Go Army! US Army Researchers Develop New “Water Battery” For On-The-Go Energy Storage++
The US Army has been focusing on wearable electronics and advanced lithium-ion batteries to power the fighting force of the future, and they’ve come up with a new approach to energy storage that is tailor-made for your home electronics, too.
The challenge is to combine high performance with a super low risk of fire or explosion, and a research team from the Army Research Laboratory and the University of Maryland has reached a solution.
ARPA-E And The Energy Storage Ripple Effect
The energy storage field is super hot, and a lot of attention is focusing on battery packs for electric vehicles and stationary energy storage for buildings, grids and microgrids.
In comparison, the world of household electronics may not seem so exciting. However, since the new research is supported by ARPA-E, the Energy Department’s cutting-edge energy technology funding office, it’s probably a good bet that the chemistry behind the new battery research will have a transformative impact on the whole energy storage field.
Reducing Risk For Soldiers
The research team focused on rechargeable lithium-ion energy storage with a water-salt solution for an electrolyte. That type of battery provides sufficient voltage for laptops and other household electronics without the safety risks.
To be clear, safety systems are built into conventional lithium-ion batteries. The issue for soldiers on the go is that these systems add weight. Lighten the load and you get that much more back in endurance and force effectiveness.
In addition, although the risk of fire or explosion from properly designed Li-ion technology is minimal under normal conditions, the extreme conditions of Army activity — in training and in war zones — require that risk to be reduced even further.
Overcoming The “Cathodic Challenge”
Conventional aqueous batteries use electrodes based on a durable material, such as nickel, but the result is an energy storage solution with relatively low power.
The problem is how to boost power without sacrificing safety. The Army – UMD research team made some progress last year with a new aqueous battery reaching the 3.0 volt mark, but then they ran up against something called the cathodic challenge.
That’s what happens when a lithium or graphite electrode is degraded by contact with water in the electrolyte.
UMD’s Chongyin Yang developed a solution for the new, improved battery, in the form of a hydrophobic ceramic/polymer (aka plastic) gel coated onto the anode. That enables the use of lithium or graphite, which are much more efficient than nickel.
Here’s the explainer from the US Army:
This hydrophobic coating expels water molecules from the vicinity of the electrode surface and then, upon charging for the first time, decomposes and forms a stable interphase — a thin mixture of breakdown products that separates the solid anode from the liquid electrolyte. This interphase, inspired by a layer generated within non-aqueous batteries, protects the anode from debilitating side reactions.
Coming up with a formula for the new gel was a challenge all in itself. A balance had to be struck between effectively blocking contact with water, and allowing for a high level of performance.
With the new gel in hand, this year the researchers bumped performance up to the 4-volt level.