Energy

Lithium strips take next-gen battery into record-breaking territory

Lithium strips take next-gen b...
Scientists in the US have developed a novel lithium-metal battery that retains its functionality over 600 cycles
Scientists in the US have developed a novel lithium-metal battery that retains its functionality over 600 cycles
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Scientists in the US have developed a novel lithium-metal battery that retains its functionality over 600 cycles
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Scientists in the US have developed a novel lithium-metal battery that retains its functionality over 600 cycles
The left image shows electrolyte (blue) filling a pocket within a thin lithium anode, creating an effective SEI seen in green, compared to a thicker lithium anode with a largely ineffective SEI
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The left image shows electrolyte (blue) filling a pocket within a thin lithium anode, creating an effective SEI seen in green, compared to a thicker lithium anode with a largely ineffective SEI

One particularly promising architecture for next-generation batteries uses pure lithium-metal, a material with excellent energy density that could see electric vehicles travel many times farther on each charge. A research group in the US has taken a significant step forward with this technology, coming up with a design for a long-lasting lithium metal battery that remains functional for a record-breaking number of charging cycles.

The idea behind these types of batteries is to swap out the graphite used in the anode component for pure lithium metal, which can hold as much as 10 times the energy. Described as a dream material by some researchers, lithium metal is seen as key to helping us break through a key bottleneck in energy storage, but scientists have struggled with longevity issues with the versions developed so far failing quickly during use.

One of the reasons for that failure is the complex reactions that occur around the anode, affecting a thin film on top of it known as the solid electrolyte interphase (SEI). This film controls the molecules that enter the anode from the electrolyte solution, through which electrons travel back and forth to and from the battery's other electrode, known as the cathode.

In this way, this gatekeeping role tasks the SEI with the responsibility of preventing unwanted chemical reactions as the battery is cycled, and this is the mechanism targeted by the scientists from the U.S. Department of Energy’s Pacific Northwest National Laboratory (PNNL) in a new study. It is commonly thought that loading up the amount of lithium in the anode was one way to address this problem, but the team found success through another approach.

“Many people have thought that thicker lithium would enable the battery to cycle longer,” says Jie Xiao, a corresponding author of the paper. “But that is not always true. There is an optimized thickness for each lithium-metal battery depending on its cell energy and design.”

The scientists used very thin strips of lithium as the basis for their anode, each with a width of just 20 microns, far thinner than a human hair. This anode was worked into a pouch cell battery with an energy density of 350 Wh/kg. The best-in-class lithium-ion batteries in use today have a density of 250 to 300 Wh/kg, so while 350 Wh/kg isn't unheard of in research circles, it would be a marked improvement on currently available technologies.

The left image shows electrolyte (blue) filling a pocket within a thin lithium anode, creating an effective SEI seen in green, compared to a thicker lithium anode with a largely ineffective SEI
The left image shows electrolyte (blue) filling a pocket within a thin lithium anode, creating an effective SEI seen in green, compared to a thicker lithium anode with a largely ineffective SEI

In testing, the team found that the battery retained 76 percent of its capacity after a record 600 cycles. The same researchers had demonstrated an experimental lithium-battery that could operate across 50 cycles four years ago, then one capable of 200 cycles two years ago. This current record-setting version is another key step forward and, according to the team, lasts far longer than any others under development in similar research projects.

The team attributes the success of the design to the way the thinner strips facilitate a better SEI and therefore better interactions between the electrolyte and anode, compared to thicker strips that smother important electrochemical reactions. Having solved a key issue relating to lithium metal batteries, the authors are hoping to continue to improve the technology through a multi-institute consortium known as Battery500, which is working towards an energy density of 500 Wh/kg.

“The Battery500 Consortium has made great progress in increasing the energy density and extending the cycle life,” says Stanley Whittingham, 2019 Nobel Prize laureate in chemistry and a coauthor of the paper. “But much more needs to be done. In particular, there are safety issues with lithium-metal batteries that must be addressed. That’s something that the Battery500 team is working hard to resolve.”

The research was published in the journal Nature Energy.

Source: Pacific Northwest National Laboratory

16 comments
16 comments
dan
500 W/kg in the future? Good. In comparison to fuel (ca. 12'000 W/kg), these future batteries will be 4 % as powerful in the future as fuel is today... So, for 1 kg of fuel, you'd still need 25 kg of these future batteries. Hoping for better efficiency of electrical systems, it maybe 15 or 10 kg... So this very bad weight factor of ten or twenty is and will be a huge challenge. Please do further research!!!
paul314

So if I have a 300-mile battery pack, 600 charge cycles would be somewhere upward of 150,000 miles. Seems plausible.
Catweazle
Indeed dan.
Further, when you take into account that unlike a battery, fuel load is decreasing in mass between full and as the fuel is used up, you can effectively double that weight factor disadvantage.
dan
@catweazle. Sure, you are right. In particular for commercial aircrafts. But we never should underestimate potential of anybody or any technology. but if scientists celebrate a battery of 4 % of the power to existing technology/fuel (that even is favourouble for a lower landing weight) we are very far away from any eVtOL application or fully substitution as it is not competitive with fuel. And by the way, I even have read about 500 W/kg some years ago, on this blog, when this site still had the old name...
BlueOak
@Dan & @Weazle, technically true, but you’re evaluating the two “fuels” too narrowly.

Batteries don’t have to reach anywhere near the energy density of ICE fuels to be successful.

Once the fuel in an ICE vehicle is used up, the supply chain must replenish it. Whereas, with a battery, energy in the form of electricity is far more efficiently “transported” to the “refueling” location. Unlike ICE fuel, that refueling location can easily be the owners home or workplace. Furthermore, electricity can be “manufactured” anywhere by anyone using solar or wind, completely eliminating the need to transport it.

So the real measure of success for EV’s will be when they reach distance and purchase price parity with ICE vehicles. Already EVs have dramatically lower maintenance and “fuel” costs vs ICE vehicles.
Kpar
So they want to use Lithium metal, huh? I wonder how the various fire departments will react to a vehicle fire. Spray water on a Lithium fire and watch what happens!
Signguy
We need a better source; Lithium is a rare element coming mostly from China, so it's limited in more ways than one.
There are all kinds of new battery technologies coming out that need our attention.
Adrian Akau
Cars need to be made lighter and with a lower coefficient of air resistance to take better advantage of the batteries.
Eddy
Currently a plane that requires to land again shortly after take-off has to circle for ages to burn off fuel or dump it in order to get down to a safe landing weight and speed.
Can't jettison those expensive heavy batteries.
Simon M
@Dan and @Catweazle you’re right, though outside of the field of transportation/electric vehicles there are battery uses where ICE are less practical.

As for lithium fires, industrial availability and recycling, there are lots of research projects addressing these issues and many seem promising, especially if your standards are not based around electrical vehicles.
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