Cities will be linked with hundreds of small sensors to measure everything from pollution to traffic to weather in the not-too-distant future. 5G cell boxes will transmit ultra-fast wireless internet capable of downloading an entire movie to a phone in seconds. Wearable sensors that might be stitched into a shirt will monitor your movement, heart rate, and even perspiration chemicals.
Only one thing stands in the way of that future becoming a reality: the battery.
Shirley Meng, a professor of nanoengineering and materials science at the University of California, San Diego, told The Daily Beast, “The technology is close to being ready, it’s just the power source that isn’t there yet.” “You need something flexible and safe enough to wear right on your body in a wide variety of temperatures for something like wearable sensors.”
Lithium-ion is the most widely used battery technology in consumer electronics, with applications ranging from cellphones to electric cars. While lithium-ion batteries pack a lot of power into a compact box, they also use a liquid electrolyte that can catch fire if it gets too hot or is damaged. (Remember those Samsung phones that exploded?) This necessitates cautious storage and a stiff case, which isn’t ideal for a sweat-monitoring garment.
As a result, several businesses are considering a novel battery technology that can be bent and twisted, and that can be manufactured on a T-shirt screening machine rather than a gigafactory. These batteries, which are made of zinc, a more common metal than lithium, may be printed in as many forms and sizes as stickers.
Imprint Energy, based in Alameda, is one of the companies working on solid-state flexible zinc batteries. Co-founder and CEO Christine Ho started working in lithium-ion batteries as a student researcher at the University of California, Berkeley, but realized that the world would need an alternative, one that didn’t rely on mining that takes place outside the U.S. (According to a White House report, China controls 60 percent of the world’s lithium production.)
In January, Imprint rolled out a new battery design, ZinCore, that packs 10 times more power than previous models into a cell just one millimeter wide. Crucially, Ho told The Daily Beast, the batteries also have a wider temperature range. While most batteries slow significantly in the cold, the new version can withstand temperatures as low as -35 degrees Celsius (-31 degrees Fahrenheit), meaning it can be used to track and trace products that need to be chilled, like COVID vaccines.
Ho compared making the batteries to “packaging dirt,” because of how common the components are. “The majority of the components in our batteries are in vitamins,” she said.
And without a hard shell, those batteries can be shrunk, bent and twisted to fit into all sorts of tiny devices. Imprint is currently targeting two major markets. They can be used to power 5G cells and Internet of Things (IoT) sensors for smart cities. Imprint is also working with shipping companies on smart labels, which could send a location signal for valuable products or monitor the temperature on sensitive items like seafood or ice cream. Amid concerns about election security, Ho noted, smart labels on shipments of paper ballots powered by a wafer-thin battery could offer peace of mind.
“Batteries are often the largest real estate item on a smart label,” said Ho. “Ours can be almost invisible because it’s so small.” But Imprint’s ambitions aren’t just to stay miniature.
“Our ultimate mission is to become the de facto green, sustainable, safe alternative to lithium-ion,” Ho said. “This could be designed for large-scale applications. Someone could design this into cellphones, put batteries into walls, put them in really large structural things that have never had power before.”
Zinc batteries were once thought to be a passé technology. Because they couldn’t be easily recharged but the components were cheap, they were primarily used as disposal power sources. Most consumers encountered them in hearing aids, where they could easily be trashed. Now zinc batteries are “hot,” said Chunsheng Wang, director of the University of Maryland Center for Research in Extreme Batteries.
Zinc batteries, unlike lithium-ion batteries, which rely on rare materials and pose substantial safety issues, are “intrinsically safe and available,” according to Wang. However, recharging has been a huge problem. When typical zinc batteries are reversed to draw in and store power, zinc can concentrate in certain areas on the anode where voltage is most strong, generating dendrites that eventually short out the cells. While the restrictions vary depending on the chemical and design, most batteries are only capable of a few hundred cycles.
Researchers—including Wang—have worked on modifying the electrolyte to reduce that damage and allow for faster recharging. One study from Hanyang University in the Republic of Korea reported a high-performance zinc-air cell that stayed stable over 30,000 cycles.
The applications, boosters say, could be widespread because of the flexibility of the technology. There is a promise for energy storage for renewable energy production as an alternative to large lithium-ion projects. Companies like Zinc8 are adapting zinc-air batteries for large-scale energy storage that could power the electric grid; the company recently announced a pilot project at a Queen’s apartment complex, following a pilot at the University of Buffalo in 2021.
However, the chemistry advantages also make them work on a small scale. Meng’s UCSD lab worked with hearing aid battery company ZPower (now renamed Riot Energy) on silver-zinc oxide batteries whose parts could all be essentially condensed into ink form. They could then be screen-printed onto thin films with an electrode sandwiched between to make a battery less than 1 millimeter thick. According to a 2020 paper published in Joule, that battery produced at least five times the power of the same size lithium-ion battery, although recharging was still limited.
Furthermore, the chemical benefits that make zinc safer also make it easier to mass manufacture. “Water in the manufacturing process does not accept lithium ion, therefore this extremely robust casing is required,” Meng stated. “Manufacturing in the open air is considerably easier for us.” There’s no need to construct a dry room.”
This offers up a lot of possibilities because batteries can be mass-produced with ink barrels in many forms and sizes.
“The first big stumbling block is a shift in thinking,” Meng explained. “Despite all of the research into lithium-based batteries, there has been relatively little advancement on zinc. People believe that zinc chemistry is complete. That’s just incorrect.”
According to Imprint’s Ho, the business will announce a manufacturing partner shortly, expanding on the company’s previous screen printing expertise while keeping flexibility in mind. “There won’t be an AA battery for IoT devices,” she predicted, implying that the capacity to change the size, shape, and power index on a daily—or even hourly—basis might open up new industries.
“We get approached all the time about all the different uses, from contact lenses to large-scale deployments.” And so many of them have the ability to change the world or people’s lives,” Ho remarked. “It’s amazing to think of how far lithium ion has gone in cars and consumer gadgets since it was first introduced 45 years ago.” This synergy, I believe, will take us on a similar trip.”Home Automation >> News & Updates >> The Flexible Batteries That Could Power Small Tech’s Future