Amprius Says Higher Battery Discharge Rate Boosts Electric Aviation

Battery manufacturer Amprius Technologies says it has achieved a new breakthrough in battery technology for electric aircraft and road vehicles with its creation of a new ultra-high-power, high-energy lithium-ion battery that the company claims will provide “unmatched propulsion power and energy.”

The company’s batteries, which are made with silicon nanowire anodes, offer higher energy densities than traditional lithium-ion batteries, most of which are made with graphite or carbon-based anodes. Silicon anodes can store up to 10 times more lithium atoms and therefore provide a significantly higher charging capacity than other types of lithium-ion batteries. 

With its latest product, which the California-based company announced August 3, Amprius has developed a silicon-anode lithium-ion battery that packs an energy density of 400 Wh/kg while simultaneously touting an impressively high discharge rate of 10C. Amprius says the new battery can charge from empty to 80 percent in under six minutes. 

For comparison, the batteries that power electric cars today have peak discharge rates of around 5C. The so-called “C-rate” represents the rate at which a battery discharges relative to its maximum capacity. A battery with a 10C rating will fully charge and discharge in half the time it would take a battery with a C-rate of 5C. 

This new battery could be used for applications like eVTOL aircraft as well as electric road vehicles. According to Amprius, it could enable electric cars to accelerate from 0 to 60 mph (97 kph) in 1.5 seconds—faster than any electric vehicle on the market today. 

“Commercial opportunities in electric mobility are profoundly impacted by their power and energy requirements,” said Amprius CEO Kang Sun. “Our new cell delivers impressive specific power and energy density performance, approximately 200 percent higher than traditional graphite cells, while achieving a 10C discharge rate, significantly expanding application possibilities and driving cost-effectiveness.”

Amprius says the combination of its batteries’ high energy and power densities reduces both their weight and volume. For electric vehicles, that means more range, fewer trips to charging stations, and less downtime spent charging. According to Amprius, the new battery has a power density of 3,500 W/kg in standard discharge conditions and a maximum power of 4,400 W/kg at lower depths of discharge (i.e., when battery charge levels are low).

The new 10C, 400 Wh/kg batteries are expected to hit the market in 2024, and Amprius says it will have samples available for prospective customers by the end of this year. In addition to the 10C, 400 Wh/kg battery, Amprius has several other high-performance lithium-ion batteries that are already commercially available with energy densities ranging from 380 to 500 Wh/kg. 

The company is already providing battery cells for several drone applications, and it intends to offer its products to companies developing larger electric aircraft. In October 2022, Amprius began working with British defense contractor BAE Systems to develop batteries for electric aircraft and other unspecified defense technologies. Just last month the partners announced that batteries developed by Amprius had successfully powered a stratospheric drone during its first flight trial. 

That aircraft was the PHASA-35, a high-altitude pseudo satellite (HAPS) designed by BAE subsidiary Prismatic. The PHASA-35 is a solar-electric drone that uses solar power to charge its batteries, which are supplied by Amprius. During its first flight, the aircraft soared to altitudes above 66,000 feet, reaching the stratosphere before safely landing at its test site in New Mexico. 

In addition to its work with BAE, Amprius has established partnerships with a handful of players in the electric aviation and defense industries. An Amprius spokesperson told FutureFlight that the company is working with Teledyne FLIR, a subsidiary of Teledyne Technologies, to power uncrewed aerial systems (UAS) with defense and security applications. Airbus subsidiary Aalto has also been using Amprius batteries to power its autonomous HAPS, called Zephyr

The spokesperson added that Amprius is preparing to supply “commercial-level shipments” to California-based UAS manufacturer AeroVironment in support of the company’s Switchblade 300 Block 20 loitering missile system. “There are also multiple projects ongoing with the U.S. Military, including developing safe cells for wearables and high-energy cells for other defense applications,” they said.


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