Development of Next-Generation Electrolyte for Uniform Lithium Metal Growth
The results showed uniform growth of lithium metal regardless of surface roughness.

The results obtained by Professor Seung-Ho Yu’s group were published in ACS Energy Letters.

▲ Professor Seung-Ho Yu of the Department of Chemical and Biological Engineering in the College of Engineering.

Professor Seung-Ho Yu’s group of the Department of Chemical and Biological Engineering in the College of Engineering conducted a joint study with research groups of Seoul National University and Cornell University, and developed a next-generation electrolyte for the uniform growth of lithium metal. Professor Yu’s group effectively demonstrated the excellent characteristics of the next-generation electrolyte through operando imaging based on visible light and X-ray, thereby increasing the possibility of the commercialization of lithium metal electrodes.

Lithium metal is considered to be an ideal anode material for high-performance secondary batteries, because it has both a theoretical capacity (3,860 mAh/g) more than 10 times higher than that of graphite, which is used in lithium-ion batteries, and a low electrochemical potential (-3.040 V vs. standard hydrogen electrode (SHE)). However, repeated charge/discharge reactions cause the lithium to grow locally to produce dendrite structures. This dendrite growth of lithium can cause short circuits in batteries, and thereby safety issues, such as battery explosions. In addition, the dendrite growth can be associated with extreme volumetric changes that can lead to irreversible decreases in performance. Therefore, suppressing the dendrite growth of lithium is critical to the commercialization of lithium metal batteries.

In the present study, a novel concept electrolyte was provided by mixing to an appropriate ratio carbonate-based materials, which are widely applied to conventional lithium-based secondary batteries, with ether-based materials. The newly developed electrolyte showed substantially higher ion conductivity and lithium-ion yield than the existing commercial electrolytes. Surface analysis revealed the excellent mechanical and chemical properties of the solid electrolyte interface (SEI) layer generated between the electrolyte and the lithium metal interface. Furthermore, a drastic improvement in battery performance was verified through charge/discharge experiments.

 

▲ Illustration of the different lithium growth patterns in the next-generation electrolyte and in commercially available electrolyte; and the corresponding results obtained by operando X-ray imaging.

Professor Yu’s group directly observed the lithium metal growth, dependent on the electrolyte, through operando imaging based on radiational X-ray and visible light. In addition, the research group investigated the mechanism of lithium metal growth by combining the imaging method with various electrochemical analyses. The analytical results provided the unique finding that the lithium growth was irrelevant to the surface roughness of the current collector under specific electrolyte conditions. This presented the possibility of utilizing the wide surface area of a three-dimensional current collector to the full.

This study was jointly conducted with Yunseo Jeoun, a student in the Master’s and & Doctoral Degree Combined Program (first author, Seoul National University), Dr. Kookahn Kim (first coauthor, Seoul National University), Professor Yung-Eun Sung (co-corresponding author, Seoul National University) and Professor Hector Abruna (co-corresponding author, Cornell University). The results of the study were published in ACS Energy Letters (IF=23.101) on June 6, 2022.

Professor Yu said, “We were able to effectively suppress the dendrite growth, which is a chronic problem in lithium metal electrodes, by applying the next-generation electrolyte developed in our study. We expect that the excellent electrochemical properties and SEI characteristics can make significant contributions to the commercialization of lithium metal electrodes.”