Last month, Stellantis N.V. and Factorial Energy announced the successful validation of Factorial’s automotive-sized FEST (Factorial Electrolyte System Technology) solid-state battery cells, which combine a lithium-metal anode, quasi-solid electrolyte technology, and a high-capacity cathode. Building on Stellantis’ $75 million investment in Factorial Energy in 2021, the achievement is said to mark a significant step forward on the path to bringing next-generation electric vehicle (EV) batteries to market.

Unlike conventional lithium-ion batteries, solid-state batteries offer higher energy density and faster charging. The validated 77-A·h FEST cells demonstrated an energy density of 375 W·h/kg with over 600 cycles progressing towards automotive qualification, a milestone for a large-format lithium-metal solid-state battery. The cells enable a significant reduction in charging time, from 15% to over 90% charge in just 18 min at room temperature. They also deliver high power output with discharge rates up to 4C, supporting greater performance demands in EVs.

“Reaching this level of performance reflects the strengths of our collaboration with Factorial,” said Ned Curic, Chief Engineering and Technology Officer for Stellantis. “This breakthrough puts us at the forefront of the solid-state revolution, but we are not stopping there. We continue working together to push the boundaries and deliver even more advanced solutions, bringing us closer to lighter, more efficient batteries that reduce costs for our customers.”

Stellantis and Factorial are optimizing battery pack architecture to reduce weight and improve overall system efficiency for better integration by closely collaborating on pack design and leveraging the technology. The weight savings directly enhance vehicle range and support more sustainable and affordable EV solutions.

With the achievement, Stellantis will advance its previously announced plan to integrate by 2026 Factorial’s solid-state batteries into a demonstration fleet, which represents the next step toward commercializing the technology and enables further validation and assessment of performance in real-world driving conditions.

Factorial’s scientific, engineering, and AI-driven tools developed the latest electrolyte formulation that allows the battery to perform in temperatures ranging from -30°C to +45°C (-22°F to +113°F). This surpasses previous solid-state limitations and opens the possibility for better performance across various climates.

“Battery development is about compromise,” said Siyu Huang, CEO of Factorial Energy. “While optimizing one feature is simple, balancing high energy density, cycle life, fast charging, and safety in an automotive-sized battery with OEM validation is a breakthrough. This achievement with Stellantis is bringing next-generation battery technology from research to reality.”

We caught up with Huang to dig a little deeper on the latest Factorial milestone.

 

Futurride: Is Factorial’s tech completely solid state, and if not, why? Is pure solid state coming later?

Huang: We offer solid-state battery products. For our validation work with Stellantis and Mercedes-Benz (see latest here), we’re using FEST cells, which are quasi-solid state with a polymer base. This composition allows us to deliver a financially viable product for most consumers while remaining compatible with the current lithium-ion manufacturing infrastructure.

We also have Solstice, an all-solid-state material that represents a major step forward in energy density. It uses a dry coating process with more sustainable manufacturing methods. FEST is ready today; it has already been scaled to automotive-sized cells and is nearing commercialization. Solstice is a longer-term solution that will require further investment in production and testing.

Each product serves different market needs. FEST is a strong fit for EVs, aviation, drones, marine applications, and power tools thanks to its high-power performance. Solstice is well-suited for consumer electronics and stationary energy storage.

 

Futurride: How is the tech better than that from other solid-state battery innovators?

Huang: There’s a lot of noise and competing claims in the industry. We let our data and customer validation speak for us.

Very few players have achieved full-scale automotive validation with public results. Most demonstrations so far involve small cells or limited performance dimensions. This is the first complete customer validation of a solid-state battery cell by a global OEM, and at an automotive cell scale.

We’ve scaled our cells for real-world automotive use. While small cells often deliver high performance, public data usually focuses on those small formats. We stand out by delivering validated performance at a large-format scale.

Most importantly, we’ve released full data showing unmatched results across energy density, cycle life, fast charging, and low-temperature performance. Battery design always involves trade-offs. It’s relatively easy to optimize for one dimension, but balancing all key performance metrics is the real challenge, and that’s where our technology excels.

 

Futurride: Regarding fast charging, battery tech leaders CATL and BYD are claiming much faster charging. How does your technology compare?

Huang: There’s an important distinction in charging comparisons. Our FEST cells go from 15% to 90% state of charge in 18 min. BYD’s figures reflect charging from 0% to 60% in 5 min. That’s impressive, and consumers will be excited about such fast charging. But the trade-off is energy density.

Our solid-state cells deliver much higher energy density than BYD’s battery. Fast charging is a valuable evolutionary step. But solid-state is a revolutionary shift. It tackles range anxiety at its core by increasing how far you can drive, rather than simply reducing charging time. Faster charging still leaves drivers dependent on frequent charging infrastructure. Higher energy density changes the equation.

BYD has also announced a solid-state program of its own, which underscores the importance of where the industry is headed.

 

Futurride: Is the advantage with FEST lower cost, greater energy density, or something else?

Huang: We want to alleviate range anxiety while offering an affordable solution; those are the two most significant barriers to driving consumer adoption of EVs.

Energy density is the natural advantage of lithium metal solid-state because lithium metal is the lightest metal on earth, has the highest capacity as an anode, and delivers higher energy density in a cell. Higher energy density can translate into better range.

It also leads to weight savings (which translates to better range and cost) by eliminating the need for all the supporting infrastructure in active battery cooling systems. On average, state-of-the-art EVs are 1000-3000 lb heavier than combustion engine vehicles, mostly due to the battery and its structural support.

With high-density solid-state batteries, we are able to reduce at least 200 lb at the pack level, and potentially much more at the vehicle level. Generally, each pound removed from an EV saves about $5 for the consumer.