- Current EV battery anodes are composed mostly of graphite. Silicon can potentially store 10 times as much energy as graphite, but it’s less stable, so it isn’t (currently) feasible to build an entire anode out of silicon.
- NanoGraf has developed a way to increase the stability of silicon dioxide, so more can be incorporated into an anode, increasing energy density.
- NanoGraf’s technology can be “dropped into” existing manufacturing processes, so battery makers can increase the silicon content of their anodes without expensive retooling.
- Silicon is an abundant resource, so it has been less affected by supply chain bottlenecks than other critical raw materials such as nickel, cobalt and aluminum. However, establishing domestic sources, and especially processing, is a priority.
Q&A with NanoGraf COO Connor Hund
Graphite, a pure form of carbon, is a critical material for battery anodes. Graphite’s physical structure allows it to store lithium ions, which merrily migrate to the anode when the battery is charged. Unlike cathodes, which can be composed of various combinations of chemicals (cobalt, nickel, manganese, lithium, iron, phosphorus et al), all current anodes used in EV batteries are composed mainly of graphite.
However, there is another candidate for this key position. Silicon is lighter, and can potentially store more energy, than graphite. Some battery designs use small amounts of silicon mixed in with the graphite to improve battery performance, and finding ways to incorporate more Si in anodes is a major focus of battery research.
NanoGraf, a Chicago-based materials developer that was formed in 2012 (under the original name SiNode) has developed a novel silicon-based anode material that it says has the long-term potential to replace graphite-based anodes, increasing both energy and power density while offering excellent cycle life.
In 2021, the company developed a 3.8 Ah cylindrical lithium-ion cell for the US Department of Defense, which the company claims is the world’s most energy-dense 18650 cell. Soon to be in commercial production, the cell is designed to give military personnel more runtime for their electronic equipment. It’s also designed to save their backs—soldiers may carry upwards of 20 pounds of batteries to power communication devices and other vital gadgets.
In 2022, NanoGraf won a $1-million development contract from the DOD to produce a more powerful, longer-lasting 4.3 Ah battery.
Charged recently spoke with NanoGraf Chief Operating Officer, Connor Hund, about graphite, silicon, and the quest for more powerful, longer-lasting batteries.
Charged: You have a new technology, which involves silicon-based anodes. Is it about replacing graphite, or just using less graphite?
Connor Hund: More about using less graphite. Graphite historically has made up the entirety of the anode, but currently, most commercial cells that you find in the market use 5 to 8% silicon oxide in the anode. What we’re able to do with our next-generation silicon anode material is to increase that percentage up to 20, 25, 30% currently, with higher expectations in the future.
Silicon stores 10 times the amount of energy that graphite does, but it’s a fundamentally less stable material, which is why you aren’t able to build the whole anode out of silicon. It’ll fracture and swell over time with too much in the anode, but that’s fundamentally the benefit—you get more capacity in the battery if you’re able to use more silicon in a stable way.
Charged: So, when the ions are stored in the material, silicon expands a lot more than graphite does. What’s the percentage of the volume expansion?
Connor Hund: Swelling can be about 10 to 15% with graphite. It can be north of 50% with silicon, with first-generation silicon oxide materials, and we typically show about a 15 to 20% improvement on that when you use our silicon. It’ll still expand more than traditional graphite, but we’re able to do it in a stable way that fundamentally comes from the way that we’re prelithiating the silicon oxide core. That sort of enables that reaction to happen earlier in the manufacturing process, and that enables a fundamentally more stable material.
Normal anode material will come into contact with lithium within the battery. What we’re doing is injecting lithium into that core initially. We’ve sort of pre-swelled the material already, before we’re putting it into a battery.
Charged: So the volume of the material is already larger, and when the lithium ions go in, that means the expansion is going to be less?
Connor Hund: Yes, that’s a bit of a simplistic way to describe it. You’d have to get the full explanation at the PhD level, but that’s essentially what’s happening.
Charged: Most of our readers are pretty familiar with how batteries work, but take me back a little bit and explain how the lithium ions get stored in graphite and/or silicon during charging.
Connor Hund: The anode is the negative side of the battery, and there’s a lithium-ion flow between the anode and the cathode, which is the positive side. Those are separated by a separator material, or membrane, and when you’re at a full state of charge versus an empty state of charge, that determines which side of the battery those lithium ions are on.
Charged: We know that there are different kinds of carbon, very specific kinds of carbon that are used in anodes. Is that also the case for silicon?
Connor Hund: Yes, there are two main types of silicon—silicon oxide and silicon carbide. And if you look up NanoGraf versus a lot of our competitors, they’re not pairing the silicon with oxygen the way that we are. With ours, it’s the same elements, but it’s protected better, and that comes down to the prelithiation, as well as our surface coating material that we put around that silicon oxide core. And that also protects it from fracturing, swelling, etc.
The beauty of our material is that it drops into existing manufacturing processes, so we’re able to increase the percentage of silicon in the anode, increase the energy density, without changing manufacturing processes, or using expensive input materials that some of our competitors have to use.
No shade at our competitors, because what they’re doing is impactful, but Sila and Group14 would be examples of companies that use silicon anodes, but with a fundamentally different type of architecture, and different materials than what we’re using.
Charged: You also have a proprietary manufacturing process. Can you tell me about that?
Connor Hund: Without disclosing too much detail, we’re able to use a manufacturing approach that’s proven to be scalable in other industries, and what that allows us to do is lower our scale-up risk and our manufacturing risk. If we were to use fully custom equipment, or expensive input materials that have not yet been scaled, those would represent pretty significant manufacturing and scale-up risk. We’re able to avoid doing those types of things.
At the battery cell manufacturing level, there’s an anode slurry that gets mixed, and it could be all graphite, or it could be a blend of graphite and silicon. We’re able to use the same manufacturing processes that they currently use to mix up graphite, or mix in first-generation silicon oxide. We’re able to do that with our material as that silicon oxide input, in the same way, with the same equipment that they’re currently using.
Charged: What’s your business model? Will you be licensing your technology to battery makers?
Connor Hund: We’ll be a materials manufacturer producing our silicon anode material. That’s the first part of it. But we also have a completed battery cell that we’re able to sell on the market—a cylindrical 18650. We’re able to work with cell manufacturing partners to use our material to enable the world’s most energy-dense cylindrical 18650 [at 810 Wh/L and 4.0 Ah capacity]. That’s our initial product that we’re going to market with.
The Department of Defense funded the development of that battery cell, but we’ll sell it commercially as well. It will be in commercial production in Q3 of 2023. We have a new manufacturing facility in the West Loop, Chicago. That’s under construction currently, coming online in the first half of 2023, and that’s where we’ll be housing our manufacturing going forward. We’ve onshored our production to that facility at the pilot scale, and we’re also scaling up production within that facility.
Charged: Are there any other customers you can talk about?
Connor Hund: I can say that premium consumer products are another initial market for our battery cells. I don’t want to go into specific customer names, but you could think about customers that have a desire for long-lasting battery cells for portable products.
The electric vehicle market is definitely the medium-term vision for the company. We’re using premium markets and Defense Department funding to scale up the company into commercial production. Then the future roadmap is to scale up production further, and pursue those more mainstream cost-competitive markets. That’s the roadmap, but it’s probably on more of a three-year time scale to be selling commercially into those EV markets.
Charged: Supply chains are a hot topic these days. Where does the silicon come from?
Connor Hund: Silicon, fortunately, is a very abundant resource, so that’s been impacted less than a lot of other input materials. Certainly, a lot less than you’ve seen on the cathode side—nickel, cobalt and aluminum have all featured massive price spikes and shortages of supply over the last year. We’ve been impacted less than that, which is good, but we still see the need to onshore a North American battery supply chain. We view ourselves as part of that at the anode material level, but I think there’s a lot of important work happening even upstream of that. It’s at the silicon level, but at the graphite level as well. Something like 70-80% of the world’s graphite comes from China, and that’s a huge consideration.
Charged: What countries does most of the silicon come from?
Connor Hund: It’s mostly from Asia today as well. I think the most important point to make, whether it’s silicon or graphite, is that there’s a processing step that has to happen. There’s been a lot of talk in the media about onshoring mining of critical materials, but not as much talk about processing of those materials, and that’s what happens almost exclusively in Asia today. So that’s probably the part that’s even more important to onshore—the refining of those materials.
Charged: I just spoke with a fellow at a company called Graphex, a big graphite producer, and I asked him, “Do batteries absolutely have to have graphite?” He said, “Yes, for the foreseeable future, it’s going to be mostly graphite,” and he cited the expansion issue as an obstacle with silicon.
Connor Hund: We’re not making claims about completely replacing graphite, which is something you see a number of other companies claiming. I would agree with that individual about the importance of graphite going forward. We’ve certainly proven out, and are proving out in a commercial cell that we’re going to be selling on the market, that there will need to be graphite certainly for the foreseeable future in the anode, but it doesn’t need to be 90-plus percent graphite. We think we’ve proven out already the ability to use up to 30 percent silicon in the anode, and we have development work going on to push that number even further.
Charged: And the more silicon you can get in there…
Connor Hund: …the higher capacity, more energy density that you get.
Charged: Is it just energy density, or are there some other performance advantages to using more silicon?
Connor Hund: That’s the primary benefit, for sure. There are things you can tweak to optimize for different capabilities. You can make really high-power cells with silicon, and our material is a good fit for that as well. So you can think about a range from the highest-power cell that doesn’t have a lot of single-charge capacity, but it can output a lot of energy all at once versus the highest-energy density cell, but it can’t release much energy at any given moment. And that’s a continuum. There’s a curve there, and our silicon material enables high-power cells as well as high-energy cells. We have capabilities to move along that range for cells specific to certain user needs. Electric vehicles, actually, most of the potential customers we talk to don’t want entirely high energy. They want some additional power output versus the highest-energy density cells in the world, so that’s something that we talk to them about, moving along that spectrum to fit their needs.
Charged: Your material strictly goes in the anode, right? It will work with any cathode chemistry?
Connor Hund: That’s right. A lot of other companies in this space require novel electrolytes, or only work with certain cathode materials, or…they’ll only work with certain types of cell designs. For us, that’s not the case, and it’s another advantage that we have from a manufacturability perspective.
Charged: What about some of the future technologies that people are talking about? Solid-state batteries, for example?
Connor Hund: There are different types of solid-state battery cells, some that would completely replace the anode, some that wouldn’t, and it depends which company you’re talking about. QuantumScape would say they’re going to replace the whole thing. Solid Power has shifted their approach somewhat, and some others have as well, towards architectures that fundamentally would use anode materials in a similar way, and for which our material would be also a great fit, and a great complement to push their energy density even higher in solid-state batteries.
I don’t want to make a blanket statement for every design, but part of our vision is that our material enhances solid-state batteries the same way that it enhances incumbent lithium-ion liquid-electrolyte batteries.
For more information about graphite, and why it’s a critical component of EV battery anodes, see our Q&A with Graphex CEO John DeMaio.