Mercedes-Benz and ProLogium sign solid-state battery testing deal

The automaker gains priority access to ProLogium's Gen4 ceramic battery cells as the Taiwanese developer advances a 44 GWh European gigafactory and a Nasdaq

By Rowen Brooks Mon, 28 September 2026 AI level 2 of 5

AI level 2 of 5: drafted by our AI editorial assistant from source material our editor chose; fact-checked, edited and signed off by Mark Walker, Editorial Director. What the levels mean

A brightly lit, modern cleanroom shows a large gray automated machine with clear panels, green and blue internal lights, and a conveyor belt extending towards the viewer, flanked by white workbenches along the walls.

Mercedes-Benz and ProLogium have signed a joint testing agreement giving the German automaker priority access to the Taiwanese battery developer's fourth-generation solid-state cell platform. The agreement, announced on 24 September 2026, deepens a partnership that has been running since 2016 and during which Mercedes-Benz has taken a strategic equity stake and secured a seat on ProLogium's board.

Under the deal, ProLogium's Gen4 cells, branded as "Superfluidized All Inorganic" lithium ceramic batteries, will undergo electrical, thermal and safety testing at Mercedes-Benz facilities and at specialist external institutes. The company says the Gen4 platform combines a non-flammable inorganic electrolyte, ceramic separator and a proprietary active safety mechanism with fast-charging capability and improved low-temperature performance. No timeline was given for when test results would feed into a vehicle programme, and no procurement volumes or cell pricing were disclosed.

The technology and the plant

Solid-state batteries (SSBs) replace the liquid or gel electrolyte in conventional lithium-ion cells with a solid material, offering potential gains in energy density and thermal safety at the cost of manufacturing complexity. ProLogium's ceramic-electrolyte approach sits within the broader SSB category alongside oxide and sulphide chemistries being pursued by rivals including Toyota, QuantumScape and Solid Power.

ProLogium claims its Taoke Gigafactory in Taoyuan, Taiwan, has completed gigawatt-hour scale manufacturing validation and is producing C-sample and demonstration-car units. The company broke ground on the first phase of a second gigafactory in Dunkirk, France, in February 2026. That first phase is designed for 4 GWh of annual capacity, targeted for progressive achievement by 2030. At full build-out, the Dunkirk site is designed for up to 44 GWh, which would place it among Europe's larger battery manufacturing sites. The French government and the European Union have both provided support for the project, though financial terms were not specified in the release.

Vincent Yang, founder and chief executive of ProLogium, said the collaboration has moved from early cell development to testing the latest generation of technology for future vehicle applications, adding that the company is "advancing toward large-scale production in Europe and building a manufacturing footprint to serve global markets."

Capital context and market position

ProLogium is pursuing a Nasdaq listing via a business combination with Translational Development Acquisition Corp (ticker: TDAC), having filed a Form F-4 registration statement with the US Securities and Exchange Commission in May 2026. The company expects to list under the ticker PRLG in the fourth quarter of 2026. Mercedes-Benz is described as supportive of both the Dunkirk build and the listing plan. Access to US public capital markets would provide a significant funding mechanism for the European expansion.

The broader SSB commercialisation race is moving from laboratory demonstrations to early-stage industrial production, but the category remains pre-commercial for passenger vehicles at scale. Energy density and cycle-life claims from developers are not yet independently benchmarked at production volumes, and the cost premium over lithium-ion remains a key variable for OEM procurement decisions. European battery policy, including the EU Battery Regulation and state-aid frameworks supporting gigafactory construction, creates a structural incentive for localised supply chains that ProLogium's Dunkirk facility is designed to capture.

For Mercedes-Benz, the testing agreement is a technology option rather than a committed supply contract. The carmaker has previously invested in and partnered with multiple next-generation battery developers, a hedging strategy typical among premium OEMs that cannot afford to bet exclusively on one chemistry before performance and manufacturing data mature. Investors in both companies will watch for the outcome of the Gen4 test programme, any conversion of this agreement into a formal supply deal, and the progress of ProLogium's Dunkirk construction milestones through 2027.