Ni-MH battery today is one of the most widely used secondary battery type because of its properties like secure use at high voltages, excellent thermal properties and consisting of environmentally acceptable materials. LaNi5, as an anode material, is the dominant commercial active material for the Ni-MH battery industry. CaNi5, belonging to same crystal structure, is an alternative for LaNi5, due to higher hydrogen storage capacity, higher theoretical discharge capacity, light weight and low cost. However, low cycle life is the main restriction for the use of CaNi5. In this study, effects of alloying was studied using an ab initio pseudo potential method. In this regard, formation energies of the CaNi5 compounds having different alloying elements were calculated for the understanding of the effect of the alloying element on the stability of the compound. It was found that, all lanthanides and actinides and early transition metals (Sc, Y, Zr, Hf) replacing Ca and early transition metals (Sc, Ti, Zr, Hf) plus elements like Al, Si, P, Ge, Zn, Sn and Sb replacing Ni, decrease the formation energy of CaNi5. Lower formation energy, compared to the pure compound, increases the stability which could improve the cyclic durability of CaNi5 to be used as an anode in Ni-MH batteries. In addition, in order to investigate effects of alloying on Ca diffusion in CaNi5, activation energies of Ca diffusion for different alloys were calculated by Nudged Elastic Band method (NEB) method.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12614677/index.pdf |
| Date | 01 September 2012 |
| Creators | Mugan, Orkun |
| Contributors | Aydinol, Kadri |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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