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Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer
Dissertation (MSc (Physics))--University of Pretoria, 2023.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2023
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| _version_ | 1867613582098694144 |
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| access_status_str | Open Access |
| author2 | Mapasha, Refilwe Edwin |
| author_browse | Mapasha, Refilwe Edwin |
| author_facet | Mapasha, Refilwe Edwin |
| collection | Thesis |
| dc_rights_str_mv | © 2022 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc (Physics))--University of Pretoria, 2023. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/90407 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:38:26.101Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/90407 Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer Mapasha, Refilwe Edwin u20780801@tuks.co.za Diale, Mantsae Kgalema, Sentserere Phodisho UCTD Li adsorption 2d anode materials DFT Li-ion batteris Graphane Dissertation (MSc (Physics))--University of Pretoria, 2023. Density functional theory calculations were performed to enhance interaction of Li/Na atoms with a graphane monolayer for LIBs and NIBs. The energetic stability, electronic and electrochemical properties of Li/Na atoms on a pristine graphane monolayer as well as on a graphane monolayer with H vacancies (VH) following a Line pathway and zigzag pathway were evaluated. Firstly, different Li adsorption sites and Na adsorption sites on a large supercell of 5×5×1 pristine graphane monolayer were considered, to establish the most energetically favourable site, based on binding energy calculations. All the adsorption sites of Li/Na atom on pristine graphane are energetically unfavourable (endothermic reaction). This is an indication that Li/Na atoms interacts weakly with graphane monolayer and could result with formation of unwanted Li/Na clusters. As a strategy to improve Li/Na atom interaction with graphane monolayer, a H vacancy (VH) was created. Different Li/Na adsorption sites at the vicinity of H vacancy were considered to establish the most energetically favourable site. All the Li/Na configurations relaxes towards the VH site. The Li/Na binding energies are higher than the cohesive energies of metallic bulk counterparts suggesting that clustering will not be reached easily. An increase in H vacancies along the line pathway from one VH1(L)to five VH5(L) leaves behind localized electrons ready to interact with the Li/Na atom resulting in high binding energies. The creation of H vacancies along the zigzag pathway from one VH1(Z) to ten VH10(Z) leavesbehind the dangling electrons on the nearest neighbour C atoms that pair and repel Li/Na atom away, yielding undesired low binding energies which become a setback for LIBs and NIBs. On the density of states analysis, adsorption of Li/Na atoms introduced new electronic states crossing the Fermi level. An observed transition from insulator to metallic behaviour will enhance the electron transmission in the graphane monolayer during battery operations. Li/Na storage capacities plots indicate that an increase of the Li/Na content result in an increase in the storage capacities. The average voltage obtained for the adsorption of five Li/Na atoms is 1.55 V/1.04 V. At this concentration, undesired clustering is unexpected until the voltages approaches zero. This implies that more adsorption of Li/Na atoms can still be considered to achieve a maximum concentration. NITheCS Physics MSc (Physics) Unrestricted 2023-04-20T10:49:47Z 2023-04-20T10:49:47Z 2023-09 2023 Dissertation * S2023 http://hdl.handle.net/2263/90407 en © 2022 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Li adsorption 2d anode materials DFT Li-ion batteris Graphane Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer |
| title | Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer |
| title_full | Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer |
| title_fullStr | Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer |
| title_full_unstemmed | Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer |
| title_short | Computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer |
| title_sort | computational insights of hydrogen vacancies mediating interaction of lithium and sodium adatoms with an electrode graphane monolayer |
| topic | UCTD Li adsorption 2d anode materials DFT Li-ion batteris Graphane |
| url | http://hdl.handle.net/2263/90407 |