<p>Lithium-ion batteries provide a more cost-effective and non-toxic source of reusable energy compare to other energy sources. Several research studies have lead to production of some more promising cathode components for lithium ion batteries. Recently, a new series of pyrophosphate-based composition Li<sub>2</sub>FeP<sub>2</sub>O<sub>7</sub> and Li<sub>2</sub>MnP<sub>2</sub>O<sub>7</sub> has been reported as cathode materials. They have shown a 3D framework structure and the two Lithium-ions in the three-dimensional tunnel structure make it possible that more than one lithium ion be extracted during cycling. Lithium solid state nuclear magnetic resonance (NMR) is an effective technique to study this cathode material, not only for analyzing local structure, but also for investigation of the microscopic processes that take place in the battery.</p> <p>In this work, Li<sub>2</sub>FeP<sub>2</sub>O<sub>7</sub> and Li<sub>2</sub>MnP<sub>2</sub>O<sub>7</sub> have been synthesized. The lithium environment of these materials is studied using 1D <sup>6,7</sup>Li NMR. Assignment of Li<sub>2</sub>MnP<sub>2</sub>O<sub>7</sub> spectrum has been made based on Fermi-contact interaction and crystal structure. Both variable temperature experiment and 1D selective inversion NMR are used to establish Li-ion pathways as well as Li hopping rates for Li<sub>2</sub>MnP<sub>2</sub>O<sub>7</sub>. Also, <sup>7</sup>Li MAS NMR measurements are used to characterize Li environments in LixFeP<sub>2</sub>O<sub>7 </sub>after being electrochemically cycled to different points, and preliminary results regard to changes to ion mobility in LixFeP<sub>2</sub>O<sub>7 </sub>at different electrochemical cycled points are presents here, solid-solution (de)lithetiation process is confirmed for this material.</p> / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/12796 |
| Date | 04 1900 |
| Creators | He, Xuan |
| Contributors | Goward, G.R., Peter Kruse; Yurij Mozharivskyj, Chemistry |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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