Mercedes-Benz is widening its push into solid-state batteries through a new agreement with Taiwanese battery developer ProLogium. Announced on September 24, 2026, the deal gives Mercedes priority access to evaluate ProLogium’s newest Gen4 lithium-ceramic cells, putting the automaker near the front of the line as the technology moves toward automotive testing.
The significance goes beyond another laboratory partnership. Mercedes and ProLogium have worked together for nearly a decade, while ProLogium has been trying to prove that its battery designs can move from promising test results into repeatable industrial production. The new arrangement does not guarantee a Mercedes production vehicle, but it brings the companies into a more serious validation phase where electrical performance, heat behaviour, safety and vehicle suitability will face detailed scrutiny.
Priority Access Is Important, but It Is Not Yet a Supply Deal
Mercedes-Benz and ProLogium have signed a joint testing agreement covering the battery developer’s latest Gen4 Superfluidized Inorganic Next-Generation Lithium Ceramic cells. Under the arrangement, Mercedes receives priority access to the technology for evaluation. The cells are expected to undergo electrical, thermal and safety testing both at Mercedes-Benz facilities and through specialized outside testing institutes. Those results will be used to determine whether the technology is appropriate for potential future vehicle applications.
That wording is important. Neither company has announced a production vehicle using the Gen4 cells, a firm commercial order, an annual supply volume or a customer launch date. Priority access effectively gives Mercedes an early opportunity to understand how the cells perform under the demanding conditions required by an automaker before decisions about production can be made. For ProLogium, meanwhile, having a major global manufacturer perform this level of evaluation can provide valuable feedback about what still needs to change before a battery designed in a laboratory and factory environment is ready for a mass-produced car.
Gen4 Targets More Than Just Higher Energy Density
ProLogium describes Gen4 as a fully inorganic battery platform built around a non-flammable inorganic electrolyte, ceramic separator technology and what the company calls an Active Safety Mechanism. The objective is to combine several characteristics that battery engineers often struggle to deliver simultaneously: high energy density, strong power output, fast charging, low-temperature capability, safety, manufacturability and eventually a competitive cost structure. Mercedes’ testing program should help establish how those characteristics hold up outside ProLogium’s own development environment.
Solid-state batteries attract considerable attention because replacing conventional flammable liquid electrolytes can potentially improve safety while enabling battery architectures with higher specific energy. That could allow an EV to travel farther without simply installing a heavier battery. Yet academic research also shows why commercializing the technology has taken so long. Solid electrolytes introduce difficult electrode interfaces, mechanical stresses, manufacturing challenges and possible lithium-dendrite problems. Good laboratory performance therefore does not automatically translate into durable automotive cells. Mercedes will be testing not simply whether Gen4 works, but whether it can work predictably enough for an automotive platform expected to survive years of charging, temperature swings and daily driving.
ProLogium Has Already Put Its Gen3.5 Cells Into Production
The timing of Mercedes’ agreement is notable because ProLogium announced another manufacturing milestone only weeks earlier. On September 2, the company said its Gen3.5 Lithium Ceramic Battery had entered mass production at its Giga-level manufacturing facility in Taiwan. ProLogium reported that a third-party TÜV test of a large-format 185.4-Ah cell measured gravimetric energy density of 381 Wh/kg and volumetric energy density of 903 Wh/L. Those are cell-level figures, rather than complete battery-pack specifications, but they illustrate the energy-density potential ProLogium is attempting to industrialize.
ProLogium also said UL Solutions tested the cell using China’s GB/T 43568-2026 methodology. According to the company, the cell lost less than 0.05% of its weight during six hours under vacuum at 120°C, compared with the methodology’s 0.5% maximum threshold used for all-solid-state classification. Gen4 takes a different chemistry approach, but ProLogium says it retains much of the existing cell architecture and manufacturing platform. The company estimates roughly 10% of its current Giga-level production equipment would require modification to build Gen4 cells. If that estimate proves accurate at scale, it could reduce one of solid-state technology’s biggest commercialization barriers: rebuilding factories every time the chemistry changes.
Mercedes Is Already Testing Another Solid-State Battery on the Road
ProLogium is not Mercedes-Benz’s only solid-state battery program. The automaker has also been working closely with U.S.-based Factorial Energy. Mercedes integrated Factorial lithium-metal solid-state cells into a lightly modified EQS development vehicle and began public-road testing in February 2025 after earlier laboratory and test-bench work. Engineers from Mercedes-AMG High Performance Powertrains, the company operation closely associated with its Formula 1 expertise, helped develop the battery system alongside Mercedes’ passenger-car engineers.
That project has since produced a high-profile real-world result. In August 2025, the experimental EQS travelled 1,205 kilometres from Stuttgart, Germany, to Malmö, Sweden, without stopping to recharge. Mercedes said the vehicle arrived with another 137 kilometres of indicated range remaining. The company had previously said the prototype battery could provide up to 25% more electric range than a comparable conventional EQS battery of similar weight and size. Those figures belong specifically to the Factorial program and should not be transferred to ProLogium’s Gen4 cells. Instead, they show that Mercedes is pursuing multiple solid-state routes and has already developed experience integrating unfamiliar cell technology into a functioning vehicle.
The Dunkirk Factory Could Determine How Quickly Gen4 Can Scale
Even an impressive battery cell is of limited value to a global automaker if it cannot be produced consistently in large quantities. ProLogium’s industrial strategy therefore matters almost as much as its chemistry. Its Taoke Gigafactory in Taoyuan, Taiwan, is being used for GWh-scale manufacturing validation, automotive sample production and demonstration programs. The company says it has shipped more than 2.4 million cells across different applications since commercial production began in 2013, including thousands of automotive samples.
Europe is the next major step. ProLogium broke ground on its Dunkirk, France, battery project in February 2026 after establishing an R&D centre in Paris-Saclay in 2024. The latest company plan gives the Dunkirk site a maximum designed capacity of up to 44 GWh annually, although that figure represents the site’s longer-term potential rather than immediate output. Its first phase is designed to reach 4 GWh of annual capacity, progressively, by 2030. That timeline helps explain why Mercedes’ current agreement focuses on testing rather than immediate vehicle supply. The technology may be advancing quickly, but industrial-scale European availability still requires years of factory execution.
Solid-State Batteries Are Entering an Extremely Competitive Market
ProLogium is not trying to commercialize Gen4 in a market standing still. Conventional lithium-ion technology continues to improve while manufacturing costs fall. The International Energy Agency reported that EV battery deployment reached about 1.2 TWh globally in 2025, nearly 30% higher than a year earlier and more than seven times the level recorded in 2020. At the same time, average battery prices declined by about 8% during 2025 as manufacturers improved production efficiency and competition intensified.
Chemistry is also shifting toward cheaper alternatives. Lithium iron phosphate batteries accounted for more than 55% of global EV battery deployment in 2025, according to the IEA, and average LFP pack prices were more than 40% lower than nickel-manganese-cobalt alternatives. That creates an awkward commercial challenge for companies developing more advanced batteries. A next-generation cell cannot succeed only because it delivers impressive energy density. Automakers need to know whether the extra performance is worth the cost, whether production yields can remain high and whether factories can generate enough cells consistently. ProLogium’s emphasis on using much of its existing manufacturing platform for Gen4 appears designed specifically to address that problem.
Mercedes Still Has Several Hurdles to Clear Before Customers See Gen4
The new agreement puts ProLogium’s cells into an important validation stage, but the path between priority testing and a showroom Mercedes remains substantial. Engineers will need to understand how the cells behave across repeated charge-discharge cycles, different temperatures, high-power operation and abnormal safety conditions. Pack designers must also determine cooling requirements, structural support, cell expansion behaviour, electronic controls and how the technology interacts with the rest of a vehicle. Automotive qualification demands consistency across thousands or eventually millions of cells, not simply impressive performance from individual samples.
Solid-state battery research repeatedly shows that interfaces, manufacturing reproducibility and mechanical behaviour remain major challenges even when the underlying chemistry looks promising. That makes Mercedes’ access valuable because an automaker can expose a new cell to conditions far beyond a developer’s headline specifications. For now, no Mercedes production model, purchasing commitment or launch timetable has been announced for ProLogium’s Gen4 technology. What has changed is that Mercedes will get an early, detailed look at whether one of the industry’s more ambitious solid-state platforms is capable of moving from promising cells toward something that can realistically power a future passenger vehicle.
