Sabrina Chun Yan Wong
Pronouns: she/her
Research Mentor(s): Yiyang Li
Research Mentor School/College/Department: Materials Science & Engineering / Engineering
Program: UROPF
Session: Session 7 (4:40pm – 5:30pm)
Authors:
Abstract
Conventional commercial Li-ion battery cathodes are composed of polycrystalline LiMeO2 battery particles, where Me is a combination of Ni, Mn, and Co. These cathodes are often referred to as NMC. An alternative to polycrystalline NMC is single-crystal NMC, which not only offers substantially improved cycle life but also enables more precise fundamental studies due to its well-defined morphology. This project aims to synthesize single-crystal NMC that is better controlled in chemistry, size, and morphology compared to its polycrystalline counterpart. The target NMC would have more consistent and measurable differences in its physical properties, which can then be correlated with differences in electrochemical performance. We adapted and experimentally tested existing procedures for synthesizing NMC via molten-salt synthesis, varying the synthesis parameters over multiple trials, to determine the ideal conditions for synthesizing NMC in the shape of truncated octahedrons about 10µm in diameter. After each trial, we analyzed the NMC particles using scanning electron microscopy for size and morphology, energy-dispersive X-ray spectroscopy for chemical composition, and X-ray diffraction for crystal structure. Our results currently show that using cesium chloride as the flux produces truncated octahedral NMC and that higher temperatures and longer reaction times increase the size of NMC. One shortcoming is that it is difficult to synthesize NMC larger than 5-6µm in diameter. The ability to determine the ideal synthesis conditions for the desired NMC would enable the synthesis of consistent and reproducible samples. These samples can then be used to understand their electrochemical variability, which in turn can aid the development of future Li-ion batteries.
