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Correlation Study of Surface Energy of Electrodes and Electrolytes with Lithium Ion Battery Performance

Title
Correlation Study of Surface Energy of Electrodes and Electrolytes with Lithium Ion Battery Performance
Translated Title
전극 및 전해질 물질의 표면에너지와 리튬이온배터리 성능의 상관관계 연구
Authors
Lee, Hye Jin
DGIST Authors
Lee, Hye Jin; Lee, Ho Chun; Kang, Joon Goo
Advisor(s)
Lee, Ho Chun
Co-Advisor(s)
Kang, Joon Goo
Issue Date
2016
Available Date
2016-02-12
Degree Date
2016. 2
Type
Thesis
Keywords
LiMn2O4Surface free energymetal dissolutiongraphite electrodeSEIcondition number표면자유에너지금속용출흑연전극
Abstract
Despite the huge success of the lithium-ion batteries (LIBs) in the portable electronic devices and electric vehicles (EVs) applications, the fundamental understanding on the electrode/electrolyte interface still remains challenging. The interfacial phenomena are governed by the physico-chemical properties of the electrode surface as well as the nature of electrolyte components. At the first part of this work, the surface free energy (SFE) analysis is performed for various commercial grade LiMn2O4 (LMO) powders and the three SFE components, Lifshitz van der Waals (γ𝑠LW), acid(γ𝑠+), and base(γ𝑠−), are obtained based on the van Oss-Chaudhary-Good (vOCG) theory. It is revealed that Mn dissolution is strongly correlated with the Lewis acid-base component (γ𝑠AB = 2√γ𝑠+ ∙ γ𝑠− ), which is attributed to the short-range columbic interactions between the Lewis acidic site of LMO surface (γ𝑠+) and the basic electrolyte species (e.g., solvents, anions), and between the Lewis basic site (γ𝑠−) and the acidic electrolyte species (e.g., HF). At the second part, the SFE analysis is performed to shed some light on surface chemical properties of graphite anode and the solid-electrolyte interphase (SEI) layer formed on it. The edge and basal planes of pristine graphite show relatively high γ+ and γ-, respectively. The presence of SEI layer brings dramatic difference in the SFE properties of the graphite electrodes. In particular, the γ- values becomes one order of magnitude higher. In addition, the SFE values also depend on the types of Li salt employed for SEI formation. LiPF6 and LiFSI solutions form inorganic-rich SEI layer, and thus higher total SFE than the organicrich SEI formed in a LiClO4 solution. At the last part, various polymers are examined to search a suitable probe solid triplet with a low condition number, which is mandatory to determine the three SFE components of liquid samples. Among the tested combinations, PE/PVF/PMMA set is found to have the lowest condition number, which is rather high compared to that of probe liquid set. Further exploration for better probe solid triplet is needed. ⓒ 2016 DGIST
Table Of Contents
Ⅰ. Correlation of surface free energy and electrolyte property to assess metal dissolution behavior of LiMn2O4 1-- 1.1 Introduction 1-- 1.1.1 Overview 1-- 1.1.2 Capillary rising method for porous materials 2-- 1.2 Experimental 3-- 1.2.1 Preparation of LMO electrodes 3-- 1.2.2 Metal dissolution 4-- 1.2.3 Activation energy of Mn dissolution reaction and Arrhenius equation 5-- 1.2.4 Adsorption method 7-- 1.3 Results and discussion 11-- 1.3.1 Analysis of the morphology of LiMn2O4 11-- 1.3.2 Contact angle measurement by sorption and surface energy 12-- 1.3.3 Effect of donor number on the Mn dissolution 16-- 1.3.4 Effect of HF content and Mn dissolution 19-- 1.3.5 Correlation between surface energy components and Mn dissolution 20-- 1.4 Conclusions 20-- Ⅱ. Surface energy analysis of pristine and SEI-formed graphite anodes 24-- 2.1 Introduction 24-- 2.2 Experimental 24-- 2.2.1 Surface energy analysis of pristine graphite 29-- 2.2.2 SEI formation 31-- 2.3 Results 32-- 2.3.1 Surface energy analysis of graphite (edge and basal planes) 32-- 2.3.2 Surface energy analysis of SEI on the pyrolytic graphite 33-- 2.4 Conclusion and future plan 39-- Ⅲ. Solid surface energy analysis of polymers for solid probes 42-- 3.1 Introduction 42-- 3.2 Experimental 48-- 3.3 Results 51-- 3.4 Discussion and future plan 54-- References 56
URI
http://dgist.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002231309
http://hdl.handle.net/20.500.11750/1459
DOI
10.22677/thesis.2231309
Degree
Master
Department
Energy Systems Engineering
University
DGIST
Files:
Collection:
Energy Science and EngineeringThesesMaster


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