Science

All-solid lithium-sulfur battery stores four times the energy of lithium-ions

All-solid lithium-sulfur batte...
Researchers are building an all-solid Li-S battery that is cheap, safe, durable, and stores four times the charge of conventional lithium-ion batteries (Photo: ORNL)
Researchers are building an all-solid Li-S battery that is cheap, safe, durable, and stores four times the charge of conventional lithium-ion batteries (Photo: ORNL)
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The new Li-S battery design overcomes the problems with previous attempts (Photo: ORNL)
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The new Li-S battery design overcomes the problems with previous attempts (Photo: ORNL)
Researchers are building an all-solid Li-S battery that is cheap, safe, durable, and stores four times the charge of conventional lithium-ion batteries (Photo: ORNL)
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Researchers are building an all-solid Li-S battery that is cheap, safe, durable, and stores four times the charge of conventional lithium-ion batteries (Photo: ORNL)

Researchers at the Oak Ridge National Laboratory (ORNL) have come up with a promising design for a lithium-sulfur rechargeable battery that is considerably cheaper and more energy-dense than standard lithium-ions. Using a solid electrolyte rather than a liquid one, the battery is also testing much safer and more durable than previous designs.

Lithium-sulfur batteries are seen by some as the successors of lithium-ions because they are extremely light (they are often used for solar-powered flight), they can reach an impressive energy density, and they are cheaper to produce.

But the technology isn't quite mature yet, and as it turns out, the two major limitations with Li-S batteries have to do with the electrolyte. An electrolyte is a substance that, when mixed with a solvent, releases ions, making it electrically conductive. In batteries, electrolytes transport charge between the two electrodes, converting chemical energy into electrical energy.

In previous Li-S battery designs, the electrolyte used was liquid in nature. This proved a double-edged sword: the liquid electrolyte is an excellent conductor because of how it dissolves the lithium compounds, but this dissolution also causes the battery to break down prematurely. The liquid electrolyte is also flammable, posing serious safety concerns.

But now, researchers may have found a way around these problems.

"Our technology overcomes the capacity fade and safety issues of Li-S technology," Dr. Chengdu Liang, lead author of a paper on the research, told Gizmag. "The battery still performs well after a few hundred cycles, and the volumetric density could be slightly better than Li-ion batteries."

The new Li-S battery design overcomes the problems with previous attempts (Photo: ORNL)
The new Li-S battery design overcomes the problems with previous attempts (Photo: ORNL)

The researchers overcame these barriers by building a solid electrolyte made of lithium polysulfidophosphates (a new class of sulfur-rich materials with good electrical conductivity) to create an energy-dense, all-solid battery that is showing a lot of promise.

Even after 300 charge-discharge cycles at 60°C (140ºF), the battery retained a capacity of 1200 mAh/g (milliampere-hours per gram), compared to the 140-170 mAh/g of a traditional lithium-ion battery (lithium-sulfur batteries, however, only deliver about half the voltage of lithium-ions, so this 8-fold increase actually translates into a 4-fold increase in energy density).

The battery uses elemental sulfur, which is a byproduct of industrial petroleum processing. In other words, the battery could also provide a way to recycle industrial waste into a useful – perhaps even superior – technology.

"The main limitation is the relatively low ionic conductivity of the solid electrolyte," said Liang. "So the power density is lower than Li-ion batteries, but it can be improved with a better solid electrolyte. Moreover, the ceramic structure is brittle, and much optimization is needed."

The technology is still in the early stages of development, but Liang and colleagues are working on ironing out these issue and have filed a patent application for their battery design.

The paper detailing the study was recently published in the journal Angewandte Chemie.

Update 06.10.13: Gizmag wrote back to Dr. Chengdu Liang for more details of the battery's charging and discharging behavior. Here is his response:

"We did not observe self-discharge. A charged cell was put on shelf for over a week, and it still delivered the same capacity. The essence of our all-solid battery design is to eliminate the self-discharge through the all-solid configuration.

"This battery charges slower than Li-ion battery at the current status for a simple reason; the ionic conductivity of both the solid electrolyte and cathode are not high energy to have high current density. Much better performance at elevated temperatures such as 60 degrees C or higher."

Source: ORNL

17 comments
asdf
This sounds really good. So.. whats the catch? xD If this becomes a reallity just imagine..
JimRD
It means I can fly my rc planes 20+ minutes instead of 10 mins/charge. That's a good thing.
Fredrik Haugen
My Quadrocopter will go from 7 minutes to 28mins =) Sweet!
Slowburn
What is its self discharge rate? How long does it take to charge?
Incra Mant
If there is to be a last longer battery, the gadget constructors will also make more powerful gadgets, (phones, tablets, laptops etc) and thus making them more power hungry. We will still struggle with 6 hours phones on a single charge.
Craig Jennings
It must be coming the replacement for the LI-ON. With 70 odd million tonnes of Sulphur being produced a year this would be a handy use for it, if only Lithium poured out of petroleum as well! Also ^ Slowburns question + 1
myale
Quite surprised carbon nanotubes did not pop up in this article - curious to know if they looked at nanotube networks coated with the lithium sulphur technology. Guess this may of put it into the box where it looks great but have we actually seen any of it come to fruition.
martinkopplow
Well, if I understand the article right, the bottleneck is the max. current that can be drawn out of these. Offering a higher capacity, they seem suited to applications that do not drain them too fast, so it's probably not R/C planes, as these are notorious for high discharge rates.
Instead, my electric car could run a lot longer with tech like this, as cars do discharge at a relatively low rate, surprisingly, for many. For comparison: An R/C plane drains a battery in minutes, an electric car in hours. I'll follow this.
Foiled
Slowburn's question +2 now
jumpjack
An electric car with such a battery would have a 300 miles range and would hopefully cost 20000$ rather than 40000$.
Anyway, about current drain, I know e-scooter drain 40-80 Ampere (for 2000-5000W range, 48-72V range). Don't know about cars.