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Development of Electrolytes for Improving Electrochemical Performances of High-voltage LiNi0.5Mn1.5O4.

Title
Development of Electrolytes for Improving Electrochemical Performances of High-voltage LiNi0.5Mn1.5O4.
Translated Title
Linear carbonate 종류에 따른 LiNi0.5Mn1.5O4 양극의 전기화학적 성능에 미치는 영향
Authors
Nam, Ye Seol
DGIST Authors
Nam, Ye Seol; Lee, Ho Chun; Kim, Jae Hyeon
Advisor(s)
Lee, Ho Chun
Co-Advisor(s)
Kim, Jae Hyeon
Issue Date
2017
Available Date
2017-01-18
Degree Date
2017. 2
Type
Thesis
Keywords
Li-ion batteriesLiNi0.5Mn1.5O4HFlinear carbonateoxidation stability
Abstract
Currently there is an urgent need to maximize the energy density of lithium ion batteries (LIBs). LiNi0.5Mn1.5O4 (LNMO) is a promising candidate for the high-energy LIBs due to its high operating voltage, low price, and reasonable capacity. However, LNMO suffers from anodic decomposition of the electrolyte under high-voltage operation, leading to severe capacity fading. Here, we examine the effects of linear carbonates (LC: DMC, DEC, and EMC) in 1 M LiPF6 EC/LC (3/7, v/v) on LNMO/graphite, LNMO/Li, and graphite/Li cells. We also investigate LNMO symmetric cell test in cycle at 60 oC because the use of symmetric cells complementarily suggests that transition metal dissolution is mainly responsible for the LNMO/electrolyte interface degradation. The LNMO cells with EC/DMC show better cyclability and coulombic efficiency at 25 oC, 55 oC and 60 oC than those with EC/EMC and EC/DEC. Also, the cells with EC/DMC exhibit superior self-discharge suppression at 60 oC to other compositions. The improved performances in the cells with EC/DMC are attributed to diminished HF formation compared to the others, which is evidenced by both HF titration and surface analysis of LNMO using X-ray photoelectron spectroscopy (XPS). Also, through LSV analysis, Oxidation stability of EC/DMC is higher than EC/EMC and EC/DEC. ⓒ 2017 DGIST
Table Of Contents
1. INTRODUCTION 1-- 2. METHODS AND MATERIALS 4-- 2.1. Chemicals and Electrode Preparation 4-- 2.2. Coin-type Cell Assemble 5-- 2.3. LNMO/LNMO Symmetric Cell 5-- 2.4. Graphite/Graphite Symmetric Cell 6-- 2.5. X-ray Photoelectron Spectroscopy 6-- 2.6. HF and H2O Content Measurements 6-- 2.7. Linear Scanning Voltammetry 7-- 3. RESULTS 7-- 3.1 The Effect of the Linear Carbonate on LNMO/Graphite full cell 7-- 3.2 The Effect of the Linear Carbonate on LNMO 11-- 3.3 The Effect of the Linear Carbonate on Graphite 13-- 3.4 The Effect of the Linear Carbonate on Lithium Metal 16-- 3.5 Surface Composition Analysis of LNMO with Linear Carbonates 16-- 3.6 Linear Carbonate Effect of HF Formation at High Temperature 20-- 3.7 Oxidation Potential according to Linear Carbonates 21-- 4. CONCLUSION 22
URI
http://dgist.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002326903
http://hdl.handle.net/20.500.11750/1491
DOI
10.22677/THESIS.2326903
Degree
Master
Department
Energy Systems Engineering
University
DGIST
Files:
Collection:
Energy Science and EngineeringThesesMaster


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