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|Title:||Multinuclear NMR Studies of Ion Mobility Pathways in Cathode Materials for Lithium Ion Batteries|
|Authors:||Davis, Linda J.|
|Advisor:||Goward, Gillian R.|
Bain, Alex D.
|Department:||Chemistry and Chemical Biology|
|Keywords:||lithium ion battery;cathode;MAS NMR;solid-state;paramagnetic shift;Materials Chemistry;Physical Chemistry;Materials Chemistry|
|Abstract:||<p>This thesis investigates the structure and ion mobility properties within the phosphate and fluorophosphate family of cathode materials for Li ion batteries using solid-state NMR. Developments in lithium ion battery technology are now directed towards automotive applications meaning that many of the cost and safety issues associated with current lithium ion battery technology need to be addressed. Within the current systems the high cost is largely attributed to the use of LiCoO<sub>2</sub> as the positive electrode. Many new and inexpensive Li intercalation materials have been put forward as alternatives to LiCoO<sub>2</sub>, however the details concerning the structural and ion-transport properties of these new phases are not well defined. <sup>6,7</sup>Li, <sup>31</sup>P, and <sup>19</sup>F NMR measurements are an ideal tool to study these properties, as <sup>6,7</sup>Li is able to probe the local environment and dynamics of the mobile ion while <sup>31</sup>P and <sup>19</sup>F monitor changes in the host framework. Materials selected for study in this thesis include olivine LiFePO<sub>4</sub>, monoclinic Li<sub>3</sub>M<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> (M = V, Fe), the tavorite-based Li<sub>2</sub>VPO<sub>4</sub>F and Li<sub>2</sub>VOPO<sub>4</sub>, and the novel layered Li<sub>5</sub>V(PO<sub>4</sub>)<sub>2</sub>F<sub>2</sub>. The fluorophosphates have been introduced as higher voltage cathode materials for lithium batteries, however our <sup>6,7</sup>Li 1D selective inversion and 2D EXSY measurements reveal timescales of ion hopping that are relatively slow when compared to those measured in the phosphates. This indicates that the improved power output from the voltage gains may be lost to slow charge/discharge rates.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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