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N3.02 - Polyanionic Li-Ion Battery Cathodes: Thermodynamic Stabilities of LiMSO4OH (M = Co, Fe, Mn) 
April 22, 2014   2:00pm - 2:15pm

Lithium hydroxysulfates with general formula LiMSO4OH (M = Co, Fe, Mn) have been advanced as a sustainable option to overcome the deleterious effects of the F-based cathode materials. These hydroxysulfates crystallize either in tavorite or in layered structure depending on the synthetic approach used to obtain these phases. The electrochemical behavior did not show any obvious correlation to structural characteristics such as bond iconicity or bond length. We determined the relative thermodynamic stabilities of LiMSO4OH (M = Co, Fe, Mn) using isothermal acid solution calorimetry to understand the observed differences in their synthesis, structure and electrochemical properties. Both redox potential and thermodynamic stability in layered LiMSO4OH (M = Co, Fe, Mn) decrease with decrease in sulfate binding symmetry as one moves from Co to Mn and LiMnSO4OH becomes electrochemically inactive. LiFeSO4OH shows anomalous stability among isostructural layered materials. Tavorite LiFeSO4OH was found to be energetically less stable than layered LiFeSO4OH, possibly due to its lower symmetry corner shared octahedral chain structure. This study demonstrates the correlation between energetic and redox potential trends in LiMSO4OH (M = Fe, Co, Mn) materials with their ionic radius, overall structure symmetry as well as sulfate binding symmetry.

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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