By Kyle Proffitt
June 30, 2025 | Creating high density battery systems for trucking, rail, planes, and ships presents different challenges than consumer-oriented EVs. At the 2025 International Battery Seminar and Exhibit earlier this year, engineers from Daimler Truck North America, and the Department of Energy shared the most recent developments in high density applications and the race to 1000 Wh/kg energy density.
Daimler Electrifies Trucks
Rianne Schoeffler, Battery Product Developer at Daimler Truck North America, wanted to talk about the electrification of trucks, specifically class 6-8 vehicles. She began by highlighting the integral role trucks play in the world economy, responsible for about 27 trillion ton-kilometers (the product of distance traveled by payload carried) of carriage per year. They lag behind consumer adoption of passenger vehicles when it comes to electrified variants, however, because the requirements are distinct. Class 8 trucks (the big 18-wheelers) cover about 5 times as many miles per year as cars, and million-mile trucks are within the range of normal business. For the batteries, this means they need to hit 4,000 cycles, significantly more than the commonly accepted 1500 for passenger vehicles.
Schoeffler shared stats for the Freightliner eCascadia and eM2 models, which she said have covered more than 1.5 million miles of public roads in the hands of about 50 customers. Those trucks have ranges up to 250 miles. Additionally, in Europe, the Mercedes-Benz eActros 600 has been released with a range of 310 miles. At this stage, these electrified trucks are not meant to replace long-haul sleepers. They typically require 60-90 minutes for recharging. Megawatt charging can reduce this time to about 30 minutes, but these combinations just don’t match diesel yet. Diesel trucks can hold 300 gallons of fuel and cover 2,000 miles before a 15-minute refueling stop. For now, these electrified trucks fulfill a need primarily as regional or short-haul delivery vehicles.
To get 300-mile range vehicles, the battery packs on these class 8 regional delivery vehicles need to be on the order of 600 kWh, about 10-fold more energy than many EVs. Trucks are also meant to be used as constantly as possible, spending about 75% of time on the road, unlike 5% for passenger EVs. This can actually be advantageous as the battery temperature profile stays more regular.
LFP in trucking
Schoeffler said they’re focused on the total cost of ownership for customers, which centers around longevity and safety. With those ideas in mind, she sees LFP as a strong contender in truck electrification going forward. With LFP, “you can basically use 100% depth of discharge every time without really compromising the durability of the cell,” she said. The eActros 600 uses LFP batteries.
LFP is of course lower energy density than NMC, but some tweaks can improve this. Schoeffler highlighted that adding manganese to the cathode to make LMFP can increase energy density up to 23%. “In the future, we think we can increase manganese content in the LMFP and get to even higher energy density,” she said. Another option is blending LFP with NMC to get the best of both worlds. She said that adding 20% LFP can have a dramatic effect on safety, while maintaining the higher energy density associated with NMC. However, “we will need both components optimized,” she said.
With regard to form factor, Schoeffler favors hardcase prismatic cells for heavy duty trucks, due to their robustness and the ease of module design.
Putting money behind the bet, Daimler truck has a joint venture with Accelera and PACCAR, into Amplify Cell Technologies, a 21 GWh factory located in Marshall County, Mississippi, to accelerate commercial LFP battery cell production in the U.S. They are set to begin production in early 2027.
ARPA-E Pushes for 1000 Wh/kg Batteries
Halle Cheeseman, Program Director at Advanced Research Projects Agency-Energy (ARPA-E), gave a vision for batteries pushing the envelope for the electrification of planes, trains, and ships. He described his group as “the disruptive arm of the DOE,” saying, “we pursue possibilities, we embrace high risk, we try and find those outliers in technology that can be transformational in the world we live in.”
They’ve developed a program called Propel-1K (Pioneering Railroad, Oceanic and Plane Electrification with 1K energy storage systems), and the goal is to create complete systems (not just at the cell level) that have 1000 Wh/kg energy density.
The Propel-1K program began, Cheeseman said, with some basic calculations about how far a regional electrified aircraft could travel, as a function of the energy density of on-board batteries. For some of our state-of-the-art 200 Wh/kg batteries, you’re limited to about 200 miles. “You don’t get to something that you could consider a regional range, until you get to 1000 Wh/kg,” he said. With that density, he showed projections that full-electric planes could cover about half of all regional flights in the U.S., with the other half covered by hybrid solutions. With narrow body aircraft, such as 747s, “maybe 2/3 of the regional missions flown by those planes, not the coast to coast or long distance missions, could be electrified if you had 1000 Wh/kg solutions,” he said.
This energy density would also enable railway electrification. Cheeseman showed an example of a trip from Kansas to Los Angeles that would require 45 train cars filled with current technology batteries to support the trip, whereas the number could reduce to 6 train cars at 1k energy density. (Further improvements occur with battery swaps along the way). Finally, ships. Based on calculations, “with a 1k solution, we would be able to electrify everything operating in US territorial waters,” Cheeseman said.
If You Fund it…
ARPA-E aims to reach this 1k density by providing funding and direction. “If at the end, 10% of the companies we fund are successful, we consider that a success rate for our agency,” Cheeseman said.
Funding for the program is split into two phases. The first phase, Cheeseman said, is to “just give us a reason to believe,” and that’s worth up to $1.5 million per team in funding. This stage involves designing the prototype. Phase two is to actually go build the prototype, and this round will be worth up to $5 million per team.
ARPA-E has provided some suggestions for making these leaps in energy density, such as not being worried about high temperature. He pointed out that jet engines run at 1500 °C, “and we strap them to the wings of a plane.” Additionally, an issue like self-discharge that might rule out a battery for EV use may not be an issue in a battery that experiences continuous or nearly continuous use. He also suggested we consider swapping or mechanical recharging, pointing to the example of the company Electric Fuel, which created swappable zinc-air batteries for German post office vans and electric buses.
Cheeseman suggested we think of metals as fuels. Looked at this way, jet fuel produces 12 kWh/kg on combustion, but lithium metal is very close at 11.1 kWh/kg. This is a theoretical value based on the reaction of lithium with oxygen. Perhaps we can’t tap into all of that energy, but we only need 19% to meet the Propel-1K goal, he said.
The Big Ideas
“Last year we funded 13 teams,” Cheeseman said. He showed a graphic with projections from these teams as high as 2.7 kWh/kg. Those teams are racing to meet goals by end of December this year, when some will be chosen for phase 2. The underlying technologies include lithium-air, aluminum, molten sodium, and rechargeable LiCFx batteries.
Cheeseman highlighted the LiCFx batteries, an old technology with new advancements. These were developed as single-use batteries with energy density in the >700 Wh/kg range, but they were not rechargeable. However, work from the University of Maryland found that mixing halides enabled rechargeability and pushed energy density into 1000 Wh/kg territory. In collaboration with WH-Power and SAFT, this group is now projecting bumping density to 2000 Wh/kg.
Cheeseman shared just a few more examples. Wright Electric and Columbia University are working on an aluminum-air, mechanically rechargeable cell projected to 1.4 kWh/kg. The Illinois Institute of Technology is working on a solid-state Li-air battery, using a hybrid ceramic/polymer electrolyte, and projecting 1.2 kWh/kg. A project from Georgia Tech and MIT is using a molten sodium air/water design and projecting 1.5 kWh/kg.
