“Revolutionary” Advanced Battery Leaps Theoretical Maximum Boundary

April 26th, 2014 by Tina Casey

Just when you thought you knew everything about the theoretical maximum capacity of batteries, along comes the Oak Ridge National Laboratory to throw you for a loop. A team of researchers at ORNL has developed a pathway for “unprecedented energy density” in a battery that has already demonstrated a 26 percent increase over its theoretical maximum.

The ORNL team tested its concept on a lithium-carbon fluoride battery, which is considered “one of the best” batteries in the single-use (non-rechargeable) class for its high energy density.

Hold Your Breath On That Next-Gen EV Battery

Before we get into the nitty gritty, let’s pause and underscore that the finding involves single use batteries, so the implications for rechargeable EV batteries are remote at best.

However, according to ORNL the discovery could stretch single use battery life by “years or even decades.” That has significant implications for medical devices, remote sensors and keyless systems, and other applications where recharging is not an ideal solution.

In terms of our clean tech focus here at CleanTechnica, the improvement in lifecycle translates into significant resource conservation opportunities, including the potential for eliminating battery replacement surgery for medical devices.

Now think about how the medical device field is set to explode and you can see how a longer-lived battery comes into play.

For the record, ORNL isn’t the only federal agency interested in extending the life of lithium-carbon fluoride batteries. Army researchers are also on the case, pursuing a cathode-based track.

Secret Sauce for Next Generation Batteries

The beauty of the ONRL advanced battery discovery is that it involves a total rethinking of the role that each battery component plays.

For those of us who already forgot all the chemistry we learned in high school, here’s a quick review. Batteries consist of a cathode (positive charge), anode (negative charge), and an electrolyte, which conducts the ions (the charged particles).

Conventional battery engineering relies on the principle that each of the three components functions independently. In this system, the electrolyte is inactive in terms of maximizing battery capacity.

The ORNL team discovered that they could get the electrolyte and the cathode to interact in such a way that the electrolyte gains a capacity function to supplement the cathode.

They did that by incorporating a solid lithium thiophosphate (thiophosphate is a compound of phosphorus) electrolyte, which ORNL’s Chengdu Liang describes thusly:

As the battery discharges, it generates a lithium fluoride salt that further catalyzes the electrochemical activity of the electrolyte. This relationship converts the electrolyte — conventionally an inactive component in capacity — to an active one.

What’s All This About Lithium Thiophosphate?

If lithium thiophosphate doesn’t ring a bell, you’ll probably hear more about it soon. ORNL announced the development of a solid lithium thiophosphate electrolyte last year, the point being to replace the potentially flammable electrolyte in conventional lithium-ion batteries with a more stable electrolyte.

As for EV batteries, ORNL is running down a number of promising leads for next-generation technology including lithium-sulfur, possibly with the help of a new cathode developed by Pacific Northwest National Laboratory (the University of Arizona is also hot on the sulfur trail).

Sulfur is considered a good bet for its killer light weight – high density – low cost combo.

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