Sometime in 2026, a small fleet of Dodge Charger Daytona EVs will roll onto public roads carrying battery packs that no production car has used before. Stellantis confirmed earlier this year that it plans to equip demonstration vehicles with solid-state cells, a next-generation battery design that replaces the flammable liquid electrolyte inside today’s lithium-ion packs with a solid material. The company and its development partner, Factorial Energy, have framed the technology as a major step toward batteries that resist catching fire.
If the fleet performs as hoped, it would mark the first time solid-state cells have been tested in a production-intent passenger vehicle on real roads under real driving conditions. That distinction matters. BMW ran prototype solid-state cells from Solid Power in modified iX SUVs during 2023 and 2024, but those were engineering mules, not vehicles built on a platform headed for dealer lots. The Charger Daytona is already in production with conventional lithium-ion packs, which means the solid-state variant could, in theory, move toward commercial sale faster than a clean-sheet design.
The promise is significant. The stakes are just as high. Peer-reviewed research and federal safety standards raise pointed questions about whether “resists catching fire” holds up under the stress of daily driving, fast charging, and crash forces that no lab simulation can fully replicate.
Why solid-state batteries are supposed to be safer
A conventional EV battery cell contains a liquid electrolyte, typically a lithium salt dissolved in an organic solvent, that shuttles ions between the anode and cathode during charging and discharging. That liquid is flammable. When a cell is punctured, overcharged, or short-circuited, it can enter thermal runaway: a self-reinforcing chain reaction in which rising temperatures cause the electrolyte to decompose and ignite, sometimes spreading to neighboring cells and engulfing the entire pack.
Solid-state cells swap that liquid for a solid electrolyte, often a ceramic oxide, a sulfide glass, or a polymer composite. Because the solid layer does not vaporize or ignite the way organic solvents do, the most common ignition pathway in a lithium-ion fire is removed. Proponents argue this makes catastrophic pack fires far less likely, even in severe crashes.
That argument has real scientific support, but it is not absolute. A 2022 peer-reviewed study published in Joule and summarized by Sandia National Laboratories modeled heat release and failure scenarios for several all-solid-state configurations. The researchers found that some designs can still reach dangerously high temperatures when short-circuited. The study did not conclude that solid-state batteries are unsafe. It concluded that safety depends heavily on the specific materials, cell architecture, and conditions of failure, not on the “solid-state” label alone.
What the federal lab found
Sandia’s modeling work, conducted at a facility that also tests nuclear weapon components and explosive materials, remains one of the few rigorous, independent assessments of solid-state battery safety. The Joule paper used quantitative thermal simulations rather than physical crash tests, meaning its conclusions describe what the chemistry can do under specific failure conditions rather than what it will do in every real-world event.
Key findings included a wide performance spread among electrolyte types. Sulfide-based solid electrolytes, for instance, can release toxic hydrogen sulfide gas when breached, a hazard that oxide-based alternatives do not share. Some configurations modeled in the study reached peak temperatures comparable to conventional lithium-ion cells during internal short circuits. Others performed markedly better, showing slower heat generation and lower peak temperatures that would give occupants and first responders more time to react.
Sandia researchers have emphasized in subsequent laboratory communications that “solid-state” is not a single technology with uniform properties. Behavior under abuse depends on electrode loading, current-collector materials, and the exact solid-electrolyte composition. That nuance tends to get lost in marketing language that treats the entire category as inherently fireproof.
Existing abuse-test protocols, such as nail penetration and overcharge cycling, were developed for conventional lithium-ion chemistries. Whether those same tests capture the specific ways a solid electrolyte can fail remains an open scientific question. Sandia’s technology disclosures highlight the absence of standardized failure-scenario benchmarks tailored to solid-state cells, a gap that regulators will eventually need to close.
Where the regulatory framework stands
Any vehicle sold to American consumers must comply with Federal Motor Vehicle Safety Standard No. 305a, which governs propulsion battery safety after a crash. The standard, maintained by the National Highway Traffic Safety Administration, sets requirements for electrolyte spillage, battery retention, and electrical isolation, according to NHTSA’s published guidance.
FMVSS No. 305a was written around liquid-electrolyte lithium-ion packs. Solid-state cells introduce materials and failure modes the regulation was not originally designed to address. A sulfide electrolyte that releases toxic gas rather than flammable liquid, for example, poses a different kind of post-crash hazard, one the current spillage metrics may not capture.
As of June 2026, no publicly available NHTSA filing or exemption request tied specifically to solid-state cells in the Dodge Charger Daytona has surfaced. That is not necessarily alarming. A demonstration fleet operating under controlled conditions and driven by company personnel may not require the same certification as a mass-market production vehicle. But the regulatory pathway from demo fleet to dealer lot involves compliance steps that have not been publicly documented, and until such filings appear, outside analysts have limited visibility into how Stellantis plans to prove its solid-state packs satisfy existing crash and post-crash isolation rules.
What we still do not know
Several critical gaps remain in the public record:
Thermal-abuse data. Neither Stellantis nor Factorial Energy has released heat-release measurements under FMVSS No. 305a conditions for the solid-state cells destined for the Charger Daytona fleet. Without that data, independent engineers cannot compare the new chemistry’s crash-safety performance against the liquid-electrolyte packs already certified for production EVs.
Cell chemistry. Factorial has publicly described its technology as using a proprietary solid electrolyte it calls FEST (Factorial Electrolyte System Technology), but the company has not disclosed whether the Charger Daytona cells use a sulfide, oxide, or hybrid composition. Chemistry matters enormously. The difference between a sulfide cell that off-gasses hydrogen sulfide and an oxide cell that does not is the difference between two fundamentally different safety profiles.
Fleet size and geography. Stellantis has not specified how many vehicles will be in the demo fleet, where they will operate, or how long the test program will run. A handful of cars driven on controlled routes in mild climates would generate very different data than dozens of vehicles subjected to Phoenix summers and Minnesota winters.
Pack-level engineering. Cell-to-pack integration, cooling architecture, charge-rate limits, and venting paths all influence whether a localized cell failure escalates into a vehicle-scale fire. Even a relatively stable solid-state cell can become dangerous if tightly packed without adequate thermal management, just as a volatile chemistry can be mitigated by conservative pack design and robust containment.
Data transparency. Automakers frequently treat fleet-test telemetry as proprietary. There is no guarantee that charge-discharge cycling data, thermal logs, or minor-collision outcomes will be shared outside Stellantis and its suppliers. If the results stay behind closed doors, the broader industry and the public gain little from the exercise beyond a marketing claim.
How this fits the wider solid-state race
Stellantis is not working in isolation. Toyota has repeatedly stated it aims to begin limited production of solid-state battery vehicles by 2027 or 2028, using sulfide-based electrolytes developed in-house. Samsung SDI has demonstrated prototype solid-state cells and projected commercialization in the latter half of the decade. QuantumScape, a publicly traded startup backed by Volkswagen, has shipped sample cells to automotive partners for testing but has not yet announced a vehicle integration.
What sets the Stellantis program apart, at least on paper, is the decision to put cells into a vehicle that already exists in production form. The Charger Daytona is on sale today with a conventional 800-volt lithium-ion pack. Dropping solid-state cells into the same platform could accelerate the feedback loop between lab results and real-world performance, assuming the data is eventually shared.
For context on the problem solid-state technology aims to solve: lithium-ion battery fires in EVs remain statistically rare. Data from agencies including NHTSA and the National Transportation Safety Board show that EVs catch fire at lower rates per mile driven than gasoline vehicles. But when EV battery fires do occur, they burn intensely, can reignite hours or days later, and require enormous volumes of water to suppress. Even a modest reduction in thermal-runaway risk would be meaningful for fire departments, insurers, and consumer confidence.
What to watch for next
The most reliable signal that solid-state cells are genuinely safer will not come from a press release. It will come from three things converging: independent thermal-abuse test results conducted under standardized conditions, an NHTSA compliance filing showing the cells meet or exceed FMVSS No. 305a requirements, and real-world fleet data covering thousands of charge cycles across varied climates and driving patterns.
Readers can track progress by monitoring NHTSA’s public docket. If Stellantis moves toward selling solid-state-equipped Charger Daytonas to consumers, the company will need to certify compliance, and any such filing would contain the thermal-runaway and post-crash isolation data that independent analysts need to evaluate the safety claim.
Until those pieces fall into place, the strongest available science, Sandia’s 2022 modeling, suggests that solid-state cells are not universally immune to dangerous heat events. Some configurations perform far better than conventional lithium-ion under abuse. Others can still reach extreme temperatures when short-circuited. “Resists catching fire” is better understood as a design goal backed by promising chemistry than as a proven, tested attribute of the specific cells headed for the Charger Daytona’s battery pack.
The demo fleet will eventually generate valuable telemetry: charge-discharge behavior under varied temperatures, vibration stress from road surfaces, and thermal data during fast charging. That information could validate the safety promise or reveal limitations no simulation predicted. For now, cautious optimism is warranted. The physics of concentrated energy storage have not changed. What has changed is that, for the first time, a major automaker is willing to put solid-state cells on public roads in a vehicle consumers can already buy in a different configuration. That is progress. Whether it is proof will depend on what the data shows.
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*This article was researched with the help of AI, with human editors creating the final content.
