"World's fastest electrodes" triple the density of lithium batteries
French company Nawa technologies says it's already in production on a new electrode design that can radically boost the performance of existing and future battery chemistries, delivering up to 3x the energy density, 10x the power, vastly faster charging and battery lifespans up to five times as long.
Nawa is already known for its work in the ultracapacitor market, and the company has announced that the same high-tech electrodes it uses on those ultracapacitors can be adapted for current-gen lithium-ion batteries, among others, to realize some tremendous, game-changing benefits.
It all comes down to how the active material is held in the electrode, and the route the ions in that material have to take to deliver their charge. Today's typical activated carbon electrode is made with a mix of powders, additives and binders. Where carbon nanotubes are used, they're typically stuck on in a jumbled, "tangled spaghetti" fashion. This gives the charge-carrying ions a random, chaotic and frequently blocked path to traverse on their way to the current collector under load.
Nawa's vertically aligned carbon nanotubes, on the other hand, create an anode or cathode structure more like a hairbrush, with a hundred billion straight, highly conductive nanotubes poking up out of every square centimeter. Each of these tiny, securely rooted poles is then coated with active material, be it lithium-ion or something else.
The result is a drastic reduction in the mean free path of the ions – the distance the charge needs to travel to get in or out of the battery – since every blob of lithium is more or less directly attached to a nanotube, which acts as a straight-line highway and part of the current collector. "The distance the ion needs to move is just a few nanometers through the lithium material," Nawa Founder and CTO Pascal Boulanger tells us, "instead of micrometers with a plain electrode."
This radically boosts the power density – the battery's ability to deliver fast charge and discharge rates – by a factor of up to 10x, meaning that smaller batteries can put out 10 times more power, and the charging times for these batteries can be brought down just as drastically. Nawa says a five-minute charge should be able to take you from 0-80 percent given the right charging infrastructure.
Also, because there are gaps in that ultra-lightweight nanotube scaffolding and less extraneous binder and additive materials, a battery containing a given amount of active material can become much, much lighter and more compact. Energy density, both by weight and by volume, stands to jump by factors of 2-3.
Oh, and the rigid structure and vast surface area of that nanotube array, as well as the broad distribution of tiny lithium blobs attached to it, eliminate a number of factors that cause batteries to dwindle, lose performance and die over time. Nawa says a battery's lifespan should be five times longer using this technology.
"Making a battery is very difficult," says Boulanger. "You have to master a lot of parameters. But if you want to master those parameters, you need to have the highest electrical conductivity. You need to have the highest thermal conductivity. You need to have the highest ionic conductivity. And that's exactly what our material can bring to battery makers."
At around this point, we'd expect to find a catch, so we reached out to seek a reality check from Dr. Cameron Shearer, Research Fellow at the School of Chemical and Physical Sciences at Flinders University, South Australia and an independent expert on battery technologies and carbon nanotubes.
"Research has shown vertically aligned – or even just well distributed – carbon nanotubes have far greater properties than randomly placed carbon nanotubes," said Dr. Shearer. "I am not surprised a x10 in conductivity is possible. Controlling the placement of carbon nanotubes is really the way to unlock their potential. The issue in commercialization is the cost associated with producing aligned carbon nanotubes. My guess is the cost would be much more than x10."
We put the question of cost to Nawa. "The million dollar question!" said Boulanger. "Here's a million dollar answer: the process we're using is the same process that's used for coating glasses with anti-reflective coatings, and for photovoltaics. It's already very cheap."
"In high volume, like those processes, yes," added Nawa CEO Ulrik Grape. "We are firmly convinced that this will be cost-competitive with existing electrodes."
"Just to give you some numbers," continues Boulanger, "the cost for depositing anti-reflective coating inside a PV panel is a few cents per square meter. It's the same, we just deposit our material, because we've mastered the process. The growth rate for vertically aligned carbon nanotubes is known as being very, very fast. We can grow vertically aligned nanotubes up to, let's say, 100 microns per minute. It needs only one minute in the furnace. We've scaled this process on very large surfaces, and with a process that works at atmospheric pressure, at lower temperature, we can do it a little bit like making a newspaper. Not that fast, but almost the same idea."
The company has moved past its pilot unit and now has a full production unit up and running, supplying vertically aligned carbon nanotubes for its ultracapacitor devices. Nawa says the electrode technology is more or less agnostic; it can be used on cylindrical cells or flat cells of all sizes.
And it doesn't have to be lithium-ion, either. The company has developed processes to make the nanotubes more compatible with a range of active materials including silicon, nickel-manganese-cobalt and sulfur chemistries, and some other more exotic ones it's exploring with specific cell manufacturers.
In some cases, Nawa says, it eliminates issues that have been holding back certain other battery chemistries. Silicon-based batteries, for example, could offer around twice the energy density of lithium-ion, but the active material grows to four times its size as it's charged and shrinks back again as it discharges, causing mechanical issues that lead to cracks. As a result, you might be lucky to get 50 charges out of a silicon battery before it dies.
Deposit that silicon in tiny blobs all over those carbon nanotubes, says Boulanger, and not only do they have more space to expand into, they have a highly rigid structure constraining them. "Nanotubes are unbreakable," he says. "Unbreakable. Any expansion is lateral, not on the electrode thickness. And the nanotube structure acts like a cage. For silicon, people believe the solution is to create a core/shell nanoparticle where the expanding, contracting silicon is constrained inside a conductive carbon shell. That's today the holy grail of silicon batteries, that's exactly what Sila Nanotechnologies is doing, for instance. We're doing exactly the same, but instead of having core/shell, we have a kind of cage, a mesh cage."
If this technology makes silicon viable, then boom – you can double the energy density again to something around six times that of today's lithium batteries, while potentially dropping the price significantly since you're eliminating expensive, rare lithium metal from the equation.
Boulanger gives another example of a chemistry the team's been working with under NDA for another manufacturer, one that's known to be unstable and to suffer from significant expansion issues. He says that early tests have shown a tenfold increase in the battery's lifespan. "This brings that chemistry," he says, "from something that is really a niche application, to something that could be a mass application."
So when will we see these new high-density beasties on the market? "We expect," says Grape, "that part of this technology can be in product and on the market by 2022. You could call it the simpler version in 2022, and then from 2023 onwards, with all the attributes attached to it. We have to work with the lithium companies. We have certain knowledge on it, but they have their own twists to the technology, be it lithium-sulfur, lithium-silicon or advanced versions of the NMC material that's kind of standard in the market today, or going solid-state with more lithium-metal-based batteries or whatever. So we do our part, but then we also collaborate with them, and so it will depend on their timing coming onto the market."
Moving to these electrodes, Grape and Boulanger say, will require battery companies to make some fairly considerable changes to the early stages of their manufacturing processes prior to cell assembly. But such dramatic performance multipliers without a price penalty or any changes to battery chemistry will surely make these things tough to compete against.
Nawa's first large-scale customer is French battery manufacturer Saft, which is partnering with PSA and Renault as part of the European Battery Alliance to develop EV batteries for the brands under those umbrellas. The company is also speaking to a number of car companies directly, as well as other battery manufacturers supplying the EV space.
As revolutionary as such an energy and power density boost would be for electric cars, motorcycles, ebikes and other emerging ground transport modes, this would obviously also represent a huge potential leap forward for the electric aviation space, in which the weight, energy density and slow charging times of today's lithium batteries are currently putting huge restraints on range and commercial viability for zero-emissions aircraft.
Check out an explainer video below.
We thank Dr. Cameron Shearer for his assistance formulating questions for this interview.
Source: Nawa Technologies