В Сколтехе раскрыли значение важного компонента электролитов для литий-ионных аккумуляторов.

The study has been published in the Journal of Materials Chemistry A. In the early stages of lithium-ion battery commercialization, researchers faced the challenge of corrosion in graphite anodes: electrolytes based on propylene carbonate (PC) interacted well with metallic lithium but proved to be extremely aggressive towards graphite.

This hindered the use of graphite electrodes until ethylene carbonate (EC) was proposed as an alternative solvent in the electrolyte formulation. Despite the similarities between the molecules of EC and PC from an electrochemical perspective, they exhibit different behaviors regarding graphite anodes. The nature of this difference and the behavior of the "magic solvent" EC have been the subjects of numerous studies and discussions over the decades, yet a consensus among scientists has yet to be reached.

Moreover, this question is not purely theoretical; the answer will be significant in the design of batteries, particularly concerning the choice of solvent in the electrolyte composition.

In their article, Senior Researcher Sergey Luchkin and Lead Manufacturing Engineer Yegor Pazhetnov from the Skoltech Center for Energy Technologies proposed that the presence of EC in the electrolyte leads to the formation of a thin layer of highly viscous liquid on the surface of graphite. This layer protects the graphite from corrosive delamination. Subsequent experiments confirmed that such a layer does indeed form in EC-based electrolytes and is absent when using PC.

Notably, this viscous liquid layer appears before the formation of a crucial component of lithium-ion batteries—the so-called solid electrolyte interphase (SEI)—and therefore should influence the process of its formation. The solid electrolyte interphase is a thin film of solid electrolyte that forms on the surface of the anode during the initial charge and discharge of the battery at the factory. This film prevents both the degradation of the graphite anode and the electrolyte recovery—a process that deteriorates the performance of the device.

This new perspective on interfacial processes in lithium-ion batteries opens up new avenues for understanding the relationship between electrolyte composition and interfacial dynamics between the electrolyte and anode, which is critical for developing more stable and efficient batteries.

The approach proposed in the study is applicable not only to widely used lithium-ion batteries but also to the emerging sodium- and potassium-ion batteries. The issue of solid electrolyte interphase formation is relevant for these energy storage technologies as well. The work of the Skoltech researchers provides a deeper understanding of how the physical properties of electrolyte components influence interfacial processes, potentially accelerating innovations in energy storage.

The study highlighted in the press release is supported by a grant from the Russian Science Foundation.