Powerful Battery Cell Nails Military Safety Test

By Mikayla Easley

Amprius Technologies photo

ARLINGTON, Virginia — A new battery cell could help give soldiers the power they need to run their equipment on the go — without the risk of it exploding if the battery is ever hit.

California-based Amprius Technologies recently announced that the company’s polymer electrolyte cell successfully passed a military-specific nail penetration test conducted by an independent third-party lab. The 390-watt-hour-per-kilogram cell increases a lithium-ion battery’s energy density while simultaneously keeping the weight of the entire battery low, according to a company executive.

“That’s extremely desirable for the Army because now … soldiers have more and more electronics on them so more and more power is needed,” said Ionel Stefan, chief technology officer at Amprius Technologies. “But the battery still needs to have exactly the same [amount of] safety as previous batteries.”

The safety tests demonstrated that the electrolyte cell would not react violently — or at all — if punctured, Stefan said. Furthermore, the battery still worked properly even after being hit, he added.

“Assume that, for example, a soldier’s battery is shot at or penetrated by shrapnel. The soldier probably wouldn’t be in good shape also,” he said. “If the battery still functions, the soldier has time to call for help or an automatic call gets generated by the equipment.”

Amprius’ polymer electrolyte cell is designed to insulate any object that enters it, Stefan explained. During the tests, this prevented the penetrating nail from causing an “internal short circuit” that could lead to a potentially violent reaction and instead allowed the battery to continue operating, he said.

“The higher the energy density, the more difficult it is usually to pass this kind of test because you have more energy released in the same amount of time,” Stefan said. “So that’s why it’s unprecedented to have, first, that kind of battery with such a high energy density, and then also passing the nail penetration test.”

The development and tests of the polymer electrolyte cells are part of a larger, 18-month-long rapid prototyping contract Amprius received from the Army in 2021 to develop the company’s 100 percent silicon anode lithium-ion batteries for the service.

The Army has ordered 30 wearable battery packs integrated with Amprius’ polymer electrolyte cells and silicon anode nanowire platforms, Stefan said.

Topics: Energy

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