A size comparison of a lithium-ion battery, left, a battery that uses a silicon composite anode, middle, and SolidEnergy’s “anodeless” prototype battery, right. All have the same energy capacity. (SolidEnergy Systems)

There may come a time when a single charge will be more than enough. Enough not just to get through a day, but several days worth of playing music, games, editing photos, surfing the web, socializing and countless other things we’ve grown accustomed to using our smartphones for. Perhaps it’ll even be enough to get us through the week. Dare to dream, I say!

That will, of course, require a scientific breakthrough of sorts — one that eventually leads to a vast improvement beyond the lithium-ion batteries we heavily rely on today. Such a breakthrough, by extension, would also be a watershed moment for ultraportable wearable devices such as smartwatches as well as drones, plug-in electric vehicles and numerous other technologies that haven’t yet lived up to the hype, in part due to the same limitations.

SolidEnergy Systems, a Boston-based start-up, is the latest in a crowded list of upstarts who claim to have come up with such a breakthrough. What’s notable here, though, is that they appear to be further along than most, having recently unveiled a prototype that their tests show lasts twice as long between charges compared to lithium-ion batteries of the same size. The results were certified by A123 Systems, a battery manufacturer who is collaborating on the project.

The prototype is for the most part similar, both in form and function, to what you’d find in current lithium-ion-based systems. There’s a pair of electrodes, an anode and cathode, along with an electrolyte that allows charged particles known as ions to flow between them as energy is released.

Much of the gains, then, were achieved by way of new materials, namely an anode made of lithium and copper rather than graphite. Measuring roughly one fifth the thickness and able to store 10 times as many ions, it’s this thin piece of metal foil that makes it possible to design cells that pack the same amount of energy density, but at roughly half the size. A standard 4-cell battery casing, for instance, can now accommodate twice as many.

While the concept of raising battery capacity through the use of what’s referred to as “anode-less technology” has been kicked around for decades, Qichao Hu, the company’s founder and chief executive, believes he has good reason for feeling a somewhat bold sense of optimism. For one, the prototype was assembled and tested at a nearby battery plant owned and operated by A123 Systems. Normally, experimental batteries are built inside research laboratories.

“From day one, we wanted to make sure that we weren’t developing something that couldn’t easily be replicated on a production line,” Hu says. “The battery we’re developing is something that can be put together using the same existing specialized equipment, techniques and criteria as what’s used for the ones being manufactured right now.”

The company also claims to have resolved a longstanding safety concern with this type of approach. It’s well known that combining a metal anode with an organic electrolyte fluid sets off a chemical reaction that greatly increases the risk of a hazardous fire. “You can go instead with a less flammable solid state electrolyte, but it won’t work at room temperatures,” Hu explains. “So we developed a proprietary liquid electrolyte mixture that’s both effective and much safer.”

Still, any significant improvement to a key aspect of how a battery functions typically necessitates some degree of sacrifice elsewhere. For instance, researchers searching for ways to boost energy density have in recent years turned to the possibility of high-capacity anodes made of silicon. The problem, though, is that charge and discharge cycles cause the material to swell and contract, leading to rapid degradation. To date, only Silicon Valley-based Amprius has come up with a commercial version, albeit with a more modest 20 percent boost in capacity.


This chart illustrates the scale of the overall energy density and size reduction of a power cell that uses Anode-less technology. (SolidEnergy Systems)

Metal anodes, meanwhile, are very thin and prone to break as well. The fix Hu and his research team have been perfecting involves applying a protective polymer coating that allows the anode to better withstand wear and tear. They’re also looking into fine-tuning the manufacturing process, along with enhancements to the electrolyte fluid, to get it to where it can survive at least 300 charge cycles, sufficient for smartphones. Their current prototype, assembled by hand, is said to last close to 100 charge cycles.

Even then, Hu acknowledges the countless hurdles in bringing the technology to market. Previous efforts have often run up against the fact that batteries, again, power a wide range of products and industries — each saddled with its own unique set of challenges. Herein lies the difficulty in demonstrating that what began as a materials science discovery can over the long term deliver the same performance advantages to buses the same way it can with tablet computers.

Dan Hearsch, a battery expert at the consulting firm AlixPartners, posits that many of the setbacks start-ups experience can be chalked up to instances in which the developers failed to properly take into account the nitty-gritty rigors of “real world” application.

“Solving the two major issues of overheating and limited cycles is one thing,” he says, “but carmakers will then need to know if a battery can work in all climates, whether it [can] also handle vibration or if it adds too much weight. That can be a deal-breaker, too.”

Just as important is the overarching question of whether the economics would ultimately make sense. In a bid to attract potential financiers, SolidEnergy has cited an internal estimate showing that producing its batteries at a scale of 12 million units would cost around $400 per kWh, about 80 percent of what it would cost for lithium-ion batteries. The plan going forward, Hu says, is for the company to negotiate arrangements to supply the electrolyte and anode components to large manufacturers.

John Wozniak, an independent tech consulting whose expertise in battery manufacturing included a five-year stint as a contractor for Energizer and 12 years as a “Distinguished Technologist,” at Hewlett Packard, says that while he finds the approach to be promising, he has his doubts. “Big manufacturers prefer to do it all in house, so they’d rather figure out how a new technology works and tweak the formula to get around a patent,” he says. “Licensing deals are possible but its something big, established manufacturers simply don’t do.”

“Unless,” he adds, “they have to.”

However, Wozniak did praise the ongoing developments out of Boston as having “the most potential” of the bunch — the bunch being several competing ideas that include the likes of lithium-air, lithium-sulfur and silicon. He said he’s considering reaching out to Microsoft to see if it wanted to encourage one of its battery suppliers to license the technology. “I suppose it might be a good idea to ping them to at least find out if they’ve put it through puncture tests and other safety protocols,” he adds.

At this point, SolidEnergy is in talks to custom-build a battery for Project Ara, a modular phone concept currently being developed by Google. They’ve also received some interest from makers of drones. Most UAVs can’t stay airborne for longer than 30 minutes before needing to be recharged.

Hu’s ambitious timeframe for expansion into several markets has the technology reaching a level where suitable for portable devices such as smartphones by the end of next year, and electric cars the year after. “I know there are some people who may be skeptical of whether we will finally see these significant leaps in battery life because making it happen requires materials improvements, which usually takes time,” he says.

But, he added, “it took us just one year to piece together a good working prototype, so who knows what we will accomplish next year.”