New discovery makes fast-charging, better performing lithium-ion batteries possible


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April –  2019 – Rensselaer Polytechnic Institute – Material Science

Creating a lithium-ion battery that can charge in a matter of minutes but still operate at a high capacity is possible, according to research from Rensselaer Polytechnic Institute just published in Nature Communications. This development has the potential to improve battery performance for consumer electronics, solar grid storage, and electric vehicles.

A lithium-ion battery charges and discharges as lithium ions move between two electrodes, called an anode and a cathode. In a traditional lithium-ion battery, the anode is made of graphite, while the cathode is composed of lithium cobalt oxide.

These materials perform well together, which is why lithium-ion batteries have become increasingly popular, but researchers at Rensselaer believe the function can be enhanced further.

“The way to make batteries better is to improve the materials used for the electrodes,” said Nikhil Koratkar, professor of mechanical, aerospace, and nuclear engineering at Rensselaer, and corresponding author of the paper. “What we are trying to do is make lithium-ion technology even better in performance.”

Vanadium Sulfide download

Vanadium disulfide – a promising new monolayer material for Li-ion batteries

Koratkar’s extensive research into nanotechnology and energy storage has placed him among the most highly cited researchers in the world. In this most recent work, Koratkar and his team improved performance by substituting cobalt oxide with vanadium disulfide (VS2).

“It gives you higher energy density, because it’s light. And it gives you faster charging capability, because it’s highly conductive. From those points of view, we were attracted to this material,” said Koratkar, who is also a professor in the Department of Materials Science and Engineering.

Excitement surrounding the potential of VS2 has been growing in recent years, but until now, Koratkar said, researchers had been challenged by its instability–a characteristic that would lead to short battery life. The Rensselaer researchers not only established why that instability was happening, but also developed a way to combat it.

The team, which also included Vincent Meunier, head of the Department of Physics, Applied Physics, and Astronomy, and others, determined that lithium insertion caused an asymmetry in the spacing between vanadium atoms, known as Peierls distortion, which was responsible for the breakup of the VS2 flakes. They discovered that covering the flakes with a nanolayered coating of titanium disulfide (TiS2)–a material that does not Peierls distort–would stabilize the VS2 flakes and improve their performance within the battery.

“This was new. People hadn’t realized this was the underlying cause,” Koratkar said. “The TiS2 coating acts as a buffer layer. It holds the VS2 material together, providing mechanical support.”

Once that problem was solved, the team found that the VS2-TiS2 electrodes could operate at a high specific capacity, or store a lot of charge per unit mass. Koratkar said that vanadium and sulfur’s small size and weight allow them to deliver a high capacity and energy density. Their small size would also contribute to a compact battery.

When charging was done more quickly, Koratkar said, the capacity didn’t dip as significantly as it often does with other electrodes. The electrodes were able to maintain a reasonable capacity because, unlike cobalt oxide, the VS2-TiS2 material is electrically conductive.

Koratkar sees multiple applications for this discovery in improving car batteries, power for portable electronics, and solar energy storage where high capacity is important, but increased charging speed would also be attractive.

Rensselaer college-photo_3861

Rensselaer Polytechnic Institute

 

Vanadium disulfide flakes with nanolayered titanium disulfide coating as cathode materials in lithium-ion batteries Lu Li, Zhaodong Li, Anthony Yoshimura, Congli Sun, Tianmeng Wang, Yanwen Chen, Zhizhong Chen, Aaron Littlejohn, Yu Xiang, Prateek Hundekar, Stephen F. Bartolucci, Jian Shi, Su-Fei Shi, Vincent Meunier, Gwo-Ching Wang & Nikhil Koratkar Nature Communications volume 10, Article number: 1764 (2019)

Rensselaer Polytechnic Institute

#Batteries #Energy #MaterialScience

Electrodes Push Charging Rate Limits in Energy Storage: Using MXene in Electrode Design: Drexel University


Drexel Energy Storage Electrodes Key rd1707_MXene-electrode-crop

Drexel researchers developed electrode designs using MXene that allow for much faster charging because they open up paths for ions to quickly travel within the material. Source: Drexel University

 

Can you imagine fully charging your cell phone in just a few seconds? Researchers in Drexel University’s College of Engineering can, and they took a big step toward making it a reality with their recent work unveiling of a new battery electrode design in the journal Nature Energy.

The team, led by Yury Gogotsi, PhD,Distinguished University and Bach professor in Drexel’s College of Engineering, in the Department of Materials Science and Engineering, created the new electrode designs from a highly conductive, two-dimensional material called MXene. Their design could make energy storage devices like batteries, viewed as the plodding tanker truck of energy storage technology, just as fast as the speedy supercapacitors that are used to provide energy in a pinch — often as a battery back-up or to provide quick bursts of energy for things like camera flashes.

“This paper refutes the widely accepted dogma that chemical charge storage, used in batteries and pseudocapacitors, is always much slower than physical storage used in electrical double-layer capacitors, also known as supercapacitors,” Gogotsi said. “We demonstrate charging of thin MXene electrodes in tens of milliseconds. This is enabled by very high electronic conductivity of MXene. This paves the way to development of ultrafast energy storage devices than can be charged and discharged within seconds, but store much more energy than conventional supercapacitors.”

The key to faster charging energy storage devices is in the electrode design. Electrodes are essential components of batteries, through which energy is stored during charging and from which it is disbursed to power electronic devices. So the ideal design for these components would be one that allows them to be quickly charged and store more energy.

To store more energy, the materials should have places to put it. Electrode materials in batteries offer ports for charge to be stored. In electrochemistry, these ports, called “redox active sites” are the places that hold an electrical charge when each ion is delivered. So if the electrode material has more ports, it can store more energy — which equates to a battery with more “juice.”

Collaborators Patrice Simon, PhD, and Zifeng Lin, from Université Paul Sabatier in France, produced a hydrogel electrode design with more redox active sites, which allows it to store as much charge for its volume as a battery. This measure of capacity, termed “volumetric performance,” is an important metric for judging the utility of any energy storage device.

To make those plentiful hydrogel electrode ports even more attractive to ion traffic, the Drexel-led team, including researchers Maria Lukatskaya, PhD, Sankalp Kota, a graduate student in Drexel’s MAX/MXene Research Group led by Michel Barsoum, PhD,distinguished professor in the College of Engineering; and Mengquiang Zhao, PhD, designed electrode architectures with open macroporosity — many small openings — to make each redox active sites in the MXene material readily accessible to ions.

Mxene 2 containingou“In traditional batteries and supercapacitors, ions have a tortuous path toward charge storage ports, which not only slows down everything, but it also creates a situation where very few ions actually reach their destination at fast charging rates,” said Lukatskayathe first author on the paper, who conducted the research as part of the A.J. Drexel Nanomaterials Institute. “The ideal electrode architecture would be something like ions moving to the ports via multi-lane, high-speed ‘highways,’ instead of taking single-lane roads. Our macroporous electrode design achieves this goal, which allows for rapid charging — on the order of a few seconds or less.”

The overarching benefit of using MXene as the material for the electrode design is its conductivity. Materials that allow for rapid flow of an electrical current, like aluminum and copper, are often used in electric cables. MXenes are  conductive, just like metals, so not only do ions have a wide-open path to a number of storage ports, but they can also move very quickly to meet electrons there. Mikhael Levi, PhD, and Netanel Shpigel, research collaborators from Bar-Ilan University in Israel, helped the Drexel group maximize the number of the ports accessible to ions in MXene electrodes.mxene-polymer-nanocomposite-material

Use in battery electrodes is just the latest in a series of developments with the MXene material that was discovered by researchers in Drexel’s Department of Materials Science and Engineering in 2011. Since then, researchers have been testing them in a variety of applications from energy storage to electromagnetic radiation shielding, and water filtering. This latest development is significant in particular because it addresses one of the primary problems hindering the expansion of the electric vehicle market and that has been lurking on the horizon for mobile devices.

“If we start using low-dimensional and electronically conducting materials as battery electrodes, we can make batteries working much, much faster than today,” Gogotsi said. “Eventually, appreciation of this fact will lead us to car, laptop and cell-phone batteries capable of charging at much higher rates — seconds or minutes rather than hours.”

This research was supported by Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy’s Office of Science and Office of Basic Energy Sciences; as well as the National Science Foundation and Binational Science Foundation, which supported collaborations with France and Israel, respectively.

What are MXenes ?

MXenes are a new family of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides that were discovered and developed in collaboration with Prof. Barsoum’s group, that can be used in many applications. These applications include lithium-ion and sodium-ion energy storage systems, electromagnetic interference (EMI) shielding, and water purification. MXenes are highly desirable in EMI shielding due to their good flexibility, easy processing, and high conductivity with minimal thickness, having the highest EMI shielding effectiveness of all synthetic materials of similar thickness. MXenes are also promising antibacterial agents, with higher efficiency than graphene oxide in diminishing bacterial cell viability.

 

 

AE_Nanomaterials_Figure 1Read More: 2D Carbides and Nitrides (MXenes)