Breakthrough in solid electrolyte interface components of lithium batteries

Although lithium-ion batteries are the mainstream of energy storage today, the molecular and atomic basic science of charge and discharge is still a mystery.

According to the study of the Department of Energy Argonne National Laboratory in NatureCatalysis, the research team has achieved a breakthrough in the chemical composition of the solid electrolyte interface(solid-electron electrolyte, SEI) between the electrode and the liquid electrolyte. This will help improve the team's ability to predict battery life, which is critical for electric-vehicle manufacturers, said Dusan Strmcnik, chemical engineer at the Argonne National Laboratory's Materials Science Department(MSD).

Scientists have long been committed to cracking the lithium ion battery SEI, but only know that the formation of the battery will form SEI when it is recharged, and a one-thousand-thousand-million-millimetre thick film will be produced on the graphite electrode, and the film can protect the interface from harmful reactions. At the same time, lithium ions shuttle between electrodes and electrolytes, so for lithium ion batteries, a well-performing SEI is a necessary condition. Strmcnik pointed out that battery efficiency and life depends on SEI quality. If scientists can find out its chemical properties and independent composition rules, they can improve battery efficiency through SEI.

Therefore, the Argonne National Laboratory formed an international research team with the University of Copenhagen, Denmark, the Technical University of Munich, Germany, and the BMW Group, and successfully solved lithium fluoride, a common chemical substance of lithium ion battery SEI.

Experiments and calculations indicate that hydrogen fluoride electrochemical reactions are produced during battery charging, and lithium fluoride is converted from electrolyte to solid state and hydrogen is produced. Such reactions rely heavily on electrode materials such as graphite, graphene, and metals., prove the importance of battery catalysts.

The team also developed a new method for detecting hydrogen fluoride concentrations. Since hydrogen fluoride is a harmful substance formed by moisture and lithium salt(LiPF6), this detection method is key to SEI's future scientific research. Researcher NenadMarkovic said that the study will be tested at the BMW Battery Research Center in the future. The next step in the study is to design a new lithium-ion battery technology that will open up another road for lithium ion batteries today.

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