Sometimes batteries explode. The footage is frightening, but scientists and startups have long been working to build a safer battery. They’re tinkering with the design and testing new materials in hopes of solving the problem once and for all. But every approach seems to come with a catch, and the most practical solution, for now, might be the most boring one.
Improving batteries takes three main tacks: avoiding flammable liquids for a solid battery; making battery components fireproof; and, boringly, modifying slightly the existing features in a battery. It might be that change, at least for batteries, comes slowly.
To understand how researchers are trying to fix the problem, it’s important to know the basics of how batteries work, and why they break down. To be clear, we’re talking about lithium-ion batteries, which are the most common battery type because lithium holds so much energy. Scientists are also developing magnesium batteries (they’re slow) and sulfur batteries (they don’t last long), but li-ion is still king for now.
The lithium-ion battery is made of two electrodes, or electrical conductors, on opposite sides. Lithium ions move from one side to the other, helped by highly flammable chemicals in the middle called electrolytes.
There are a few different reasons batteries burst into flames. Most commonly, too much heat or bad battery design makes the electrolytes react in a way that creates heat, and then an uncontrolled positive feedback loop called “thermal runaway” that leads to fire. Battery manufacturers also put separators between the two sides of the battery to keep them from touching. If the separators malfunction, which is what happened in the Samsung case, energy is redirected to the electrolytes and that, too, leads to fire.
So how can we fix this?
One much-hyped solution is solid-state batteries. The idea is simple: instead of using flammable liquid electrolytes, make electrolytes out of solid materials; a solid battery is less likely to burst into flame. But it’s harder for ions to move through solids than through liquids, which means solid-state batteries are difficult to engineer, and expensive, and can have performance problems.
There are three major approaches to making solid-state batteries. You can make the electrolyte out of ceramics, glass, or polymers, explains Michael Zimmerman, a materials scientist at Tufts University and founder of solid-state battery company Ionic Materials.
Ceramics and glasses tend to be brittle, which makes them fracture easily once you apply pressure. (This downside will be intuitive for everyone who has ever broken dishware.) Ceramics and glass are also harder to manufacture in large quantities, says Zimmerman, which makes them impractical because we need a lot of batteries. Plus, the process of manufacturing them sometimes emits toxic gases.
Then there are polymers. Some polymers can conduct ions, but that usually only works at extremely high temperatures. Zimmerman’s team developed a polymer that can conduct ions at room temperature but is also flame-retardant. In one video, they demonstrate how it can be cut up into pieces without catching fire.
Now, Ionic Materials is working with battery manufacturers, who would need to change the way they build their battery to accommodate the new polymer. Hopefully, says Zimmerman, there will be cells available in the next two or three years.
Two or three years doesn’t sound too far away, but it’s also an old refrain. “It’s been promised that solid-state batteries are going to hit the market in the next two to three years for the past four to five years and investors are growing increasingly impatient with the progress of solid-state,” says Ian McClenny, an analyst at Navigant Research who specializes in battery research.
Almost all the electric-vehicle manufacturers that McClenny has spoken to say they’ve had breakthroughs in solid-state technology. (For example, automotive designer Henrik Fisker recently made this same claim.) But McClenny thinks almost all solid-state batteries are pretty far from commercialization. “I don’t think solid-state is really going to be an option until the early or mid-‘20s because the lifespan of the cells is not there yet,” he says. The “bread and butter” that drives battery innovation is electric vehicles and, right now, most solid-state batteries probably last for one and a half years. That might be acceptable for a phone, but it’s hardly feasible for an expensive electric car.
Another tactic in the quest for the safer battery is to make the electrolytes themselves fireproof, though still liquid. Surya Moganty is the chief technology officer of NOHMs Technologies. They’re developing electrolytes out of “ionic solids,” a material that is similar to salt, but liquid at room temperature.
Building this material into the electrolyte makes them flame-retardant, but, again, there can be issues with battery life. NOHMs is improving the formulations so that batteries with their technology can last up to 500 cycles, and also working with manufacturers to license the technology. A similar problem plagues the researchers who, last year, created a water-based battery. This battery is safe. Unlike other, less powerful water-based batteries, it can reach four volts, which is the same voltage as organic electrolytes. But it only worked for about 70 cycles and, as Moganty notes, battery companies want batteries that last for at least 500.
Of these exciting-sounding technologies, there doesn’t seem to be one that is poised to take over, says McClenny. These improvements are coming, and it’ll be great when they do. But despite breathless headlines, it won’t be in the very near future.
Right now, the most effective strategy probably doesn’t come from big changes and reinventing the battery. It comes from looking at existing features and improving them a bit. For example, batteries already contain a battery management system, which is software that monitors how the battery is doing and can detect if something is going wrong. One helpful fix would be to make the BMS better. After all, the management system is already part of every battery and manufacturers don’t need to find creative, costly ways to integrate a new technology. “Companies can use advanced sensors, or other ways of collecting cell-level data, especially in the case of large installations where you have thousands of cells that make up battery system,” McClenny says. “Being able to pinpoint the exact cell that’s not performing up to standard can increase the battery’s lifespan.”
This is similar to the approach taken by Amionx, a San Diego-based battery safety company. (That’s “Am-ionics.”) Amionx spun out of battery company American Lithium Energy, and its research originated with trying to create fireproof batteries for the military.
Their approach, called SafeCore, is a final line of defense, says chief operating officer Bill Davidson. SafeCore doesn’t change the components of the battery itself. It’s an extra layer of material inside the cell that stops the fire before it begins. When triggered by something like too much heat or too-high voltage, the layer breaks the connection between the electrodes and the part of the battery responsible for regulating how the electricity moves through the device. That shuts down the battery entirely.
Like the other companies, Amionx is focused on licensing the technology to existing battery manufacturers. But if that turns out to be too slow, they will think about building their own cells to take them to market. “I’d be disappointed if I didn’t see the product in the market in 2019,” says Davidson.
Despite high-profile cases of battery explosion — like that of Samsung’s Galaxy Note 7 phones — batteries today are, statistically speaking, safer than they were in the past. But the stakes are higher now than ever, too. Forget phones: the rise of electric vehicles has everyone interested — and their popularity, by the way, also means the rise of electric-vehicle battery fires. And there’s even talk about enormous batteries serving as backups for the traditional power grid and for renewable energy.
When it comes to safety, the easiest fix isn’t necessarily technological, but structural. Experts say we’ve already achieved almost 90 percent of the maximum battery life theoretically possible from the lithium-ion battery. We’re creating our own problems by pushing batteries to be faster and more powerful.
If companies made incremental improvements instead of looking for a fix quick—like making separators thinner to improve the energy and power densities—the batteries they built could be more sustainable, according to McClenny. Enhancing individual components leads to a more sustainable design that the company can continue to build upon.
If you minimize the mistakes in the first place, you have less need for technology to save you.