Paratroopers test CH-47 Chinook capabilities by sling loading their newest vehicle, the Army Ground Mobility Vehicle, August 30, 2019. Photo Credit: U.S. Army
Battery Technology and the Military EV Transition
The global outlook for the electric vehicle (EV) market is promising. Demand is increasing, prices are dropping, and EVs offer numerous benefits for the military from reducing fossil fuel dependence to potential tactical strengths. The Army’s Climate Strategy outlines the intent to employ hybrid field vehicles by 2035 and fully electric field vehicles by 2050. Yet, while transitioning non-tactical fleets to EVs makes sense from an economic and environmental perspective, the lithium-ion battery currently used in most EVs presents several tactical challenges.
There are three primary barriers to widespread EV adoption by the defense community. First, lithium-ion batteries rely on critical minerals that are sourced from a vulnerable supply chain largely controlled by China. Over reliance on Chinese sourcing and processing has been noted in both the National Defense Strategy, and was at least partially responsible for President Biden’s executive order designed to bolster domestic production. Second, the range of lithium-ion batteries decreases when they are exposed to extreme temperatures, such as -15°F and 110°F. This is too limited a scope for tactical military vehicles that need to operate in extreme conditions, such as the Arctic or the Middle East. Third, the need for charging is an issue for tactical mobility; while portable charging and nuclear technology are developing, there is currently no adequate alternative to the Jet Propellant-8 that is used to fuel tactical vehicles.
Additionally, Lithium-ion batteries currently do not have the stability, energy storage, or dependability required for the military’s tactical vehicles. However, there are innovations in rapid charging underway. Solid-state and sodium-sulfur battery technology offer promising solutions that could pave the way to the vision of an electric-powered military.
Solid-state
One potential alternative is solid-state batteries, which boast a higher energy density than lithium-ion batteries. Solid-state batteries resolve concerns with stability, energy storage, and also provide relief for a strained cobalt supply chain while cutting the carbon footprint of lithium-ion batteries by nearly a third. In a solid-state battery, the lithium-ion liquid electrolyte is replaced with a solid electrolyte that improves the thermal stability, energy storage, and charging capabilities, as well as the safety of EV batteries, thus resolving most of the concerns with the standard lithium-ion battery. The improved stability also reduces the safety equipment required by lithium-ion batteries. However, this technology is still at the lab level, and companies project that commercial production will begin in early 2026 at the earliest. Cost is also a barrier for solid-state batteries, with some estimates putting initial costs as high as $800/kwh, whereas to be commercially viable, costs will need to be much closer to $100/kwh. Additionally, it is estimated that solid-state batteries use about 30 percent more lithium than standard lithium-ion batteries. However, they use less cobalt, which is the critical mineral with the most vulnerable supply chain today.
Sodium-ion
Another alternative to traditional lithium-ion batteries are sodium-ion batteries. New chemistry already reduces cobalt in lithium-ion batteries by up to 70%, but sodium-ion batteries also require less cobalt and lithium, creating a less toxic battery. These batteries also provide thermal stability and a long life-cycle and can potentially provide a relatively low-cost and more sustainable form of energy storage. However, these batteries lack the energy density that lithium-ion batteries possess, making current sodium-ion technology only compatible with shorter-range vehicles and light-duty vehicles. As this technology develops, the energy density gap could shrink, providing a sustainable alternative to the standard lithium-ion battery. In the meantime, sodium-ion batteries could be complementary to solid-state batteries to help reduce the strain on lithium supply chains as the world ramps up EV demand.
What Next?
The race for the future of EV batteries is on. The Department of Energy has earmarked $42 million for research labs across the country, including a $5.6 million grant to Solid Power to develop a nickel- and carbon-free solid-state battery. While commercialization could be only decade away, these batteries provide answers to some of the concerns over the suitability of EVs for the military. Yet, as Stanley Darbro, Deputy Director of the Army’s Rapid Capabilities and Critical Technologies Office, pointed out the Army has tactical planning considerations, such as the difficulty of constructing and protecting an electric grid on the battle field, concerns about the placement of batteries on the floors of vehicles, and the need to offboard electricity to run weapons systems. Any comprehensive use of EVs in combat is still several years away, but the current advances in battery technology indicate the promise of EVs for non-tactical, light-duty, and support vehicles.
