This New Solid-State Battery Design Will Offer 10-minute Charge And 6,000 Cycles

A team of scientists from Harvard have devised a solid-state battery that can resist dendrites, a problem that has dogged solid-state batteries since the automakers began trying to put them into cars. While solid-state batteries (or SSBs) promise to handle fast-charging better than any current-generation EV battery, they are not immune to degradation. Dendrites are one of the leading reasons solid-state batteries reach the end of their useful lives.

While a lot of the hype around solid-state batteries focuses on the increased driving range between charges, the dramatically shorter driving times may ultimately prove to be the bigger selling point. Lithium-ion batteries do not respond well to massive incoming surges of electricity. Fast-charging wears them out and makes them need replacement sooner.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from various manufacturer websites and other authoritative sources, including Edmunds, TopGear, and Interesting Engineering.

Making Lithium Behave Instead Of Forming Dendrite Spikes

• The battery design uses a special material for the electrode that contains tiny silicon particles.
• When lithium separates out of the battery, it forms a thin plating on the electrode instead of spiky crystals.
• The test batteries retained 80-percent of their capacity after being drained and recharged 6,000 times.
• This laboratory has published extensive research into solid-state batteries and the materials that go into them.
• While the prototype batteries were larger than most solid-state batteries available today, they are tiny compared to what would be needed to power an EV.

The battery design intersperses the battery’s anode with micrometer-sized silicon particles. This means that when lithium separates out of the battery from extended use, it doesn’t form spikes that recklessly puncture the battery from within. Instead, they form a sort of plating around the electrode. As lead scientist Dr. Xin Li stated, “In our design, lithium metal gets wrapped around the silicon particle, like a hard chocolate shell around a hazelnut core in a chocolate truffle.”

Previous Dendrite Research From Harvard

This isn’t Li’s first work in the ongoing scientific war against dendrites. Solid-state batteries are a specialty of Li’s lab, being the focus of 12 science journal publications since 2021. (Of course, Dr. Li and his team also work in other fields, all of which are related to the storage and conduction of energy.) An earlier research project produced a multilayered battery design that effectively confined dendrites to a single zone in a “multilayered design.” In effect, Li and the scientists in his research team devised a way to contain the dendrites within the battery.

The Results From Testing The Silicon-Infused Electrode Suggest Success

The results of the silicon-electrode battery have been promising. After being drained and recharged 6,000 times, the test batteries retained 80-percent of their original capacity. If Harvard’s test results transfer to EV-sized batteries, it would mean the vehicle could be fast-charged once a day and still retain 80-percent of its capacity after 16 years.

Very few people want to think about battery loss in an aging EV, just as ICE drivers don’t like to consider the decline of horsepower as the odometer reading rises. But as anyone with an aging phone knows, any battery loses capacity with age and use. While the battery out of Dr. Li’s lab was no longer “like new” after 6,000 simulated use cycles, it still had ample capacity.

But even if this design passes all laboratory tests and makes it into production, it isn’t ready for cars yet. While the team’s prototype battery was “ten to twenty” times the size of currently-made solid-state batteries, it is still impossibly tiny compared to the size of a battery that could power a car. EV-sized SSBs may be coming closer, but they still are not here.

Dendrites: An Overview

• Dendrites are lithium crystals that form on battery electrodes.
• They cause aging solid-state batteries to destroy themselves from the inside out.
• While dendrites are one reason SSBs aren’t yet in every EV, other factors keep them confined to the laboratory for the time being.

Dendrites are small lithium crystals that form on the anode of batteries (the anode is one of the two electrodes to which the car’s wiring is connected). When examined under a microscope, they look like small, spiky, metal trees. They form as the lithium ions inside a battery get pushed back and forth whenever the battery gets drained and then charged up again.

As this happens, some of the lithium separates out of the electrode and takes root in microscopic cracks (called “microfissures”) that form in the anode. Like weeds wedging their roots through pavement cracks, the dendrites grow out of these cracks.

Dendrites Are A Leading Cause Of SSB Death

Dendrites are one of the primary reasons solid-state batteries reach the end of their life. Because they’re made of lithium (which is, of course, a metal), they can conduct electricity. As the dendrites grow inside the battery, they puncture the battery’s internal layers and carry electricity to places it wasn’t meant to go. In other words, the battery short-circuits itself to death from the inside.

If an SSB installed in a car developed dendrites, the driver would first notice that the battery “doesn’t seem to last as long as it used to” between charges. But after a while, the battery could eventually overheat and possibly even catch fire. While eliminating dendrites wouldn’t yield everlasting solid-state batteries, they would last a lot longer.

There Are Other Reasons Solid-State Batteries Aren’t Yet In Every EV

Dendrites aren’t the only reason SSBs haven’t hit the road yet. At present, solid-state batteries remain relatively expensive to produce, which could raise the MSRP too high for most customers. Additionally, the looming threat of a worldwide lithium shortage hangs over SSB development like the sword of Damocles that could fall at any second.

Research Into Preventing Dendrites Is Growing

• Research into solid-state batteries, including preventing dendrites, is growing.
• Honda has developed a battery with internal barrier layers to prevent lithium from touching the electrode, much less forming crystals in it.
• Graphene batteries don’t use any lithium at all, and therefore can’t form dendrites.

Of course, Harvard researchers aren’t the only ones trying to forestall battery dendrites. With so much of the auto industry trying to pivot to solid-state, a lot of money is going into SSBs. While information is scarce (possibly due to as-yet incomplete science or companies trying to guard their trade secrets), some information has gotten out.

Honda Has Developed An SSB With A Dendrite-Preventing Protective Layer

Perhaps the most notable solution to dendrites comes from Honda. The Japanese automaker’s answer to the persistent dendrite problem is to put a protective barrier layer between the battery’s electrodes and the electrolyte. In theory, if the lithium in the battery can’t touch the dendrite, it can’t reach into any cracks that form on it. So the thinking goes, this will completely prevent dendrites (or at least delay their formation by a long time).

Honda’s solution of essentially putting a protective wrapper over the electrodes is so simple that it’s almost surprising that it might work. When it comes to scientific development, the seemingly simple solutions often fail under the weight of real-world complications. However, while Honda hasn’t yet put one of its polymer-protected batteries into a working vehicle, the technology has been promising enough to justify a few press releases.

Graphene Batteries Can’t Form Dendrites

While most SSB research has focused on eliminating dendrites by making it impossible (or at least very difficult) for the lithium to crystallize out of the battery’s electrolyte, other battery designs attempt eliminate the problem altogether. Some batteries use a material called graphene in the electrodes. Graphene is the name of single-atom-thickness sheets of graphite (yes, the stuff in pencils).

In essence, graphene is carbon in its most two-dimensional form. Of course, transmitting electricity through carbon is an old technology. The so-called “brushes” in universal motors have done this for over a century. However, graphene is a relatively new area of scientific territory. But despite the current research buzz, large-scale production of car-sized graphene batteries (if it ever happens) is in the far future. So far, Stellantis is the only major company in the auto industry to fling moneybags into graphene hopes.

The Auto Industry’s Long Drive To Make Solid-State Batteries Succeed

Solid-state batteries continue to tantalize the automotive industry. They weigh far less than lithium-ion batteries with the same energy capacity (battery weight has been a notorious problem for EVs). They can also charge a lot faster without wearing out so severely.

While the average gasoline or diesel car can be refueled in about the time it takes to send a few text messages, electric cars tend to require at least an hour or two on a charging socket. However, the forthcoming generation of solid-state batteries could charge in 10 minutes or less. While that’s not as fast as refilling a tank of gasoline, it would reduce charging to a short, forgettable inconvenience.

In theory, SSBs have far longer lifespans. Some solid-state batteries could even be good for the life of the car, which would eliminate the growing worry about the ruinously high cost of EV battery swaps. Volkswagen has an SSB in the works that may last for 310,000 miles (though nothing is certain in the testing phase), which is longer than most cars survive.

Dendrites Are Only One Problem Getting In The Way Of Solid-State Batteries

Of course, dendrites aren’t the only problem keeping solid-state batteries off of the road. While solid-state batteries have existed for decades, they have really only worked for very small devices like hearing aids (and more recently, wearable technology). The possibility remains that they will never quite take off. It wouldn’t be the first time that years of technological research ended with nothing but embarrassing entries in many companies’ financial ledgers.

The Uncertain (Yet Tantalizing) Future Of SSBs

While lithium-ion batteries have certainly proven adequate for the EVs of today, complacency never turned a profit for long. The competition to be the first company to get a solid-state battery into a production vehicle is fierce. The closest any company has come to solid-state success is Chinese EV manufacturer Nio, who put a semi-solid state battery into a car and drove it for 648 miles without recharging. However, the title of “first company with a solid-state EV” remains open. Whoever achieves this feat may owe a credit and a patent licensing fee to these Harvard scientists.