EV Batteries With Higher Silicon Content Are Coming: GM Exec

• Silicon anodes are further ahead in development and commercialization than solid-state batteries.
• Battery makers are aiming to increase silicon content to boost driving range and reduce charging times.
• General Motors says the percentage of silicon in EV batteries is expected to increase over the years.  

Smaller in size and better in range and charging performance, that’s the goal everyone in the battery industry seems to be chasing. Automakers and battery companies are exploring several potential solutions to reach that goal. Silicon anodes will be one way to get there.

“The evolution towards silicon anodes is now starting,” George Cintra, the battery R&D director at General Motors, told InsideEVs. “You’re going to see more silicon incorporated into EV batteries because it provides added range and also helps [EVs] fast-charge,” Cintra said.

In an EV battery, the anode is the electrode where lithium ions are stored when the battery is charged. It typically consists of graphite-based materials. Experts say that the anode’s material and design directly impact the EV’s performance and using a higher silicon content can improve that. Silicon-containing anodes have been around for the past few years but in tiny amounts. Now, that is set to increase.

When asked if GM EVs will get silicon anodes by the end of the decade, Cintra said, “We would certainly like to see that. We have a lot of other technologies we’re trying to implement, and silicon is one of those.”

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Silicon anodes can help EV batteries remove some of the inefficiencies that graphite usage brings. According to a study published in the academic journal Science Direct, 50 to 70% of raw graphite gets lost when upgraded to battery-grade graphite, making the process inefficient, increasing material demand and amplifying supply chain problems.

Silicon is a promising alternative because it can deliver better energy density and speed up charge and discharge cycles.

Like several other emerging battery chemistries, scaling up is difficult because it requires highly specialized processes that are slow and energy- and resource-intensive. However, battery makers are working to simplify those processes, and they’ve already seen some success, with more to come.

Last year, Taiwanese battery start-up ProLogium announced at the Paris Motor Show that its 100% silicon composite anode helped it achieve an energy density of 321 watt-hours per kilogram. That’s well above the current industry standards of well below 300 Wh/kg for LFP and NMC packs. As per certification tests, the 55 kWh pack also charged from 5% to 60% in 5 minutes and 80% in 8.5 minutes. The battery maker claimed it can reduce a vehicle’s weight by hundreds of kilograms.

Several American battery start-ups, including Amprius, Group 14, and Sila Nanotechnologies, are also racing to develop silicon anodes.

Sila’s silicon anodes are already installed in the electric Mercedes-Benz G-Class. However, that EV has an EPA range of just 239 miles and can charge from 10-80% in 32 mins on a 200 kW charger. Sila didn’t reveal the percentage of silicon in the G Wagen’s anode. It’s unclear if it’s a 100% silicon anode, which seems unlikely given its charging performance—it could be using a small percentage of silicon in the existing graphite anode to offset its weight and the aerodynamic shortcomings.

They could also help GM’s trucks and SUVs become more efficient. Models like the Chevy Silverado EV and GMC Hummer EV use massive 200+ kilowatt-hour batteries which make them heavy and inefficient. In a recent test by Edmunds, the GMC Sierra EV Denali achieved an impressive 506 miles of range in a real-world test. But the 8,800-pound truck delivered an abysmal efficiency of 48.1 kWh per 100 miles, or 2.0 miles per kWh. Innovations on the battery front may solve that.

“As the new materials come on board, like silicon anodes and the new cathodes, the battery sizes will shrink,” Cintra said. “As volumes increase, the adoption rate will increase, and you will see prices come down.” 

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