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Liox Power reports first operation of a Li-air battery with a straight-chain alkyl amide electrolyte solvent; new direction for Li-air research

1 February 2013

Researchers at startup Liox Power, a California-based company developing rechargeable Li-air batteries, have demonstrated for the first time the operation of a lithium-air battery with a Li anode in a straight-chain alkyl amide electrolyte solvent (N,N-dimethylacetamide (DMA)/lithium nitrate (LiNO3)). A Li−O2 cell containing this electrolyte composition cycled for more than 2000 h (>80 cycles) at a current density of 0.1 mA/cm2, retaining >95% capacity and a consistent charging profile.

The discovery of an electrolyte system that is compatible with both electrodes in a Li−O2 cell may eliminate the need for protecting the anode with a ceramic membrane, and provides a new direction for Li−O2 battery research, the team suggests in their paper in the Journal of the American Chemical Society.

Lithium-air (Li-O2) batteries, with their superior energy density, are looked to as one of the possible “beyond Li-ion” solutions that could in the future accelerate the transition to full battery electric vehicles, among other applications. The DOE, in its recently released EV Everywhere Blueprint (earlier post) pegs lithium-air as one of the potential long-term (2017-2022) technologies required, but notes major challenges remain.

Demand for better electric vehicles motivates the search for lower cost, higher capacity, rechargeable batteries. Aprotic electrolyte Li−O2 batteries have received considerable attention due to very high theoretical specific energy, but degradation during cycling of every major component of the O2 electrode, including solvent, lithium salt, binder and carbon, has plagued efforts to develop this technology for practical purposes. Recognition that the most successful Li-ion battery materials are unsuitable for use in Li−O2 batteries has grown apace. In particular, solvents such as carbonates, ethers, esters, and lactones decompose in the presence of reactive oxygen species formed in the O2 electrode.

Recently, the superior stability of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) in the O2 electrode has been demonstrated by electrochemical mass spectrometry....The effective utilization of straight-chain alkyl amides as electrolyte solvents in Li−O2 batteries has heretofore been limited due to interfacial instability with Li anodes. The present study demonstrates the successful operation of a rechargeable Li−O2 battery using a Li metal anode and an electrolyte consisting of DMA and lithium nitrate (LiNO3).

—Walker et al.

Straight-chain alkyl amides are one of the few classes of polar, aprotic solvents that resist chemical degradation in the O2 electrode, the researchers note, but these solvents do not form a stable solid-electrolyte interphase (SEI) on the Li anode. Lack of a persistent SEI leads to rapid and sustained solvent decomposition in the presence of Li metal.

In their work, the Liox Power team used the salt, lithium nitrate (LiNO3) to stabilize the SEI.

In addition to demonstrating the 2000 h of cycling, the LioxPower team also found that O2 was the primary gaseous product formed during charging. This is important, they noted, because although other work has shown high cycle numbers in Li−O2 cells using carbonate- and ether-based electrolyte systems, these systems exhibited CO2 as the main gaseous product evolved during charging—indicating that electrolyte decomposition occurs rapidly in these cells.

The electrolyte composition described in this work demonstrates unprecedented stability toward both the O2 electrode and Li anode. The stability of this system can be attributed to the inertness of the amide core toward reactive oxygen species combined with the ability of the nitrate anion to contribute to the formation of a protective SEI that inhibits reaction between the solvent and the Li anode.

Heretofore it has been assumed that a ceramic membrane separating the anode and cathode compartments is required in order to enable the use of solvents that are unstable toward Li metal yet advantageous regarding the O2 electrode. The use of an SEI-forming Li salt instead of a ceramic membrane to prevent reactivity with the Li anode provides a new direction for Li−O2 battery research and creates opportunities in the identification of stable combinations of cell components.

—Walker et al.

Resources

  • Wesley Walker, Vincent Giordani, Jasim Uddin, Vyacheslav S. Bryantsev, Gregory V. Chase, and Dan Addison (2013) A Rechargeable Li-O2 Battery Using A Lithium Nitrate/N,N-Dimethylactamide Electrolyte. Journal of the American Chemical Society doi: 10.1021/ja311518s

February 1, 2013 in Batteries | Permalink | Comments (7) | TrackBack (0)

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Comments

Congratulations to Liox Power! Promising first step. The only reservation is the very very low current density. I don't know if they were being cautious or thats all they think they can get out of the battery w/o doing too much damage.

Post-Beyond Li-ion storage units with superior performance (5X) and lower cost (1/5) are essential for future extended range EVs. This technology (and others) may have the potential required?

Typically lithium air has very low current density because they get into a very diffusion limited regime with regard to the air delivery. Air is a very diffuse source of oxygen, and you just can't typically flow it fast enough through the porous electrode. Lithium air is not all that energy dense either. They say things like the cathode is way more energy dense, but they don't include the structure to hold the cathode material, the air passageway/delivery system or the air pump or any of the added gas handling portions of the cathode side which are not necessary for traditional chemistries. So, perhaps these things will be cheaper, but they will never be energy dense once you make the researchers make a fair comparison to the traditional lithium ion chemistries.

People should understand that it is very common for researchers to be very obtuse and obfuscatory regarding a specific technologies true viability because they need to get funding for their research. Having a PhD doesn't make you any more honest than anyone else.

These guys can prove me wrong by building one and reporting the energy density. Heck, someone please, tell me how this is wrong. Let's hear from the experts on li-air specifically how Li-air has a higher energy density. Just remember I will ask you to define the cathode and explain how you get the air in there and then show me what your current density is with your specific air delivery system. So, you can say "can" and "may" and not give details, but those only tell me where your problem is.

Very interesting new lead. May need to read the full article to understand why the authors mention explicitly straight chain alkyl amide, but only mention DMA (methyl groups are neither straigth nor branched imo). Current density appears pretty low, expect artificially kept low? Or would oxygen diffusion be the rate limiting step? Anyway, system appears to offer many opportunities for further chemical improvement. Would be interesting to learn how sensitive the system is to water for any practical application.

DMA and DMF seem as if they could be rather toxic.

I suppose the level to compare is battery - battery (including safety systems), rather than cathode - cathode.

Looks like Boeing have quite a problem on their hands.

Also, http://www.extremetech.com/computing/126745-ibm-creates-breathing-high-density-light-weight-lithium-air-battery

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