Stanford Energy Student Lectures: Sang Cheol Kim and Xi Chen

San Cheol Kim

Title: High entropy electrolytes for practical lithium metal batteries

Abstract: Electrolyte engineering is crucial for improving battery performance, particularly for lithium metal batteries. Recent advances in electrolytes have greatly improved cyclability by enhancing electrochemical stability at the electrode interfaces, but concurrently achieving high ionic conductivity has remained challenging. Here we report an electrolyte design strategy for enhanced lithium metal batteries by increasing the molecular diversity in electrolytes, which essentially leads to high entropy electrolytes (HEEs). We find that the entropy effect reduces ion clustering while preserving the characteristic anion-rich solvation structures. Electrolytes with smaller-sized clusters exhibit a 2-fold improvement in ionic conductivity compared to conventional weakly-solvating electrolytes, enabling stable cycling at high current densities up to 2C in anode-free NMC622 || Cu pouch cells.

Bio: Sang Cheol Kim completed his undergraduate studies at Duke University, with degrees in Mechanical Engineering and Materials Science (MEMS) and Chemistry. After three years at LG Chem, designing and developing battery cells for electric vehicles, he moved to Stanford, where he received MS and PhD degrees in Materials Science and Engineering. During his graduate studies, Sang Cheol worked with Prof. Yi Cui to develop tools to probe the liquid electrolyte in batteries, and developed a new class of electrolytes called the high entropy electrolyte. Currently, Sang Cheol is a Stanford Energy Postdoctoral Fellow, working with Prof. Steven Chu on developing electrochemical solutions for energy and sustainability.

Xi Chen

Title: Evaluating and developing separation technologies for lithium-ion battery recycling

Abstract: The rising demand of sustainable energy significantly exceeds the current supply capacity, and recycling lithium-ion batteries (LIBs) is a critical step towards building a circular battery supply chain. Sustainable LIB batteries require efficient separation, while existing separation technologies suffer from high energy intensities and inadequate separation precision, and lack appreciation of the tradeoffs between water and energy consumption in industrial-scale operations. In this talk, I will present life-cycle analyses of water–energy impacts of industrial-scale lithium-ion battery (LIB) recycling, and development of membrane materials for high-purity lithium extraction. My work identifies that separation technologies play a critical role in reducing the environmental impacts of LIB recycling, and I employ the knowledge from my mechanistic studies to design membrane materials for selective extraction of lithium element from magnesium and sodium.

Bio: Dr. Xi Chen is currently a postdoctoral fellow in The Department of Chemical Engineering at Stanford University, working with Prof. William A. Tarpeh. He received his Ph.D. in Environmental Engineering at Columbia University in 2020. Dr. Chen focuses his research on advancing separation technologies for addressing global water-energy-environment challenges. His past studies include novel contributions toward 1) evaluating and developing technologies for recycling lithium-ion batteries, 2) management and treatment of high-salinity brines for clean water production, 3) energy conversion of low-temperature heat resources, and 4) advancing fundamental transport theory for polymer membranes. Dr. Chen holds a Master’s degree in Environmental Engineering from University of Illinois at Urbana-Champaign, and received his B.S. in Environmental Science from Nankai University in China.