Starting with lithium ion batteries, researchers played around with “button cells”, which look a lot like watch batteries. Each cell is made up of two electrodes, an anode and a cathode. Between them is a separator soaked in liquid electrolytes. It’s those electrodes that have a tendency to corrode when they react to the electrolytes.
The answer to that problem, they discovered, is a substance called “tris (hexafluoroisopropyl) phosphate”, or HFiPP, because the Army likes acronyms.
The Army’s Lighter, More Stable Battery
HFiPP increases the density of the Army’s batteries by 30% says research chemist Dr. Cynthia Lundgren (2). Dr. Lundgren is the chief of the Electrochemistry Branch of the Power and Energy Division in the Sensors and Electron Devices Directorate at ARL. Typical improvements to battery energy densities are in the 1% range, she says.
The battery-improvement substance has been known for five years now. As of September 2014, the Army had five pending patents related to the technology (3).
Research into battery improvements began when the Army decided it wanted a lighter battery for soldiers to carry on the battlefield, which will allow them to carry more of other things such as water and ammunition.
What the Army Uses Batteries For
Army soldiers use batteries for a number of equipment needs, on and off the battlefield. In fact, soldiers deployed to Afghanistan carried a minimum of 20 pounds of batteries for a three-day mission. These include batteries as small as AA to huge bricks that operate tactical radios. Some specialized equipment requires even bigger batteries, which forces some soldiers to carry a load of up to 35 pounds of batteries (4).
One soldier’s battery load may include batteries for the following personal and unit equipment:
–> Tactical radio
–> GPS receiver
–> MP3 player
–> Night vision goggles
–> Some weapons systems
–> And more
The more weight a soldier carries in combat the slower he moves and the less effective he is at executing his combat mission. That’s why the Army has prioritized improving its battery technology so that soldiers can perform better on the battlefield.
Extreme Conditions Require Extreme Power Storage
Soldiers often find themselves in extreme combat situations that sometimes includes extreme weather. Colder temperatures could be 50 degrees below zero. Warmer climates may reach into the 120s. Commercial batteries are typically not effective long-term at those temperatures (5).
Lithium-ion batteries need to be recharged. Currently, soldiers recharge their batteries most often by piggybacking off vehicle power. That leads to additional fuel consumption, which is another concern for military leaders.
Dr. Lundgren says getting beyond the 4.5V upper range for lithium-ion technology was a huge hurdle. The new batteries operate at 5V.
Other battery research taking place at ARL includes advanced battery chemistry in lithium-sulphur batteries, sodium batteries, dual-graphite batteries, and magnesium metal hybrid batteries.
Another area of research includes renewable energy for battery power. Dr. Lundgren says she wants to see military battery power become more like fuel cell power. An area of interest is metal air batteries, but there are ongoing challenges with that technology, she says.
The focus on improving rechargeable battery technology for the military came about as a result of challenges in the Iraq and Afghanistan theaters of war. Improvements in battery power could make the next war much more effective and lessen the load soldiers carry onto the battlefield.
References & Image Credits:
(1) Armed With Science
(2) U.S. Army Research Laboratory
(3) Military Smart Grids
(4) National Defense Magazine
(5) Army Technology
(6) Steven Duckworth via CC
(7) Lithium Ion Battery