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Yang Shao-Horn. Appapillai, Anjuli T. (Anjuli Tara) Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Massachusetts Institute of Technology. Department of Mechanical Engineering 2007-02-21T12:03:45Z 2007-02-21T12:03:45Z 2006 2006 http://hdl.handle.net/1721.1/36195 76813409 Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. Includes bibliographical references (p. 101-108). AlPO₄-nanoparticle coated LiCoO₂ is studied as a positive electrode for lithium rechargeable batteries for a high-voltage charge limit of 4.7V. To understand the role of the coating in transport phenomena and in deintercalation of Li+, the electrochemical behavior is studied alongside the microstructure of the coating. The galvanostatic charge profile is studied with electrochemical impedance tests conducted at various lithium contents during charging. The coating is found to increase the flatness of the two-phase region plateau and to cause the appearance of the monoclinic distortion at x=0.5 as well as distinct plateaus for 03 to H1-3 and H1-3 to 01 transitions, indicating that application of the coating transformed Li-rich LiCoO₂ into stoichiometric LiCoO₂. According to electronic resistance (Re) values from impedance spectra, the coated LiCoO₂ has a more rapid decrease in Re with delithiation, and both materials show a rise in Re above 4.5V. Structurally, SEM images show pitted surface morphology only on the edges of the layers of coated LiCoO₂. (cont.) Furthermore, cross-sectional TEM images reveal a continuous coating layer with compositional variations seen through EDX mapping and point spectroscopy, indicating that a thin layer of aluminum covers the particle uniformly while the phosphorus is more concentrated in thicker, isolated clusters, which is further supported y XPS surface analysis. This coating composition may increase the ionic conductivity of the LiCoO₂ surface while protecting it from harmful side reactions and stabilizing the surface structure to inhibit Co dissolution. by Anjuli T. Appapillai. S.M. 113 p. eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Mechanical Engineering. Electrochemical and microstructural studies of AlPO₄-nanoparticle coated LiCoO₂ for lithium-ion batteries Thesis application/pdf false Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="18afaac6-f35b-47b1-a7f7-99b95aad4dd2"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Electrochemical and microstructural studies of AlPO₄-nanoparticle coated LiCoO₂ for lithium-ion batteries</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2006</PublicationDate> <Authors> <Author> <DisplayName>Appapillai, Anjuli T. (Anjuli Tara)</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Mechanical Engineering.</Keyword> <Abstract>AlPO₄-nanoparticle coated LiCoO₂ is studied as a positive electrode for lithium rechargeable batteries for a high-voltage charge limit of 4.7V. To understand the role of the coating in transport phenomena and in deintercalation of Li+, the electrochemical behavior is studied alongside the microstructure of the coating. The galvanostatic charge profile is studied with electrochemical impedance tests conducted at various lithium contents during charging. The coating is found to increase the flatness of the two-phase region plateau and to cause the appearance of the monoclinic distortion at x=0.5 as well as distinct plateaus for 03 to H1-3 and H1-3 to 01 transitions, indicating that application of the coating transformed Li-rich LiCoO₂ into stoichiometric LiCoO₂. According to electronic resistance (Re) values from impedance spectra, the coated LiCoO₂ has a more rapid decrease in Re with delithiation, and both materials show a rise in Re above 4.5V. Structurally, SEM images show pitted surface morphology only on the edges of the layers of coated LiCoO₂.</Abstract> <Abstract>(cont.) Furthermore, cross-sectional TEM images reveal a continuous coating layer with compositional variations seen through EDX mapping and point spectroscopy, indicating that a thin layer of aluminum covers the particle uniformly while the phosphorus is more concentrated in thicker, isolated clusters, which is further supported y XPS surface analysis. This coating composition may increase the ionic conductivity of the LiCoO₂ surface while protecting it from harmful side reactions and stabilizing the surface structure to inhibit Co dissolution.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>