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Design could enable longer lasting, more powerful lithium batteries

Tue, 04/20/2021 - 10:51 -- Paul Crompton

Researchers based at the US university Massachusetts Institute of Technology (MIT) have discovered a way to increase the energy density of lithium-ion batteries using a liquid solvent and salt electrolyte. 

The team’s electrolyte halts the unwanted chemical reactions that take place with the electrolyte that separates the metal electrodes.

Proffesor Jeremiah Johnson told BEST the electrolyte was made from two components: a liquid solvent and salt that is dissolved in the solvent. 

He said: “So far, we have made the solvent by combining dimethylamine and either triflic chloride or triflic anhydride. 

“Dimethylamine reacts with either of these to form a new nitrogen-sulfur bond that provides the final molecule. Once we have that, we add LiFSI salt (a commercially available salt) to it to form the final electrolyte.”

Researchers say the finding could make it possible for lithium-ion batteries to store about 420 Wh/kg, without sacrificing the cycle life.

The team say the carbon and fluorine electrolyte could be used as a “drop in” replacement for an existing electrolyte and would not require redesign of the entire battery system.

The research was published in the journal Nature Energy in a paper by MIT professors Ju Li, Yang Shao-Horn, and Jeremiah Johnson; postdoc Weijiang Xue; and 19 others at MIT. 

The research was supported by the U.S. Department of Energy and the National Science Foundation, and used facilities at Brookhaven National Laboratory and Argonne National Laboratory.

The electrolyte was initially developed by Shao-Horn, Johnson, and other research members, as part of an effort to develop lithium-air batteries. 

Shao-Horn, a professor of mechanical engineering and materials science and engineering, said: “The electrolyte is chemically resistant against oxidation of high-energy nickel-rich materials, preventing particle fracture and stabilising the positive electrode during cycling. 

“The electrolyte also enables stable and reversible stripping and plating of lithium metal, an important step toward enabling rechargeable lithium-metal batteries with energy two times that of the state-the-art lithium-ion batteries. 

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