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N6.14 - First-Principles Study of Structure and Electrochemistry of LiCoSiO Polymorphs 
April 24, 2014   11:45am - 12:00pm

Due to high voltage and theoretical capacity over 300 mAh/g, LiCoSiO is a promising compound of polyoxyanion cathode materials for lithium ion batteries. However, LiCoSiO presents obscuring complex polymorphism and unusual difficulty to realize a practical electrochemistry. Here, we report first-principles computations in coupling with simulated Xrd to characterize structures and electrochemical properties of LiCoSiO (x=2, 1.5, 1) with symmetries Pmn2, Pbn2 and P2/n. The calculated Xrd spectra and voltage profiles agree well with available experimental results. We show that the CoO tetrahedra, as the key units, present their fingerprint in the Xrd spectra and determine electrochemical behaviors of LiCoSiO polymorphs. Spin ordering and Xrd spectra of bonding characteristic associated with the oxidation of CoO tetrahedra are predicted for further experimental investigation. Delithiated phases are intrinsic Mott insulators. The swapping of insulating gap states during delithiation correlates with the contraction of the oxidized CoO units, demonstrating the occurring of Peierls distortions. The resulting electron localization is responsible for capacity quality degrading. Our results provide guidance for further realization of high performance polymorphs suitable for applications.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis