New technology aims to improve the life of lithium metal batteries and safety

According to Penn State researchers, rechargeable lithium metal batteries with increased energy density, increased performance and safety are possible with a newly developed solid electrolyte interphase (SEI).

As the demand for higher energy density lithium metal batteries increases – for electric vehicles, smartphones and drones – the stability of the UTE has been a critical problem to prevent advancement as a layer of salt on the surface of the lithium electrode of the battery conducts lithium ions.

"This layer is very important and is naturally formed by the reaction between lithium and the electrolyte in the battery," said Donghai Wang, a professor of mechanical and chemical engineering. "But it does not behave very well, which causes a lot of problems."

The degradation of the SEI, one of the least understood components of lithium metal batteries, contributes to the development of dendrites, needle-like formations that develop from the lithium electrode of the battery and harm the performance and security. The researchers published their approach to this problem today (March 11) in Nature Materials.

"That's why lithium metal batteries do not last longer: the interphase is growing and it's not stable," said Wang. "In this project, we used a polymer composite to create a much better SEI."

Under the supervision of Yue Gao, PhD student in chemistry, the enhanced SEI is a reactive polymer composite consisting of lithium polymer salt, lithium fluoride nanoparticles and graphene oxide sheets. The original construction of this drum component has thin layers of materials, to which Thomas E. Mallouk, professor of chemistry at Evan Pugh University, has contributed his expertise.

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

Thanks to both chemistry and engineering design, the collaboration between the fields has enabled the technology to control the lithium surface at the atomic scale.

"When we build batteries, we do not necessarily think like chemists, up to the molecular level, but that's what we have to do here," Mallouk said.

The reactive polymer also reduces the weight and cost of manufacturing, further improving the future of lithium metal batteries.

"With a more stable SEI, it is possible to double the energy density of current batteries, while making them more durable and safer," said Wang.

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More information:
Interphase polymer – inorganic solid – electrolyte for lithium metal batteries stable in lean electrolyte conditions, Nature Materials (2019). DOI: 10.1038 / s41563-019-0305-8, https://www.nature.com/articles/s41563-019-0305-8