Solid-State Battery Pack From ProLogium, Rimac Debuts in Paris

A mockup, a roadmap and a lot still to prove

At the 2026 Paris Motor Show, Taiwanese cell maker ProLogium and Croatian supplier Rimac Technology showed a concept mockup of a battery pack. The two companies have spent roughly a year developing it together, and they presented it as the starting point for building working hardware.12 They formalized the partnership with a memorandum of understanding in September 2025. The next step is a functional battery segment that engineers can use to test thermal management and cell-integration ideas before scaling up to a full pack.15

The headline is modest. A mockup does not store energy, and the companies did not claim it does. Read alongside ProLogium's recent cell-level announcements, though, the Paris display shows where the real bottleneck in solid-state batteries now sits. The question is less whether a better cell can be made and more whether it can be packaged into a car at a cost and reliability carmakers will accept.

What the partners actually announced

The project is built around a pouch cell-to-pack architecture. In this design, cells are placed directly into the pack structure rather than grouped into intermediate modules, which saves space and weight.13 ProLogium supplies the cell technology, and Rimac Technology handles battery systems engineering.3

Daniel Kišić, Rimac Technology's Principal Product Architect, said the company is building a scalable integration technology specifically for solid-state pouch cells. He added that several solutions are being tested in parallel on functional segments, covering heat, swelling, cell integration and overall system design.5 Some of these configurations aim for maximum energy density and smaller, lighter packs, while others aim for higher performance.45 Kišić said a validated pack should cut weight enough that automakers could choose between more energy at the same mass, a smaller pack with the same range, or something in between.5

ProLogium founder and CEO Vincent Yang called the Paris showing the baseline of the collaboration. He said functional segments are already in development.46

The published roadmap has three milestones:

• CES 2027: display of the functional battery segment.12
• Second half of 2027: a full-scale functional battery pack.13
• Second half of 2028: in-vehicle integration and public-road testing.14

Coverage of the announcement was consistent on these dates. It also agreed on a point the companies made themselves: none of these dates is a production commitment.14

The timeline has held, which is worth noting

In a sector known for slipping schedules, the most telling detail may be that this one hasn't slipped yet. In October 2025, Rimac Technology COO Nurdin Pitarevic said the partners were aiming for a first sample battery by the end of 2027, with a B-sample ready for vehicle testing in 2028. He said the goal after that was a battery ready for small-scale production by 2030.9 Those targets line up closely with the roadmap shown in Paris.

Pitarevic was also unusually candid at the time. He estimated that Rimac Technology was about halfway to its goals on safety, range and charging, and that ProLogium was about halfway on the cell.9 He described the target automakers want as a pack of roughly 100 kWh delivering 500 to 600 km of range, with 10-to-80 percent charging in under ten minutes.9 The Paris materials did not repeat those numbers. They focused instead on integration challenges, which suggests the partners are now reluctant to put performance figures on hardware that doesn't exist yet. The 2025 targets are best read as goals the partners have not walked back, not as specifications.

Why integration is now the story

Automotive World's coverage framed the news this way: the roadmap shows integration, not chemistry, now setting the pace for solid-state batteries.4 I think that framing is right, and the details support it.

Swelling management comes up repeatedly in Rimac's comments. It is a known practical problem for solid-state pouch cells, which can expand and contract during cycling in ways that stress a pack's structure.4 Electric Cars Report also listed thermal management, cell swelling, structural integration and vehicle packaging as the problems that separate a good cell from a usable automotive battery.1

ProLogium's own pitch addresses part of this. At CES 2026, the company said its superfluidized all-inorganic cell does not need high external pressure to perform. It argued this simplifies pack design and lowers system cost and weight.12 If that holds up at pack level, it would be a real advantage, because many solid-state designs need heavy clamping hardware that eats into their energy-density gains. The Rimac program looks like the place where that claim will be tested in practice.

The cell side: real production, small volumes

The Paris news follows a busy few months for ProLogium. On September 2, the company said its Gen 3.5 Lithium Ceramic Battery had entered mass production at its Giga-level facility in Taiwan.11 A TÜV report found that its 185.4 Ah large-format cell reached 381 Wh/kg and 903 Wh/L.1113 Separately, UL Solutions tested the cell under China's GB/T 43568-2026 method: six hours under vacuum at 120°C. The cell lost less than 0.05 percent of its weight, well below the 0.5 percent limit for classification as all-solid-state.1115

That certification matters more than it might seem. CarNewsChina noted that the "solid-state" label is applied to an increasingly wide range of designs, so an independently tested classification gives ProLogium's claim more weight.16 There is some tension in the company's own messaging, though. ProLogium has described its superfluidized platform as combining the advantages of solid-state and liquid technologies.10 At the same time, it promotes the all-solid-state classification. Both can be true, but buyers will want to see how the chemistry works in practice, not just the label.

The bigger gap is volume. CarNewsChina reported that the Taoyuan plant's initial operating capacity is 0.5 GWh, with plans to expand toward 1–2 GWh. By its estimate, 0.5 GWh is roughly 6,250 packs of 80 kWh a year.16 The same outlet stressed that 381 Wh/kg is a cell-level figure. Cooling, structure and electronics all add mass, so it does not prove a lighter pack.16 Electric Cars Report raised similar caveats about range, durability, cost and long-term reliability.15 This is exactly the gap the Rimac collaboration is meant to close.

Europe, Mercedes and the capital question

ProLogium is also expanding production in Europe. It broke ground on the first phase of its Dunkirk gigafactory in February 2026. That phase is designed to reach 4.0 GWh of annual capacity, progressively achieved by 2030.11 Reports differ on the site's ultimate size: the company cites a maximum of 44 GWh, while Battery-News reported up to 48 GWh and an investment of about €5.2 billion.1017 Dunkirk has also been delayed before. Automotive News Europe reported in 2025 that French media said its production start had been pushed back a year.9 The current plan, set out at CES 2026, calls for mass production of Gen 4 cells to begin there in 2028 at 0.8 GWh.12

Other partners are moving too. In September, Mercedes-Benz secured priority access to ProLogium's Gen 4 cells under a joint testing agreement. The two companies have worked together since 2016.14 ProLogium says Gen 4 can reach up to 400 Wh/kg and charge from 5 to 80 percent in 6.4 minutes.14 To fund all of this, the company agreed in May to merge with a SPAC, Translational Development Acquisition Corp., and plans to list on Nasdaq as PRLG, subject to approvals.5 Separately, coverage has noted the company promoting AI data centers, aerospace and maritime uses for Gen 3.5, though no data-center customer has been disclosed.19

The read

The Paris mockup is not a breakthrough. It is a credibility exercise. ProLogium needs to show investors, ahead of a public listing, and carmakers like Mercedes that its cells can become working automotive packs. Rimac Technology, a Tier 1 supplier that already works with major automakers and on the Bugatti Tourbillon, gives it a systems partner whose name carries weight.5

The real tests come in sequence: a working segment at CES 2027, a full pack in late 2027, and road testing in late 2028.4 Small-scale production, the 2030 target Rimac described a year ago, comes after that.9 For climate technology, the main lesson is that the hard part of solid-state batteries has shifted from the lab bench to the engineering floor. Swelling, heat and packaging will decide whether these cells end up in cars, and whether that happens soon enough to matter.