| dc.contributor.author | Obrovac, Mark Nikolas. | en_US |
| dc.date.accessioned | 2014-10-21T12:37:22Z | |
| dc.date.available | 2001 | |
| dc.date.issued | 2001 | en_US |
| dc.identifier.other | AAINQ75716 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55868 | |
| dc.description | This thesis discusses two aspects of nanograined electrode materials for lithium batteries. Firstly the size and surface effects in nanosized lithium intercalation materials is explored. Nanosized intercalation materials are modelled using Monte Carlo simulations of finite sized lattice gases. This study shows that finite size intercalation materials can have marked differences in their voltage-composition behaviour compared to their bulk counterparts. The finite size of the lattices tends to cause a rounding-off of voltage plateaus, while surface effects cause extra plateaus to appear in voltage curves and can also cause phase transitions to occur at different voltages than they do in the bulk. Attempts at making real nanosized intercalation materials proved difficult by standard laboratory methods. A nanograined lithium manganese oxide was prepared in aqueous solution, however. This material has an interesting microstructure, being composed of 7 nm grains which self-assemble into 50 nm squares and rectangles. The voltage behaviour of this material is similar to that of lithium rich LiMn2O4 spinel, but has capacity between 3.3 V and 3.8 V, where no capacity exists in bulk LiMn2O 4. The voltage plateaus of this material are also sloped and rounded off. It is unclear if these effects are caused by surface and size effects or by lattice defects in the structure. | en_US |
| dc.description | The second focus of the thesis explores the mechanism and applications of displacement electrodes for secondary lithium cells. Such electrodes do not intercalate lithium, but undergo a reversible displacement reaction during cycling. It was found that non-intercalating transition metal oxide electrodes are displaced by lithium on the first discharge to form a nanocomposite of lithia and reduced transition metal. During charge lithium is removed from this composite, while concurrently the transition metal enters the oxygen lattice of the lithia. This process is thought to resemble an ion-exchange mechanism. It is also shown that a nanocomposite of lithia and transition metal made by ball-milling contains electrochemically active lithium. Such materials have a huge capacity (∼500 mAh/g) compared to conventional intercalation cathodes. These composites might find application in lithium batteries as high capacity cathode materials or as an additive to provide a source of lithium for conventional anodes which suffer from irreversible capacity or for cathodes that can uptake more lithium than they contain as made. Finally, the ion-exchange mechanism discussed for displacement type electrodes was attempted outside of the cell by reacting Li2O with transition metal ions in nonaqueous solvents. Although a reaction occurred, it was difficult to tell if an ion exchange type reaction took place or if a water impurity was the cause of the reaction. Nevertheless such a reaction was shown to take place very slowly in solution, if it occurs at all. Because of this, binary lithium compounds other than Li2O in which the reaction does take place more quickly, such as Li2S, are suggested as better candidates for electrochemical displacement type electrodes. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2001. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Physics, Condensed Matter. | en_US |
| dc.subject | Energy. | en_US |
| dc.title | Nanostructured electrode materials for lithium ion batteries. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
