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서효리,성백석,김건,이철우 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5
The structural change during electrochemical cycling in full-cell system has been investigated by neutron diffraction methodand the full-cell consists of spinel-lithium manganese oxide cathode and graphite anode. The structural variation has beenmonitored by in-situ neutron diffraction technique at different state of charges (SOCs), and the obtained data were comparedwith ex-situ powder neutron diffraction patterns. Phase transitions for lithiated/delithiated graphite can clearly explain thatthe intercalated lithium ions in graphite are not perfectly extracted during a delithiaion process. The content of LiC12 phaseincreases as an increase in electrochemical cycle numbers, and the lattice parameter of LiMn2O4 also decreases due to thereduction of the amounts of Li ions, which can be reversibly intercalated/deintercalated into/from the structure.
서효리,나수빈,이보은,임태은,오시형 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.64 No.-
Spinel-structured lithium manganese oxides are considered as promising cathode material, however, their widespread commercial application remains hampered by their poor surface instability. To overcome these problems, we designed and synthesized task-specific ionic liquid additives that can effectively scavenge trace amounts of fluoride in the cell. Addition of ionic liquid additives in the electrolyte significantly improves cycling retention. 1H- and 19F-nuclear magnetic resonance spectroscopy measurements and inductively coupled plasma mass spectrometry elemental analysis collaboratively provides clear evidence that the ionic liquid additives selectively suppress parasitic reactions of the electrolyte with the surface of lithium manganese oxides cathode.
Surface-initiated fluoride-scavenging polymeric layer on cathode materials for lithium-ion batteries
서효리,이해리,강동구,임태은,오시형 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-
Spinel-structured lithium manganese oxides (LMOs) suffer from manganese dissolution at elevated temperatures, which leads to severe capacity fading. In this work, a novel strategic approach was developed to alleviate this phenomenon by using poly(dimethylsiloxane) (PDMS) as a simple and scalable electrode additive. LMO electrodes containing finely dispersed PDMS were prepared using a conventional electrode coating process. Electrochemical studies showed that the PDMS-dispersed LMO electrodes had significantly improved cycling retentions. Ex-situ FT-IR and 19F NMR spectra indicated PDMS chemically scavenged the F species, which cause manganese dissolution in LMO-based cells. In addition, a plausible mechanism was proposed based on the spectroscopic evidences.