Boston College researchers have applied a ‘water-in-salt’ electrolyte that enables stable operation of a lithium-air battery, offers superior long cycle lifetimes and presents a platform that could help lithium-ion batteries achieve their full potential.

This news finally comes after more than two decades of research where improvements to lithium-ion batteries have stalled short of their theoretical potential. As an electrochemical energy storage technology, upgrading performance requires improved stability of electrolytes. Harnessing the full electrochemical power of lithium-oxygen batteries requires an efficient, more stable electrolyte.

The team found a way around the problem of instability that arises from the use of water in the development of aqueous electrolytes.

Image Credit: Boston College. Click Image for the largest view.

In an effort to find a suitable electrolyte system, the team’s water-in-salt approach involves no organic solvents. It consists of super-concentrated lithium salt, known as LiTFSI, in which water molecules lock onto the ions and experience less degradation when in contact with oxygen molecules, according to the researchers, led by Boston College Professor of Chemistry Dunwei Wang.

Wang said, “We employed an unorthodox approach of using a water-based electrolyte for Li-O2 batteries. Previously, water was thought to be extremely bad for Li-O2 battery operations because it would promote parasitic chemical reactions to significantly undermine the desired chemistry. We discovered that when the salt concentration is high, most water molecules can be locked down so that they provide the right functionalities such as conductivity but exhibit little of the parasitic chemical reactions.”

The result is a “highly effective electrolyte that permits stable Li-O2 battery operations on the cathode with superior cycle lifetimes,” the team reported in the journal Chem with the article titled “Cathodically Stable Li-O2 Battery Operations Using Water-In-Salt Electrolyte.” Experiments showed the electrolyte enables stable lithium-air battery operations up to 300 cycles, making it competitive for practical applications.

The team sought to overcome the limitations that have plagued earlier efforts to tame the complex chemical reactions within lithium-air battery prototypes, said Wang, who conducted the project with Boston College researchers Qi Dong, Xiahui Yao, Yanyan Zhao, Miao Qi, Xizi Zhang and Yumin He, and Hongyu Sun from the Technical University of Denmark.

“We studied a new concept for Li-O2 batteries,” said Wang. “We used a combination of electrochemistry and materials characterization tools to carry out the study. Our goal is to enable stable, high-performance Li-O2 battery operations.”

Wang said the researchers will next try to build upon the results for practical fuel cell applications and also work to reduce the cost of producing the electrolyte.

Lithium air technology has immense potential along with implied safety. Perhaps this lab specimen is a breakthrough. More research and testing is in order to illuminate the path to scaling up. Lets hope the progress is rapid, the cycle lifetime improves, and the result is low cost.


1 Comment so far

  1. Jagdish on April 23, 2018 12:04 PM

    Lithium is going to be a short supply item. Further research on magnesium could be fruitful.

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