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2D niobium and vanadium carbides as promising materials for high-power Li-ion batteries; extending MXenes

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Specific lithiation (circles.) and delithiation (squares) capacities (per mass of active material) vs cycle number at different rates for Nb2CTx and V2CTx-based electrodes compared to previously reported Ti2C. Credit: ACS, Naguib et al. Click to enlarge.

Researchers at Drexel University report in a paper in the Journal of the American Chemical Society on the potential for 2D niobium and titanium carbide materials as high-power electrode materials for Li-ion batteries (LIBs). Earlier this year in a paper in Science, the team had reported on the high volumetric capacitance and intercalation of other “MXene” structures. (Earlier post.)

Testing of the two new MXenes—Nb2CTx and V2CTx—as electrodes materials in LIBs showed that each has its own voltage profile. Nb2CTx showed good reversible capacity (170 mAh·g-1 at 1C) at lower lithiation voltages; V2CTx showed higher capacities (210 mAh·g−1 and 260 mAh·g−1) at higher lithiation voltages. Both Nb2CTx and V2CTx showed excellent capability to handle high cycling rates (10C), suggesting fast Li diffusion between MXene layers and potential use in high power applications, the team found.

Dr. Michel W. Barsoum and Dr. Yury Gogotsi, professors in Drexel’s College of Engineering, discovered several years ago that atomically thin, two-dimensional materials—similar to graphene—that have good electrical conductivity and a surface that is hydrophilic, or can hold liquids. They named these new materials “MXenes,” which hearkens to their genesis through the process of etching and exfoliating atomically thin layers of aluminum from layered carbide “MAX phases.” (The latter also discovered at Drexel about 15 years ago by Barsoum.)

Recently, our discovery of 2D early transition metal carbides and carbonitrides that we labeled MXenes further extended the family of 2D inorganic materials to include: Ti3C2, Ti2C, Ta4C3, (Ti0.5,Nb0.5)2C, (V0.5,Cr0.5)3C2, and Ti3CN...Potential applications for MXenes range from conductive reinforcement fillers for polymers, to catalysts and sensors, transparent conductors, and many others. Of special interest to this work is the use of MXenes as electrode materials in electrical energy storage such as supercapacitors, lithium ion batteries (LIBs), and lithium-ion capacitors.

The lithiation and delithiation mechanisms were found to be Li intercalation and deintercalation between the MXene layers. In general, MXenes with n = 1, viz., M2X ...should have higher gravimetric capacities compared to their higher order counterparts such as M3X2 or M4X3, because the former have less atomic layers compared to the latter (3 atomic layers vs 5 and 7, respectively). Furthermore, M2X-based MXenes should possess higher specific surface areas as compared to their higher order counterparts. Herein we report, for the first time, on the synthesis of two new 2D phases, Nb2CTx and V2CTx, and their Li uptake and cyclability at high rates.

—Naguib et al.

In the analysis of the electrochemical testing results, the team noted that although the reversible capacity of MXenes at high cycling rates (i.e., 10 C) is comparable to titania-based anodes, the latter have maximum theoretical capacities of the order of 170 mAh·g−1 even at slow scan rates, while V2CTx displayed a reversible capacity of up to 260 mAh·g−1 at 1 C.

Further, the results were obtained on just synthesized and not well-purified compounds; refinement could deliver some upside.

The higher rate performances, however, are encouraging and suggest that Nb2CTx and V2CTx can be used as promising electrode materials in LIBs, especially for high power applications. For example, the Li-capacities of additives-free fully delaminated Ti3C2Tx electrodes were roughly 4 times those of non-delaminated Ti3C2Tx.

—Naguib et al.

Resources

  • Michael Naguib, Joseph Halim, Jun Lu, Kevin M. Cook, Lars Hultman, Yury Gogotsi, and Michel W. Barsoum (2013) “New Two-Dimensional Niobium and Vanadium Carbides as Promising Materials for Li-Ion Batteries”, Journal of the American Chemical Society doi: 10.1021/ja405735d

Comments

HarveyD

This could become one more of the 1001 ways to make higher performance batteries. Which ones will be mass produced at and affordable price?

Arnold

For some years there has been reporting of mineral analysis of plat material using (in this case) the Melbourne synchrotron.

The discovery of high ore concentrations led to speculation that mining the concentrated ore may be feasible. More recent reports show Eucalyptus spp can accumulate gold from ~ as much as 30M above the ore boy and so indicate the presence of.

The Svern synchrotron ( collider ) can (has) look into meteoric rock to see atomic sized structure without damage. The objective to find crevices that could be suitable for bacterial habitat ( extraterrestrial life).

This is the same principle, Xray tomography, as used to look inside of this battery :

http://www.greencarcongress.com/2013/10/20131018-ebner.html

It is such a powerful tool for non destructive observation in that it can prove theoretical physics (chemistry) in real time dynamic testing.
Probably expensive to run so the industrial application would be limited to very high potential technologies.

Battery testing should qualify owing to the extremely high economic and environmental payoffs.Bringing theoretical potentials closer to realisation.

If this goes as expected, it'll be time 'fasten your seatbelts'


danschl

niobium is rarer than lithium
to make it afforable need a more abundant element

Brotherkenny4

As the base metals, how do Nb and V compare to say Co, Ni, Fe or Mn on a cost basis? Certainly, a higher energy density can offset increased base material costs, but these number don't appear so high that the material costs can be ignored. Danschl, lithium is not rare or costly or limited in supply or even a large cost within the lithium ion battery. It is less than 2% of the cost. Seek out professional journals and read the articles on lithium.

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