421 0

Improvement of Low Temperature Cycling Performance of Li-ion cells by Employing Ester Solvent.

Title
Improvement of Low Temperature Cycling Performance of Li-ion cells by Employing Ester Solvent.
Author
Seung Hark Park
Alternative Author(s)
박승학
Advisor(s)
김동원
Issue Date
2019-02
Publisher
한양대학교
Degree
Master
Abstract
리튬이온전지의 저온성능향상을 위하여 carbonate계 전해질에 널리 쓰이는 dimethyl carbonate를 대신하여 ester계 용매인 ethyl propionate를 적용해 보았고, ethyl propionate의 부피 비를 달리한 4종의 전해질에 대하여 25℃와 -20℃에서 평가를 진행하였다. 사이클 실험 결과, 1.5M LiPF6 in ethylene carbonate/ethyl propionate 3/7 + fluoroethylene carbonate 5.0 wt.%전해질이 -20℃에서 가장 높은 방전용량과 우수한 사이클 성능을 보였다. 원인 규명을 위하여 이온전도도 측정 실험과 시차주사열량분석법을 통해 전해질 조성에 따른 저온 특성을 확인하였고, 전기화학적 임피던스 분광법을 활용하여 전해질의 구성에 따른 리튬 이온의 solvation/de-solvation에 필요한 활성화 에너지를 계산하였다. 분석 결과, ethyl propionate의 낮은 환원 안정성 때문에 두꺼운 SEI층이 형성되어 저항으로 작용하게 되지만, 낮은 solvation/de-solvation energy와 저온에서 더 높은 이온전도도를 갖게 되어 리튬 이온이 더 빠르게 전기화학반응에 참여할 수 있는 환경을 제공해주었기 때문에 향상된 저온 사이클 성능을 낼 수 있었다.
To improve the low temperature cycling performance of lithium ion battery, ethyl propionate (EP) was employed instead of dimethyl carbonate (DMC) widely used in commercial electrolytes. Electrolytes having different volume ratios of ethyl propionate were evaluated at 25℃ and -20℃. From the cycling test, we could confirm that 1.5M LiPF6 in ethylene carbonate (EC)/ethyl propionate 3/7 + fluoroethylene carbonate (FEC) 5.0 wt.% electrolyte exhibited highest discharge capacity and enhanced cycling performance at -20℃. To reveal the origin of this result, low temperature characteristics of the electrolytes with various composition were investigated by ionic conductivity measurement and differential scanning calorimetry. The activation energy required for the solvation/de-solvation process of lithium ion was calculated by using electrochemical impedance spectroscopy. These results demonstrated that improved low temperature cycling performance can be ascribed to low solvation/de-solvation energy and higher ionic conductivity of EP.
URI
https://repository.hanyang.ac.kr/handle/20.500.11754/99839http://hanyang.dcollection.net/common/orgView/200000434570
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > CHEMICAL ENGINEERING(화학공학과) > Theses (Master)
Files in This Item:
There are no files associated with this item.
Export
RIS (EndNote)
XLS (Excel)
XML


qrcode

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

BROWSE