This student-run monthly series spotlights the latest research from Stanford, presented by PhD candidates and postdocs. Registration is required, and is free and open to the public.

This month's speakers:

Il Rok Choi, Battery Researcher, Stanford University
"Asymmetric ether solvents for high-rate lithium-metal batteries"

Abstract:

Recent electrolyte solvent design based on weakening lithium-ion solvation have shown promise in enhancing cycling performance of Li-metal batteries (LMBs). However, they often face slow redox kinetics and poor cycling reversibility at high rate. Here, we report using asymmetric solvent molecules significantly accelerates Li redox kinetics. Asymmetric ethers (1-ethoxy-2-methoxyethane, 1-methoxy-2-propoxyethane) showed higher exchange current densities and enhanced high-rate Li⁰ plating/stripping reversibility compared to symmetric ethers. Adjusting fluorination levels further improved oxidative stability and Li⁰ reversibility. The asymmetric 1-(2,2,2-trifluoro)-ethoxy-2-methoxyethane, with 2 M lithium bis(fluorosulfonyl)imide, exhibited high exchange current density, oxidative stability, compact solid-electrolyte interphase (~10 nm). This electrolyte exhibited superior performance among state-of-the-art electrolytes, enabling over 220 cycles in high-rate Li (50 μm)||NMC811 (4.9 mAh cm^-2) cells and for the first time over 600 cycles in anode-free Cu||Ni95 pouch cells (200 mAh) under electric vertical take-off and landing (eVTOL) cycling protocols. Our findings on asymmetric molecular design strategy points to a new pathway towards achieving fast redox kinetics for high-power LMBs.

Bio: 

Il Rok Choi (Rok Choi) is a battery researcher specializing in electrolyte design for lithium-metal batteries. His work has advanced next-generation electrolyte formulations and solvent design to enable fast-charging and high-efficiency Li-metal anodes. With expertise in electrolyte synthesis, interfacial chemistry, and advanced characterization techniques, he has contributed to understanding and mitigating challenges such as dendrite formation and side reactions. Beyond fundamental research, he integrates cost analysis and market strategy to align scientific innovation with practical energy storage solutions. Passionate about pushing the boundaries of Li-metal battery technology, Rok Choi aims to develop safe, high-performance electrolytes for next-generation energy storage.

Registration is open to all and free.