AUTONEWS

Mercedes tests solid-state batteries made by Factorial Energy 

Auto and battery manufacturers have been pursuing solid-state batteries, but to no avail. Mercedes has announced that it is already on the road testing this technology, which reduces price and increases autonomy.

When it comes to electric vehicles, solid batteries are the future, as they promise not only to reduce costs and fire risks, but also to increase the capacity to store more energy and support a greater number of charge/discharge cycles, thus increasing the battery's longevity. And although scientists often claim that accumulators with this technology are just around the corner, the reality is that it has not yet been possible to mass produce them. But as “hope is the last thing to die”, Mercedes announced the start of long-term tests with this type of accumulator, using cells manufactured by the North American company Factorial Energy.

If the battery is the most expensive and heaviest part of any electric vehicle that uses them to store energy, solid-state batteries are seen as the Holy Grail of this technology. In essence, they replace the liquid electrolyte that is traditionally used in the cells that make up the battery pack, within which the lithium ions move between the electrodes (cathode and anode) during charging and discharging operations, with a solid electrolyte, a liquid that, unfortunately, is volatile and flammable. The advantages of solid electrolyte — a type of conductive glass — are that it does not cause leaks that can trigger fires in the event of violent impacts or accidents, it allows for charging with higher power, as it is less prone to heat up and can withstand higher temperatures, and it also guarantees a greater number of charge and discharge cycles, increasing the battery's useful life. At the same time, these solid electrolyte accumulators will be cheaper to produce, 40% lighter and have greater energy density, that is, they store greater amounts of energy for the same size or weight, guaranteeing 25% more autonomy without needing to resort to a larger battery. This means increasing the range of a compact electric car with a small battery from 400 to 500 km, or the range of a model with a more generous battery capacity from 600 km to 750 km. Portuguese researcher Maria Helena Braga explains better than anyone the advantages of this solution in this article.

Mercedes has equipped an EQS with solid batteries from Factorial Energy, which guarantee 25% more autonomy, thanks to an energy density of 450 Wh/kg, which suggests the possibility of the brand's models traveling greater distances between charges. Thus, a Mercedes EQS 450+ that today announces a range of 800 km in WLTP, with a conventional battery with 125 kWh of gross capacity (and 118 kWh useful), can now announce 1000 km with the new solid batteries with the same capacity.

The EQS equipped with solid-state batteries will continue to carry out a series of tests in various types of situations and under real-world conditions of use in order to confirm the efficiency data already obtained in the laboratory. Tests will continue, including those related to charging, without it being revealed which power levels will be used. They will likely be larger than the current 350 kW of Ionity stations — perhaps approaching the 1000 kW that Tesla uses in its Semi — which is currently the most powerful on the market for light vehicles.

In addition to Mercedes, Factorial Energy works with brands from Stellantis and the Hyundai/Kia group. The North American company remains faithful to its original objective of starting to sell this type of accumulator by 2030.

Testing of the solid-state battery began with laboratory evaluations at the end of 2024. In February 2025, the first EQS equipped with the new technology was put through road tests. The program includes different usage conditions to evaluate the battery's performance, durability and safety in real-world situations. Initial simulations indicate that the new technology could offer significant advantages compared to traditional batteries. In the coming months, Mercedes-Benz will continue testing, collecting data on battery performance in different temperatures and driving scenarios. The results will determine the viability of large-scale production and the possible introduction of the technology in future models.

Partnership with Factorial Energy...The collaboration between Mercedes-Benz and Factorial Energy began in 2021, with the aim of developing a new generation of solid-state batteries for electric vehicles. Factorial supplied the first test cells in 2024, enabling Mercedes-Benz to begin in-house testing and integration into the EQS. Factorial's FEST® technology is based on a solid electrolyte, allowing the use of metallic lithium anodes for greater energy efficiency. The research advances aim to improve the energy density and safety of batteries, reducing production costs and facilitating application in electric vehicles in different segments.

Prospects for the future...The introduction of the solid-state battery could represent a breakthrough in automotive electrification, with direct impacts on the autonomy and efficiency of electric vehicles. Mercedes-Benz will continue to invest in the development of this technology, seeking to reduce the challenges associated with large-scale production. The expectation is that new testing phases will be carried out over the next few years, ensuring the reliability of the system. If the results are positive, the commercial adoption of solid-state batteries could occur in the next generation of electric vehicles, bringing benefits to consumers and the automotive industry.

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