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Characterization of Surface Free Energy of Cathode Materials for Lithium-ion Batteries

Title
Characterization of Surface Free Energy of Cathode Materials for Lithium-ion Batteries
Authors
Lee, Jun Min
DGIST Authors
Lee, Jun Min; Lee, Ho Chun
Advisor(s)
Lee, Ho Chun
Co-Advisor(s)
Choi, Su An
Issue Date
2013
Available Date
2016-05-18
Degree Date
2013. 8
Type
Thesis
Keywords
Lithium-ion batteriesLiMn2O4LiCoO2Metal dissolutionSurface free energyPolarity금속용출표면자유에너지결정구조최적화극성
Abstract
While the lithium-ion batteries (LIBs) are expanding their application area from mobile IT devices to the large scale power sources for electric vehicles and renewable energy storages, the limited cycle life of the present LIBs has been pointed out as the main obstacle. The degradation of LIBs employing LiMn2O4 and LiCoO2 cathode materials is known to be initiated by the metal dissolution from the cathode materials. Owing to the slow kinetics of the metal dissolution behavior, the quantitative analysis of the trace amounts of dissolved metal ions has been relied on the spectroscopic techniques such as the inductive coupled plasma (ICP) or the atomic adsorption spectroscopy (AAS). These conventional methods take at least several days and fail to provide any information on the cathode surface properties. We herein report that the SFE of cathode materials is closely related to their metal dissolution behavior. The SFEs of various types of LiCoO2 and LiMn2O4 are obtained by the contact angle measurement: the liquid adsorption method for powder samples and the sessile drop method for electrode samples. We confirm that the metal dissolution is determined dominantly by the polar component of the SFE of the cathode surface. We also found that the Al2O3 coating suppresses the metal dissolution, which is ascribed to the deceased polarity of cathode surface. The basic polarity of cathode electrodes is smaller than that of powders, which suggests a possibility that the metal dissolution can be suppressed through the optimization of the composite electrode components (binders and conductive carbons). We also confirmed the correlation of the SFEs with the types of crystal structures, which was examined by using SEM and XRD analysis. ⓒ 2013 DGIST
Table Of Contents
1. Introduction 1 -- 1.1 Overview 1 -- 1.2 Theory of surface free energy calculation by contact angle measurement 2 -- 1.3 Capillary rising method for porous materials 8 -- 1.4 Dissolution mechanism of cathode materials for Li-ion batteries 10 -- 1.5 Influence of cathode crystal structure to metal dissolution 11 -- 1.6 Examples of surface free energy usages to analyze the characteristics of Li-ion batteries 12 -- 2. Experimental 13 -- 2.1 Sessil drop method 13 -- 2.2 Adsorption method 15 -- 2.3 Measurement of metal dissolution 18 -- 3. Results and discussion 19 -- 3.1 Correlation of the surface free energies of LiMn2O4 powder with Mn dissolution 19 -- 3.2 Correlation of the surface free energies of LiMn2O4 electrode with Mn dissolution 21 -- 3.3 Analysis the crystal structures of LiMn2O4 23 -- 3.4 Correlation of the surface free energies of LiMn2O4 by increasing Al2O3 coating amount with Mn dissolution 26 -- 3.5 Acid and base part separation of polar surface free energy of LiMn2O4 28 -- 3.6 Correlation of the surface free energies of LiCoO2 powder with Co dissolution 30 -- 3.7 Correlation of the surface free energies of LiCoO2 electrode with Co dissolution 32 -- 3.8 Correlation of the surface free energies of LiCoO2 by increasing Al2O3 coating amount with Co dissolution 33 -- 3.9 Acid and base part separation of polar surface free energy of LiCoO2 35 -- 4. Conclusions 36 -- References 37 -- Summary (국문요약) 38
URI
http://dgist.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002262506
http://hdl.handle.net/20.500.11750/1340
DOI
10.22677/thesis.2262506
Degree
Master
Department
Energy Systems Engineering
University
DGIST
Files:
Collection:
Energy Science and EngineeringThesesMaster


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