By Kyle Proffitt
June 30, 2025 | Developing high-density battery systems for trucks, trains, aircraft, and maritime vessels presents unique challenges compared to consumer-oriented electric vehicles. During the 2025 International Battery Seminar and Exhibit earlier this year, engineers from Daimler Truck North America and the Department of Energy presented the latest advancements in high-density applications and the pursuit of achieving 1000 Wh/kg energy density.
Daimler Electrifies Trucks
Rianne Schoeffler, Battery Product Developer at Daimler Truck North America, discussed the electrification of trucks, particularly class 6-8 vehicles. She started by emphasizing the vital function trucks serve in the global economy, accounting for approximately 27 trillion ton-kilometers (the product of distance traveled and payload carried) annually. However, they lag behind the adoption of electrified passenger vehicles, as their requirements differ significantly. Class 8 trucks (the large 18-wheelers) travel approximately five times more miles per year than passenger cars, with million-mile trucks being quite standard in the industry. For batteries, this necessitates achieving 4,000 cycles, considerably more than the typical 1500 for passenger vehicles.
Schoeffler revealed statistics for the Freightliner eCascadia and eM2 models, which she noted have collectively traveled over 1.5 million miles on public roads, operated by around 50 customers. These trucks can reach ranges of up to 250 miles. Additionally, the Mercedes-Benz eActros 600 has debuted in Europe with a range of 310 miles. Currently, these electrified trucks are not designed to replace long-haul sleepers, as they typically require 60-90 minutes for recharging. With megawatt charging, this duration could decrease to about 30 minutes; however, they still don’t match diesel capabilities. Diesel trucks can store 300 gallons of fuel and cover 2,000 miles before requiring a 15-minute refueling stop. For the time being, these electrified trucks primarily meet the needs for regional or short-haul deliveries.
To achieve a 300-mile range, the battery packs in these class 8 regional delivery trucks need to be around 600 kWh, which is nearly 10 times more energy than many electric vehicles. Trucks are also intended to be utilized as much as possible, spending about 75% of their time on the road, compared to only 5% for passenger EVs. This can actually be beneficial, as it helps maintain a more consistent battery temperature profile.
LFP in trucking
Schoeffler mentioned their focus on the total ownership cost for customers, which revolves around durability and safety. With those considerations in mind, she views LFP as a top contender in truck electrification moving forward. With LFP, “you can essentially utilize 100% depth of discharge every time without significantly jeopardizing the cell’s durability,” she indicated. The eActros 600 employs LFP batteries.
LFP, of course, offers lower energy density compared to NMC, but certain modifications can enhance this. Schoeffler pointed out that incorporating manganese into the cathode to produce LMFP can boost energy density by up to 23%. “In the future, we believe we can elevate manganese content in the LMFP to achieve even greater energy density,” she noted. Another alternative is blending LFP with NMC to obtain the advantages of both materials. She remarked that adding 20% LFP can substantially enhance safety while retaining the higher energy density associated with NMC. However, “we will need both elements fine-tuned,” she emphasized.
Regarding form factor, Schoeffler prefers hardcase prismatic cells for heavy-duty trucks due to their sturdiness and straightforward module design.
Backing this endeavor, Daimler Truck has formed a joint venture with Accelera and PACCAR to establish Amplify Cell Technologies, a 21 GWh facility located in Marshall County, Mississippi, aimed at expediting commercial LFP battery cell production in the U.S. They are expected to commence production in early 2027.
ARPA-E Pushes for 1000 Wh/kg Batteries
Halle Cheeseman, Program Director at the Advanced Research Projects Agency-Energy (ARPA-E), outlined a vision for batteries advancing the electrification of planes, trains, and ships. He characterized his team as “the disruptive arm of the DOE,” stating, “we pursue potential, we take on significant risks, and we strive to discover those exceptional technologies that can be transformative in our world.”
They have initiated a program called Propel-1K (Pioneering Railroad, Oceanic and Plane Electrification with 1K energy storage systems), with the aim of developing complete systems (not just at the cell level) that attain 1000 Wh/kg energy density.
The Propel-1K initiative commenced, according to Cheeseman, with fundamental calculations regarding how far a regional electrified aircraft could fly, based on the energy density of onboard batteries. With current state-of-the-art 200 Wh/kg batteries, you can reach a limit of around 200 miles. “You don’t get to a distance that you could define as regional until achieving 1000 Wh/kg,” he stated. At this density, he displayed projections suggesting that fully electric planes could cover approximately half of all regional flights in the U.S., with the remaining half being managed by hybrid solutions. For narrow body aircraft, such as 747s, “potentially 2/3 of the regional missions operated by those planes, excluding coast-to-coast or long-haul trips, could be electrified if 1000 Wh/kg solutions were available,” he added.
This energy density would also facilitate railway electrification. Cheeseman illustrated an example of a journey from Kansas to Los Angeles that would necessitate 45 train cars filled with current-generation batteries to make the trip, whereas that requirement could shrink to 6 train cars at 1k energy density (further enhancements would occur with battery swaps along the route). Lastly, for ships, Cheeseman remarked, “with a 1k solution, we would have the capability to electrify everything operating in U.S. territorial waters.”
If You Fund it…
ARPA-E intends to achieve this 1k density by offering financial support and strategic guidance. “If, in the end, 10% of the companies we fund succeed, we deem that a favorable success rate for our agency,” Cheeseman stated.
Funding for the program is divided into two phases. The initial phase, Cheeseman explained, aims to “just give us a reason to believe,” with funding available up to $1.5 million per team. This stage encompasses prototype design. The second phase involves constructing the prototype, with this round providing up to $5 million per team.
ARPA-E has provided various recommendations for achieving leaps in energy density, such as embracing high temperatures without concern. He pointed out that jet engines operate at 1500 °C, “and we attach them to the wings of a plane.” Additionally, issues like self-discharge that might exclude a battery from EV usage may not pose a problem for a battery experiencing continuous or nearly constant use. He also proposed considering battery swapping or mechanical recharging, referencing the company Electric Fuel, which developed swappable zinc-air batteries for German postal vans and electric buses.
Cheeseman suggested we think of metals as fuels. Viewed this way, jet fuel generates 12 kWh/kg upon combustion, but lithium metal is remarkably close at 11.1 kWh/kg. This is a theoretical value based on the reaction of lithium with oxygen. While we may not capture all that energy, we only require 19% to meet the Propel-1K objective, he indicated.
The Big Ideas
“Last year we funded 13 teams,” Cheeseman revealed. He displayed a graphic showcasing projections from these teams as high as 2.7 kWh/kg. Those teams are competing to meet targets by the end of December this year when some will be selected for phase 2. The foundational technologies encompass lithium-air, aluminum, molten sodium, and rechargeable LiCFx batteries.
Cheeseman emphasized the LiCFx batteries, an established technology with recent advancements. These were originally designed as single-use batteries with energy densities exceeding 700 Wh/kg, but they lacked rechargeability. However, research from the University of Maryland demonstrated that incorporating halides enabled rechargeability and elevated energy density into the territory of 1000 Wh/kg. In collaboration with WH-Power and SAFT, this group is now forecasting an increase in density to 2000 Wh/kg.
Cheeseman shared additional examples. Wright Electric and Columbia University are developing an aluminum-air, mechanically rechargeable cell projected to achieve 1.4 kWh/kg. The Illinois Institute of Technology is focusing on a solid-state Li-air battery, utilizing a hybrid ceramic/polymer electrolyte, and targeting 1.2 kWh/kg. A project between Georgia Tech and MIT involves a molten sodium air/water design with a projection of 1.5 kWh/kg.
