All the Information on Solid-State Batteries in Electric Vehicles

The king is dead, long live the king. But wait, we are not there yet—at least not when it comes to batteries for electric vehicles. The conventional lithium-ion battery has not yet reached the end of its lifecycle. The proven technology still offers ample potential for further development. Starting in the middle of the decade, Mercedes, in collaboration with its partner Sila Nano, aims to introduce a significant advancement in lithium-ion battery technology in the electric version of its G-Class SUV. These energy cells are expected to achieve an energy density of more than 800 Wh/l, which is 20 to 40 percent higher than current lithium-ion batteries. Other major OEMs are targeting similar values.

What Are the Advantages of Solid-State Batteries?

But the better is the enemy of the good. By the end of the decade, Mercedes plans to integrate solid-state battery technology into its vehicles. The advantage of these batteries lies in their significantly higher energy density. To illustrate: A lithium-metal anode has approximately ten times the specific energy of the graphite anode used in lithium-ion batteries.

"We expect solid-state batteries to achieve energy densities of up to 1,200 Wh/l," states Mercedes. This promises significantly greater range. But not only that. "With these performance values, new applications for electrification become possible, such as battery-electric flight or solutions for heavy-duty commercial vehicles," explains Peter Fintl, Head of Technology and Innovation at Capgemini Engineering.

The fact that solid-state batteries use inorganic, solid, or ceramic electrolytes arranged in thin layers increases stability and safety. These components are more resistant to heat and damage, making them less flammable. However, solid-state batteries currently function best within a temperature range of 50 to 80 degrees Celsius. This is not ideal for reliable cold-start behavior at very low temperatures. Research is focused on overcoming this hurdle. Once achieved, the advantages of solid-state batteries will outweigh their challenges, significantly increasing vehicle range.

Polymer-Based Solid-State Batteries

As part of the Cell Platform Polymers Project (FB2-POLY), researchers at the Landshut University of Applied Sciences, in collaboration with the Helmholtz Institute Münster, the Helmholtz Institute Ulm, and the Karlsruhe Institute of Technology (KIT), aim to develop new concepts for high-performance and safe batteries using polymer-based solid electrolytes. 

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Landshut University is contributing to the development of a lithium-free anode based on electrospinning technology. Here, the lithium anode forms only during charging, using lithium from the cathode, and dissolves again during discharge. According to researchers, using a lithium-free anode could significantly reduce battery production costs since processing metallic lithium requires complex procedures. From an application perspective, the Landshut team is exploring the possibility of using lamination technology to assemble and connect solid-state batteries with a polymer electrolyte. The goal is to transition this process into mass production.

At the end of the project, researchers aim to provide materials that will enable Germany to become a global leader in battery storage technology. They are working closely with industry partners to develop strategies that will be applied in a pilot manufacturing setting. The researchers are also considering future industrial requirements right from the start.

Nio Announces 150-kWh Battery Pack From Mass Production

According to media reports, Nio has introduced its first mass-produced semi-solid-state battery pack as part of its battery-swapping concept. Currently, the Chinese OEM offers vehicles with two battery options: 75 kWh and 100 kWh. Soon, a new 150-kWh battery option with an energy density of 360 Wh/kg is expected to provide an extended range of up to 1,055 km.

Following its initial announcement in 2021, Nio has now begun mass production of the semi-solid battery, developed by WeLion New Energy Technology. This company also serves as the battery supplier. The exact market release date for the new battery packs remains unclear.

Svolt Develops Sulfide-Based Electrolyte

Chinese company Svolt has assembled its own R&D team to advance solid-state cell technology. Recently, it produced its first batch of 20Ah cells with a sulfide-based solid-state electrolyte, becoming the first Chinese battery manufacturer to demonstrate this type of cell production.

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Werner Beutnagel

Svolt identifies key challenges such as maintaining high conductivity in the solid electrolyte, ensuring long-term stability at interface contacts, and efficiently transferring lithium ions even at high charge rates. The company claims that sulfide-based solid-state cells outperform liquid-electrolyte cells in energy density, charging speed, safety, cycle stability, and temperature resistance.

In abuse tests, such as a 200°C hot-box test and a nail penetration test, Svolt’s 20Ah cells remained intact, whereas traditional liquid-electrolyte cells typically suffer from thermal runaway under similar conditions. Svolt plans to continue expanding its research activities in solid-state batteries and new processing technologies to further develop the foundation for mass production.

BMW Aims to Capture the Solid-State Battery Value Chain

Automakers now see solid-state batteries as an opportunity to catch up with Asian competitors in lithium-ion battery production. BMW, for example, leads the Alano research project, where the German automaker collaborates with the Helmholtz Institute Ulm and other partners to develop innovative EV battery concepts with lithium-metal anodes.

The ambitious goal is to develop a commercially viable solid-state battery while also establishing an entire value chain—from material selection and component manufacturing to cell production, battery scaling for vehicles, and ultimately recycling. BMW has also partnered with Ford and Solid Power to produce solid-state battery prototypes. These cells, boasting an energy density of 390 Wh/kg and 930 Wh/l, can charge up to 80% in just 15 minutes. The first prototype vehicles equipped with these batteries are expected to be on the road later this year.

What VW Is Planning with QuantumScape

In the race for pole position in solid-state batteries, other automakers are not sitting idle. The Volkswagen Group has been the largest shareholder in QuantumScape, a Stanford University startup, for four years now, and new results have recently emerged. Co-founder and CEO Jagdeep Singh announced at Bloomberg’s Green Summit that his company has successfully developed a 16-layer solid-state cell that retains over 80 percent capacity even after 500 fast-charging cycles of 15 minutes each. The key advancement is not only the six additional layers compared to the cell the startup introduced in November 2021 but also the fact that the cells now function at a temperature of 25 degrees Celsius and under air pressure no higher than 3.4 bar.

QuantumScape is prioritizing flexibility in its solid-state batteries. "Our architecture is cathode-independent, meaning we can transition from nickel to iron," Singh explained. The key breakthrough is the ability to pair an iron-based cathode with a lithium-iron anode, which can result in a 50 percent increase in energy density. This flexibility is particularly advantageous given ongoing supply chain challenges. "Regarding cathodes, we face the same supply chain limitations as everyone else," Singh acknowledged.

When Will Toyota Introduce Solid-State Batteries in Passenger Cars?

Toyota is also jumping on the solid-state battery bandwagon, working alongside Panasonic on these next-generation batteries. This project is being handled by their joint venture, Prime Planet Energy & Solutions Inc. The key to their energy storage technology lies in the electrolyte, which in Toyota and Panasonic's case is a phosphorus-sulfur compound. The Japanese automaker plans to release its first vehicle with a solid-state battery in 2025, but it won’t be a fully electric vehicle (BEV)—instead, it will be a hybrid model.

The reasoning behind this seemingly cautious decision is cost. Solid-state batteries are currently significantly more expensive than lithium-ion batteries, which would drive up the price of such a vehicle. Toyota is determined to avoid this. Over time, however, solid-state batteries are expected to become cheaper than today’s lithium-ion cells. Additionally, Toyota views using the technology in a hybrid as a stress test. This will help assess factors such as frequent charge cycles and the impact of operating temperature on the battery.

If these batteries pass Toyota’s rigorous testing, they are expected to go into full-scale production by 2028. Toyota is already working intensively on mass production of solid-state batteries, as the company has announced. The performance data of these batteries is impressive and could solve some of the key challenges in e-mobility: up to 1,200 kilometers (746 miles) of range with a charging time of just 10 minutes to reach 80% capacity. In the long term, Toyota envisions a potential range of 1,500 kilometers (932 miles).

Mercedes Collaborates with Multiple Solid-State Startups

The U.S. startup Factorial Energy is attracting automakers like moths to a flame. In addition to Stellantis and Hyundai, Mercedes is also investing in the Massachusetts-based company. According to Factorial, its engineers have solved the temperature problem, allowing the cells to operate at room temperature.

Expectations are high: "With Factorial as a new partner at our side, we are taking research and development in the promising field of solid-state batteries to the next level. That’s why we are investing a high double-digit million-dollar sum in Factorial," explained Mercedes CTO Markus Schäfer.

However, Mercedes wouldn't be Mercedes if its solid-state battery strategy relied on just one pillar. The second key player in its bid for the future of battery technology is the Taiwanese company ProLogium, with whom the German automaker has been collaborating for some time. Mercedes is investing heavily in ProLogium’s research efforts and has even secured a seat on the company's board. The move makes sense for Mercedes, as ProLogium is, according to the company, the first battery manufacturer in the world to mass-produce solid-state lithium-ceramic batteries. The plan is for ProLogium to open a gigafactory near Taipei by the end of this year, with the first solid-state battery prototypes expected to be tested in Mercedes vehicles in the coming years.

GM Invests Billions in New Battery Technology

The days when GM sat back and watched competitors while relying on its dominance in the North American market are over. The American automaker is actively pushing into the solid-state battery sector. GM CEO Mary Barra has allocated $7 billion to establish a supply chain for next-generation batteries, including solid-state technology. A key partnership in this strategy is with Posco Chemicals, which will build a new factory in Quebec to produce cathode-active materials for GM’s Ultium battery cells.

However, even in the solid-state battery sector, the world remains small. Recently, Posco Chemicals has also invested in ProLogium, raising questions about how the competing interests of OEMs will be balanced. Fundamentally, Hyundai, Stellantis, GM, and Mercedes share the goal of making solid-state battery technology commercially viable. However, that is where their shared interests end. When it comes to competitive advantages and market dominance, the current alliance could quickly fracture, leading to fierce competition as each automaker fights for its own strategic position in the industry.

This article was first published at automotive.eu

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