390 Wh/kg Cell Passes Military Performance Specification Nail Penetration Test

Amprius Technologies’ polymer electrolyte cells have the potential to increase energy density and reduce overall weight of wearable battery cells for US Army soldiers By DA Reporter / 07 Dec 2022
Amprius Cells

Ultra-high energy density lithium-ion battery manufacturer Amprius Technologies 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 to determine the feasibility of a specific product in combat scenarios. 

The cells were tested in accordance with section 4.7.4.4. of the MIL-PRF-32383 (Military Performance Specification), meaning they shall not burn or explode, and the external temperature of each test sample shall not be greater than 338 degrees Fahrenheit (170 degrees Celsius) 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’ innovative 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.

“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 US Army soldiers.”

In October 2021, Amprius was awarded a US Army contract for the development of 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 Army. 

As part of that program, Amprius is building and testing cells for use within soldiers’ central power source, the Conformal Wearable Battery (CWB). The CWB integrates into a soldier’s vest and powers critical communications and navigation equipment.

A purchase order for thirty battery packs has been placed by the US Army for capability demonstration.

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