Consumers want faster charging and greater range in their EVs. Luckily, the next generation of batteries already exists; they’re just in the process of being industrialized. Solid-state battery makers send increasing quantities of production-intent samples to automakers, and they're set to transform the amount of energy we can store in battery packs. Conventional lithium-ion is far from dead, though. High-silicon anodes keep the liquid electrolyte alive, and the technology is very close to adoption in electric vehicles.
What’s the deal with high-silicon anodes? Well, almost all lithium-ion batteries in cars right now have anodes—part of the battery’s negative terminal—made of graphite, which is really the only anode material that’s ever been used in them. Adding silicon into the mix changes the cell's characteristics considerably, though any additional costs to do so aren’t clear yet.
The big advantage of high-silicon anodes isn’t necessarily much higher energy; it’s much greater power on the charge and discharge cycles. In other words, faster charge speeds and higher power to the wheels for a given battery pack size.
Charge speed is the key innovation. Some companies claim extreme gains in power and energy, but commercially available silicon cells don’t seem capable of massive gains in both areas, at least not yet. So far, it’s more like big gains in one area and modest gains in another.
To be clear, reputable companies like Amprius are putting out cells with increased power and energy versus state-of-the-art graphite cells, but many projections don’t focus on massive energy improvements. If they do, they offer watt-hour per kilogram figures on the cell level using the pouch format. This isn’t isn’t disingenuous but it lacks context. Pouch cells need more pack structure to keep them working optimally. Once they are actually packaged in a vehicle, the energy density isn’t so impressive anymore.
Without going into the datasheets of specific cells, companies like Molicel are seeing energy gains of around 20%, along with impressive increases in power. These figures are still preliminary, but the cells are in the classic 21700 cylindrical format and are expected to hit the market early next year.
Current cells using a modest silicon blend that you can actually buy—like the Molicel P50B—are seeing power and capacities in the range of current high-performance cells but with considerable improvements in cycle life. For reference, Molicel’s current generation of high-power cells are used in the McMurtry Spéirling, one of the fastest production EVs in the world.
The telling trend in silicon cells is that companies involved in the technology often focus on huge gains in terms of power, not energy. Battery capacities aren’t doubling, but the rate at which they can charge and discharge absolutely is. In some cases, it’s far more than doubling, too. In a previous interview, the CEO of silicon anode material manufacturer Group14 told me, “The new cell that [Molicel is] coming out with, the X series, boy, they’re claiming they can charge that from zero to 100% in 90 seconds,” and their 21700 “X Series” test cells are between 2.5 amp-hours and 5.2Ah, which is typical for the format with today’s technology.
Keep this in mind when thinking about silicon anode technology. It will likely arrive before solid-state batteries and reach widespread use in electric cars, but its earl advantages will mostly be in terms of charging, not range. Likewise, as we all know, many headaches to do with charging now aren’t necessarily vehicle-related but infrastructure-related. So it may seem frustrating initially that these new high-tech battery cells don’t seem much better on the road, but that’s only set to improve as the entire ecosystem of electric vehicles improves.
The batteries are finally getting better, but other things will have to catch up, too.
Peter is the Associate Editor at Motor1 and is a lover of most technology, especially on wheels. He got his Industrial Design degree in 2020 and has not used it since. He resides in New Hampshire.
