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New breakthrough in lithium-ion batteries could double energy density



Researchers have developed a new way to construct lithium-ion batteries that could pave the way for greater energy densities, performance and battery safety, according to a Penn State report.

The solid electrolyte interphase

Between the lithium metal of the battery and its electrolytes is the solid electrolyte interphase (SEI) and has for years been an obstacle to the development of more powerful batteries.

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Rechargeable lithium-ion batteries are in increasing demand for higher energy densities, as they are used in all types of electronic devices, from mobile phones to electric vehicles. Therefore, the SEI is of course one of the stations where researchers are trying to improve performance.

"This layer is very important and is naturally formed by the reaction between the lithium and the electrolyte in the battery," said Donghai Wang, a professor of mechanical and chemical engineering at Penn State University. "It does not behave very well, which causes many problems."

Creating a Better Solid-State Electrolyte Interphase

The problems begin when the SEI begins to degrade. Over time, dendrites, needle-like growths on the lithium electrode of the battery, gradually deteriorate their performance and safety.

"That's why lithium-metal batteries stop longer ̵

1; the interphase grows and grows, it's not stable," said Wang. "In this project, we used a polymer composite to create a much better SEI."

Under the leadership of Yue Gao, a chemistry graduate student at Penn State, engineers developed a new SEI, a reactive polymer composite consisting of polymeric lithium salt, lithium fluoride nanoparticles, and graphene oxide plates.

Thomas E. Mallouk, Professor of Chemistry at Evan Pugh University, supported the project in producing the thin layers of materials.

"It takes a lot of molecular-level control to achieve a stable lithium interface," Mallouk said. "The polymer developed by Yue and Donghai reacts to form a claw-like bond to the lithium metal surface, passively giving the lithium surface what it wants, so that it does not react with the molecules in the electrolyte, acting as a nanosheet in the composite as a mechanical barrier to prevent the formation of dendrites from lithium metal. "

This was achieved by controlling the surface of lithium at the level of single atoms and molecules, which enabled the project to be successful. [19659014] "When we develop batteries, we do not necessarily think like chemists, down to the molecular level, but that's what we had to do here," Mallouk said.

"With a more stable SEI, it is possible to double the energy density of today's batteries while keeping them longer lasting and safer," Wang said.

The research was published today in the journal Nature Materials .


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