patel, special to C&EN
July 16, 2018 | APPEARED IN VOLUME 96, ISSUE 29

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Credit: Katie Hoffner/Prieto Battery

Amy Prieto decided to pursue battery research when she started as an assistant professor of chemistry at Colorado State University in 2005. The field was a perfect bridge between her Ph.D. studies in solid-state materials for electronic devices and her postdoctoral work in measuring transport properties of nanostructured materials. It turned out to be a fruitful decision. She has patented novel battery materials and a unique manufacturing process that together revamp decades-old lithium-ion technology. Her lithium-ion battery, built on a foundation of electroplated copper foam, is more flexible, safer, less expensive, and more environmentally friendly than batteries currently on the market.

Vitals

Birthplace: Bogotá, Colombia

Hometown: Fort Collins, Colo.

Studies: B.A., chemistry and philosophy, Williams College, 1996; Ph.D., inorganic chemistry, University of California, Berkeley, 2001

Professional highlights: Postdoctoral research fellow, Harvard University, 2002–05; professor, Colorado State University, 2005–present; founder, CEO, and chief scientific officer, Prieto Battery, 2009–present

Why battery research is fun: I love the kinds of problems where theorists have predicted some property or somebody has sketched a battery architecture, but no one knows how to make the materials go together. It’s a lot like cooking, which I love.

On getting the Presidential Early Career Award for Scientists & Engineers (2012) at the White House: It was incredible on many levels. I was fortunate to receive the award from President Obama, who gave a moving speech about the incredible need for diversity in science, which I feel strongly about.

In 2009, just four years after embarking on her research, she founded a company, Prieto Battery, to develop the technology for commercial use. The start-up caught the eyes of the power-tool manufacturer Stanley Black & Decker and the computer technology giant Intel, both of which invested in the technology in 2016. Prachi Patel talked with Prieto about her innovative technology and business plans.

Why give lithium-ion batteries a makeover?

Current batteries are limited by their materials and architectures. In your cell phone or laptop, you have a battery made of flat layers. If you want it to store a lot of energy, you have to make the layers thick, which means the battery doesn’t charge very quickly. And if you want to make it fast, you have to make those layers thin, but then you cannot store very much energy.

We wanted to make a device without these trade-offs so your phone battery could last a whole day and you’d be able to charge it in 10 minutes instead of an hour. That’s critical for larger-scale energy storage applications like electric vehicles or my ultimate dream: battery banks for wind and solar farms.

How did you start thinking about this problem?

Originally, I was not thinking about something that could be commercialized quickly but was looking for enriching research for my students and postdocs. From the beginning, we wanted a manufacturing method that was scalable and environmentally friendly and did not require expensive capital equipment, high temperatures, or long processing times. So we decided on electroplating, a really good method to deposit ions from a solution onto an immersed surface using electric current. It’s never been used for batteries, but it is used for coating jewelry, car parts, and interconnects on semiconductor chips.

Today’s batteries use flat metal sheets that are coated with anode and cathode materials. We start with a three-dimensional copper foam, which has a high surface area because it is porous, so you can get more capacity in the same footprint as a standard battery. But you can still have fast charge and discharge because ions move through the porous foam easily.

The foam goes into our electroplating bath containing an aqueous solution of citric acid with dissolved copper and antimony salts. Those salts deposit on the foam surface as copper antimonide, a known anode material. All these materials are nontoxic. Antimony by itself is not the most environmentally friendly, but it’s very stable in copper antimonide. Next, we electrochemically coat the foam with a proprietary polymer that we formulated, which acts as the electrolyte and the electrode separator. Finally, we coat the foam with a slurry of cathode materials, including lithium cobalt oxide and lithium nickel manganese cobalt oxide, which we buy from suppliers.

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Many others are pursuing novel lithium battery chemistries. What gives your design an edge?

A key aspect is that electroplating allows us to customize our battery volume and make it in a variety of sizes and shapes. We can control the thickness of the anode coating based on the amount of charge we pass during electroplating. There are many applications, such as wearable devices, where device designers are limited because they cannot find batteries that conform to the volume requirements. We can let designers daydream and make a battery that fits their space constraint.

Another big advantage of our battery is safety. Most batteries today have graphite anodes. If you overcharge them, you can get lithium plating on the graphite surface. These metal deposits form spiky growths called dendrites that cause a short circuit, which can lead to battery fires. Copper antimonide takes up lithium ions during charging in a way that doesn’t allow lithium plating. It is also thermally conductive, so it dissipates heat and helps the battery handle overheating. Plus, this is a solid-state battery, so we don’t have flammable liquid electrolytes.

We provide the next step for lithium-ion batteries by mostly using chemistry that’s understood today.

Some people in the battery industry are working on new chemistries that are critical for technologies that we will need in 10–20 years. And others are optimizing the engineering of current batteries to get a couple percent improvement every year. We fall between those two. We provide the next step for lithium-ion batteries by mostly using chemistry that’s understood today. Our technology is something that can be commercialized in the near future.

Tell me about your start-up and your business partnerships. What are your targets and timelines?

My business partner and I have a goal to have our very first batteries on the market within this calendar year. Most start-ups raise a lot of money and build a whole facility. We decided to instead raise only what we needed as we went and then to try to focus on establishing partnerships. We targeted companies that really needed new batteries. Intel is interested in flexible battery sizes and formats for computing devices. Stanley Black & Decker makes things you’d imagine on a construction site, and the company is interested in power and safety. So the markets are different but complementary in that they both place a high value on tech and innovation.

Our manufacturing partner is Moses Lake Industries, which develops electroplating chemicals and processes for companies like Intel and Samsung. They are scaling up the process, so we don’t have to build a new facility. Electroplating is used in a variety of industries, so we don’t foresee any real technical challenges.

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Prachi Patel is a freelance writer. A version of this story appeared in ACS Central Science: cenm.ag/prieto. This interview was edited for length and clarity..

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