"Did you see what happened over the weekend?” asked Michael Zimmerman as he called up a news story on his laptop. It was June, and the Tufts engineering professor of the practice was in a conference room looking at a video of a Tesla Model S sedan, flames shooting from its undercarriage like something from a rocket. The fire wasn’t the result of a crash—the shocked driver later said he was just sitting in California traffic when his car began to smoke, then burst into flames. The electric car’s massive battery pack was eventually identified as the culprit. There haven’t been many reports of Tesla batteries failing in such spectacular fashion—the company called the fire “an extraordinarily unusual occurrence”—but this wasn’t the first time it had happened. “I have a Tesla,” Zimmerman said. “It scares the crap out of me.”

What makes Zimmerman nervous, specifically, is the liquid electrolyte in the car’s lithium-ion batteries. And it’s easy to see why when you start adding up the tales of disaster related to this battery material, which is used in everything from smartwatches to airplanes. In 2013, battery fires on Boeing’s 787 Dreamliner airliner forced the grounding of an entire fleet of planes for the first time in more than three decades. And during the hoverboard craze of 2015, dozens of reported battery fires led the US Postal Service to issue a ban on sending the gadgets through the mail. The next year, owners of the Galaxy Note 7 smartphone began reporting that their devices were catching fire (and occasionally exploding). Samsung ended up recalling roughly 2.5 million of the devices worldwide, causing the company’s market value to temporarily drop by $26 billion.

Michael Zimmerman

Michael Zimmerman, Tufts engineering professor of the practice, has developed a rechargeable battery that won’t catch fire, explode, or stop working even when shot with a rifle.

A propensity to burst into flames is only part of the problem. Despite the spectacular technological advances in our phones, laptops, and electric vehicles, the lithium-ion batteries that power them haven’t really changed since they were first introduced in the 1990s. Our smartphones offer more than a hundred times more processing speed than they did when the iPhone was introduced a decade ago, yet the energy density of phone batteries has barely increased at all. Our batteries never run as long as we want them to, and they only get worse as they age. And these limitations have ramifications that go far beyond inconvenience. The shortcomings of our current battery technology are also compromising our ability to implement massive changes in the way we produce and consume energy—and that’s part of what’s preventing us from breaking our dependence on fossil fuels. Until we have better ways to store the energy produced from renewable sources like wind and solar, we remain destined for a carbon-based future.

With stakes that high, the search to develop a better battery is a quest for the holy grail. Along the way, researchers have begun to rethink the materials used for the electrolyte. Developing a replacement for the unstable liquid electrolyte used in current batteries could unlock the door to a safer, less expensive, much more powerful battery. Engineers around the world are experimenting with alternatives, such as electrolytes made of everything from ceramic to glass. But these innovations have yet to produce the kind
of breakthrough that everyone is hoping for.

“In batteries, since the whole thing is kind of stuck, you have a thousand different exotic experiments,” said Bill Joy, cofounder of Sun Microsystems and a venture capitalist who has backed several green energy companies. “People are trying everything they can think of. They may be interesting at the scientific level, but they are not manufacturable enough to imagine using them in production.” For his part, Tesla CEO Elon Musk used a conference call with analysts last year to express his impatience with every “battery breakthrough du jour.” He went on to dismissively point out that “everything works on PowerPoint. If you like, I’ll give you a PowerPoint presentation about teleportation to the Andromeda Galaxy.”

Now, however, things could finally be changing, and Tufts engineers are helping to lead the way. Zimmerman, who has taught at the School of Engineering for more than twenty years, has developed a battery using an electrolyte made of plastic instead of liquid that is so promising, his company, Ionic Materials, recently attracted a $65 million round of investment from the likes of Bill Joy, Samsung, Hyundai, Renault, Nissan, and Mitsubishi. Meanwhile, recent Tufts doctoral graduate Anthony D’Angelo—working with Matthew Panzer, associate professor of chemical and biological engineering—developed a battery with an electrolyte made of gel, an innovation that won him the top prize in a $100,000 startup competition.

For all the recent progress, the race to build a better, safer, and more efficient battery has only just begun. The competition is fierce, but the potential rewards are enormous. There’s also the fact that it might just save the planet.

The rechargeable lithium-ion battery was introduced ages ago, if you’re measuring in engineering time. Sony first offered it to consumers in the early nineties as a new feature for one of the company’s camcorders. It was a massive hit. But even as the lithium-ion battery has become ubiquitous—today it’s a $55 billion annual market in the US alone, growing 10 percent every year—the basic design hasn’t really changed.

Here’s how it works. A battery contains a positive electrode and a negative electrode. In between is a liquid electrolyte that conducts positively charged lithium particles, called ions. When the battery is in use, the ions move through the electrolyte, from the negative side to the positive, releasing energy that powers your laptop or phone. Connect the device to a charger, and the ions shuttle back to the negative side, where they’re stored until they’re needed to provide power again.

The trouble with lithium-ion batteries lies in the materials used to make those components. Consider the carbon and lithium cobalt oxide that are commonly used in the two electrodes, and the lithium salt in solvents for the liquid electrolyte. “You couldn’t find three worse materials to put together,” Zimmerman said. For starters, the ingredients are expensive and difficult to source. Then, only a thin, plastic separator keeps the electrodes from touching. When a puncture or other problem with the separator causes a short circuit, the battery quickly heats up, and the liquid electrolyte begins to leak and vaporize. And if the escaping material is exposed to oxygen, it catches fire. “The liquid electrolyte is like kerosene,” Zimmerman said. “It can blow up.” Given all this, Zimmerman reasoned that there had to be a better design, and he had some ideas about how to find it.

Matthew Panzer

Associate Professor Matthew Panzer, who heads Tufts’ Green Energy and Nanostructured Electronics Laboratory, has helped design a safe and efficient battery that uses a gel electrolyte.

Unlike Benjamin Braddock in The Graduate, the young Michael Zimmerman never needed anyone to tell him that there was going to be a great future in plastics. He studied polymers—the building blocks of plastics—at Rensselaer Polytechnic Institute, MIT, and the University of Pennsylvania, where he earned his PhD. In 2002, he founded Quantum Leap Packaging, which made a polymer to protect semiconductors. After selling the company in 2009, he turned his attention to the battery problem. How, Zimmerman wondered, could you design a battery without the problematic liquid electrolyte? He reasoned that polymers could hold the answer. They could be designed with good chemical resistance and good stability against voltage.

Experimenting in the basement of his home in Massachusetts, where he has equipment for heating, mixing, and extruding plastics, Zimmerman started manipulating polymers at the molecular level. He eventually came up with an entirely new composition of matter—a plastic that could conduct ions. Rather than the ions flowing smoothly through a liquid electrolyte, the way they do in a traditional lithium-ion battery, they hopped through the molecular structure of the polymer, skipping their way from cathode to anode. To test his new electrolyte invention, he put it in a small battery that he placed in a watch. The second hand ticked to life, and he knew that he had found what he was looking for.

Because his electrolyte was made of a solid piece of polymer, there was no need for a separator to prevent a short circuit. But Zimmerman still had to find out if it was safe.So he cut his battery prototype with scissors and pounded nails through it—not even a spark. He and his team shot the prototype with a rifle. No flames. No explosion. When the target practice was over, Zimmerman attached the mutilated, Swiss cheese of a battery to a smartphone, and it powered on. He came back twenty-four hours later, and the phone was still running.  

Powered Up illustration

Illustration by Amber Day

As promising as it was, Zimmerman’s progress was only the beginning. For instance, it turned out that his polymer electrolyte can work safely with lithium metal, a material that offers incredible battery performance but has been considered far too dangerous to use with liquid electrolyte. A lithium-metal battery could last ten times longer than a lithium-ion one—imagine a cellphone that goes ten days without a charge, or an electric car that can travel a thousand miles between plug-ins. Zimmerman won a $3 million Department of Energy grant, in 2016, to devise just such a battery.

Even more exciting is Zimmerman’s work on another version of his polymer electrolyte. Instead of using the pricey lithium, it could work with the inexpensive ingredients found in old-fashioned alkaline batteries—such as those delightfully safe Duracells and Everreadys—to create inexpensive rechargeables just as powerful as lithium-ion batteries. “What’s beautiful about the alkaline anode and cathode is they are extremely cheap, abundant materials,” Zimmerman said.

Bill Joy, the Sun Microsystems cofounder, became an early investor in Zimmerman’s company, in part because he believes it can deliver on the promise of a rechargeable alkaline system. The company could even someday develop a way for alkalines to power cars, Joy said. “The raw materials for a car battery would cost $300 instead of $3,000,” he said. That could make a huge difference in the cost of electric vehicles, and in the number of people willing to buy them.

At Tesla, Elon Musk is taking a different tack, doubling down on traditional lithium-ion batteries and looking to drive down battery costs through economies of scale. He built a “Gigafactory” outside Reno, Nevada, that he says will nearly double the current world production of lithium-ion batteries, soon getting the cost of batteries down to $100 per kilowatt hour of energy, the price the Department of Energy estimates would finally make electric cars competitive with gas-powered ones.

Today’s technologies promise a better tomorrow—more powerful devices, affordable electric cars, a cleaner energy supply—but we’re being held back by battery design that hasn’t improved in decades. Now Michael Zimmerman, a Tufts University professor of the practice in mechanical engineering, and his company Ionic Materials have invented a new kind of battery to be safer, less expensive and more powerful.

Whether costs come down from economies of scale or new technology, an affordable electric car would be groundbreaking. But Bill Joy sees even bigger things in Zimmerman’s pursuit of cheap, rechargeable alkaline batteries: He thinks they could lead to efficient, economical batteries capable of storing energy from renewable sources like wind and solar. With a game-changer like that, Joy said, a future of 100 percent renewable energy suddenly looks like a real possibility. That would break our addiction to oil, he said, drastically reducing our greenhouse gas emissions and slowing climate change: “If you have a combination of wind, solar, and cheap batteries, then you should be able to fully decarbonize the grid.”

Today, more than 62 percent of the electricity used in the US still comes from power plants that burn natural gas, coal, and other fossil fuels. These sources exact a significant toll on the environment, but we stick with them in part because they reliably produce energy whenever we need it. Renewable energy sources like wind and solar power, on the other hand, are earth-friendly, but don’t produce electricity when the wind isn’t blowing or the sun isn’t shining. And that helps explain why only about 6 percent of America’s electricity comes from wind and just 1 percent is from solar.

The solution to the problem may lie in batteries that can store the power created when the wind is blowing and the sun is shining. In just one example of this technology, Tesla has taken the battery system it uses in its cars and essentially supersized it to create a 20-megawatt “Powerpack” that can store enough energy for about 2,500 homes. Some power companies have invested in these batteries, but many others have not because they can be expensive to run and potentially degrade quickly. The batteries just aren’t good enough right now.

Zimmerman’s work with alkalines could be one way to change that. Another could come from another Tufts engineering alum, Neil Puester, E66, who has worked on batteries his entire career. His most recent company, Nilar, has changed the structure of the tried-and-true rechargeable nickel metal hydride battery so that it does not get as hot as other batteries, thereby extending its life. It’s a smart, but practical, design change. Among other adopters, it’s already being used by a shopping mall that stores energy from its solar panels to power its stores and charge customers’ electric vehicles.

A third possible solution to the grid-storage problem is being developed by Anthony D’Angelo, the doctoral graduate from Tufts’ Department of Chemical and Biological Engineering. Like Zimmerman, D’Angelo is focused on developing a new kind of electrolyte. Rather than using polymers, however, D’Angelo is working with a kind of gel.

Anthony D’Angelo

With a plan for batteries to safely and affordably store energy created from renewable sources like solar, Tufts engineering PhD Anthony D’Angelo’s company won top prize at a recent MIT competition.

The idea behind D’Angelo’s approach began in Tufts’ Green Energy and Nanostructured Electronics Laboratory. The lab is headed by Matthew Panzer, the Tufts associate professor, who has spent many years researching gel electrolytes. Manufacturing an electrolyte made of gel, unlike some other materials, is fairly easy, Panzer said. It starts with a new kind of salt compound that stays liquid at room temperature. Then Panzer adds a polymer that holds the liquid salt in a gel state. When it’s done, the electrolyte—which gets mixed up in thirty minutes—looks like a slice from a clear gummy bear.

Because the gel can conduct ions, Panzer was originally looking at it as a material for use in electrical switches in transistors. But when D’Angelo joined his lab as a PhD student in 2013, he and Panzer started to think about how the gel could solve the safety problem in lithium-ion batteries. “The ionic liquids we use are non-volatile, don’t evaporate, don’t easily catch on fire,” Panzer said. And because the gel is solid enough to keep the electrodes from touching, batteries using it don’t need a plastic separator to guard against an explosive short circuit. The gel’s flexibility and safety make it ideal for wearables such as smartwatches, but D’Angelo’s vision is to use it for much larger batteries, ones with the ability to store the power created from wind and solar.

In April, D’Angelo got the chance to make his case at MIT’s Clean Energy Prize competition, a high-profile annual event in which students from around the world pitch their ideas for green technologies. With his Tufts PhD dissertation due the next day, D’Angelo made his presentation to the judges. “When you open a battery now, it’s essentially using the same materials it used twenty years ago,” he told them. “There’s really a need for a more robust and energy-efficient battery.” D’Angelo explained that the company he cofounded, Lithio Storage, could use commercially available chemicals to produce massive grid-scale batteries that are far safer and more economical than anything else on the market.

As his presentation continued, D’Angelo said that one of the problems with the batteries currently used for grid storage is that they get very hot very fast. And if they reach about 120 degrees Fahrenheit, he told the judges, the liquid electrolyte begins to degrade, soon “making the battery essentially unusable.” Getting around that, he explained, has involved devoting 8 percent of total grid-storage spending on industrial air conditioning systems that keep the batteries below that temperature red line. D’Angelo’s batteries would eliminate the need for the air conditioning, he said, because his gel electrolyte remains stable at temperatures up to 176 degrees. Used in just one of Tesla’s Powerpack systems, D’Angelo’s battery could save power companies about $5 million per year. Those kinds of savings could really start to add up as more power companies adopt battery systems—one recent report estimated that the energy storage market, which was $302 million in 2017, will grow to $4.3 billion by 2023.

In the end, the MIT judges praised D’Angelo’s presentation for its “clear clean energy impact,” “great market opportunity,” and “great explanation of how this solution fits into the existing landscape.” They awarded his company the $100,000 first prize.

At the end of May, Michael Zimmerman’s company, Ionic Materials, cut the ribbon on its new home, a 35,000-square-foot facility with lab and office space in the Boston suburb of Woburn. By the next month, the company had grown to thirty-five employees, including some Tufts engineering graduates. The most recent hire? Anthony D’Angelo, the freshly minted Tufts PhD.

With Ionic Materials D’Angelo saw a chance to join a battery research company that was making progress quickly. “They are doing fantastic things,” D’Angelo said. “I’m very interested in learning: How did they develop their company? How did they get their investors? There’s still a lot for me to learn.” He is looking forward to having an entrepreneur like Zimmerman as a mentor.

For his part, Zimmerman has been thinking a lot lately about his own first mentor, George Low, who was president of Rensselaer Polytechnic Institute when Zimmerman was an undergrad. Low, a driving force behind NASA’s moon program, told him that successful engineering is about seeing opportunities and taking them. If Zimmerman had the opportunity, he should work on something meaningful. “I think I’ve seized the opportunity,” Zimmerman said. “I think he would be proud that I’m working on something meaningful.”

Julie Flaherty

Julie Flaherty, senior writer and editor at Tufts and editor of Tufts Nutrition, can be reached at julie.flaherty@tufts.edu.