Amprius Technologies, Inc. has announced that an independent third-party testing lab has validated the company’s 390 Wh/kg polymer electrolyte cell by successfully passing the nail penetration test.
Such cells are being tested for various applications by the U.S. Army, including for use within soldiers’ central power source as the Conformal Wearable Battery (CWB). The CWB integrates into a soldier’s vest and powers critical communications and navigation equipment.
The test is used to determine the feasibility of a specific product in combat scenarios. Cells tested in accordance with 184.108.40.206. of the MIL-PRF-32383 (Military Performance Specification) shall not burn or explode, and the external temperature of each test sample shall not be greater than 338°F (170°C) when penetrated by sharp objects.
When conducting the test, a 0.113-inch diameter stainless steel nail is driven through a fully charged cell at a prescribed speed. The cell is deemed to have passed if there is no smoke or flame following the nail penetration.
Amprius’ polymer electrolyte prevents the penetrating nail from creating a low resistance short circuit, as indicated by the minimal increase in the cell temperature after penetration and only a small decrease in cell voltage. After nail penetration the cell is still functioning and providing power, a critical capability for soldier wearable batteries.
In October 2021, Amprius was awarded a contract by the U.S. Army to develop 100% silicon anode lithium-ion batteries. The 18-month rapid prototyping effort includes design, development, and validation of state-of-the-art, high energy density lithium-ion batteries to be used in various applications by the U.S. Army, including the CWB.
A purchase order for thirty battery packs has been placed by the U.S. Army for capability demonstration.
“As we work toward higher production capacity, the successful passing of this nail penetration test is a significant step in the progression of our technology and product development,” said Dr. Ionel Stefan, CTO of Amprius. “We have a unique opportunity to provide a significant energy density performance increase of nearly 100% – doubling the run-time for all mobile-powered devices without increasing the overall weight of wearable batteries for our U.S. Army soldiers.”