Game-changing! Two-dimensional materials help lithium-air batteries bring breakthroughs

Lithium-air batteries are expected to be the next revolutionary replacement for the lithium-ion batteries currently used in electric cars, cell phones and computers.

Lithium-air batteries, which are still in the experimental stages of development, can store 10 times more energy than regular lithium-ion batteries and are also much lighter. That said, they could be even more efficient and more rechargeable if advanced catalysts made from two-dimensional materials (materials where electrons can move freely [in planes] only in two dimensions, not on a nanometer scale [1-100nm]) were used. Catalysts help increase the rate of chemical reactions inside a battery, and depending on the type of material used as a catalyst, they can significantly improve a battery's ability to hold and deliver energy.

"We're going to need very high energy density to power new technologies like cell phones, laptops and especially electric cars," said Amin Salehi-Khojin, associate professor of mechanical and industrial engineering in UICs College of Engineering. Salehi-Khojin and his colleagues synthesized several two-dimensional materials that can act as catalysts. They found that some of the two-dimensional materials, when added as catalysts to experimental lithium-air batteries, enabled the batteries to pack 10 times more energy than lithium-air batteries containing traditional catalysts. Their findings were published in the journal Advanced Materials.

Salehi-Khojin, the corresponding author of the paper, said: "Currently, electric vehicles travel an average of about 100 miles per charge, but if we add two-dimensional material catalysts to lithium-air batteries, we can get closer to 400 to 500 miles per charge, which will be a real game changer. This will be a huge breakthrough in energy storage."

Salehi-Khojin and his colleagues synthesized 15 different types of two-dimensional transition metal dichalcogenides. TMDCs are unique compounds because they have high electronic conductivity and fast electron transfer, which can be used to participate in reactions with other materials, such as those that occur inside batteries during charging and discharging.

The researchers experimented with the performance of 15 TMDCs as catalysts in an electrochemical system that mimics a lithium-air battery.

Leily Majidi, a graduate student in the UIC College of Engineering and the paper's first author, explained that in a 2D structure, TMDCs have better electronic properties and a larger reactive surface area, allowing them to participate in electrochemical reactions within the battery while maintaining a stable structure.

These materials react much faster than traditional catalysts such as gold or platinum, Majidi said.

One of the reasons 2D TMDCs work so well is that they help speed up the charge and discharge reactions in lithium-air batteries.

This is known as the catalyst's bifunctionality, Salehi-Khojin said.

2D materials also work in tandem with electrolytes, which are materials through which ions pass during the charging and discharging process.

The 2D TDMCs and ionic liquid electrolyte we used act as a co-catalyst system to help electrons transfer faster, leading to faster charge transfer and more efficient storage and release of energy.

“These new materials represent a novel pathway to take batteries to the next level,” Salehi-Khojin said. “We just need to find ways to produce and tune the batteries more efficiently on a larger scale.”

Poya Yasaei, Zahra Hemmat, Pedram Abbasi, Shadi Fuladi, Xuan Hu, Robert Klie, Fatemeh Khalili-Araghi and Baharak Sayahpour of the University of Illinois at Chicago and Robert Warburton and Jeffrey Greeley of Purdue University are co-authors of the paper.

This research was supported in part by National Science Foundation DMREF Grant 1729420.

(Original text from: Daily Science New Energy Network Comprehensive)