eprintid: 10185647
rev_number: 11
eprint_status: archive
userid: 699
dir: disk0/10/18/56/47
datestamp: 2024-02-29 16:14:19
lastmod: 2024-02-29 16:14:19
status_changed: 2024-02-29 16:14:19
type: thesis
metadata_visibility: show
sword_depositor: 699
creators_name: Wei, Runzhe
title: Materials design of potassium-ion pre-intercalated cathodes for sodium-ion batteries
ispublished: unpub
divisions: UCL
divisions: B04
divisions: C06
divisions: F56
note: Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
abstract: Lithium-ion battery (LIB) is currently the most popular energy storage form from mobile devices to large-scale grids because of its high energy density, long cycle life, low maintenance and versatile. However, due to the increasing demand and cost, limited resources and environmental concerns, it is essential to explore the feasibility of new battery technologies, which can potentially reduce the pressure of LIB or even replace it in the future. Among various choices, sodium-ion battery (SIB) is regarded as one of the most promising candidates due to its low cost and abundance. More importantly, as another member of alkali metal, Na has similar characteristics as Li does, which leads to much transferable knowledge.
Since SIB is still at early stage, many challenges, especially for cathode materials, need to be overcome, because of the larger ion size and higher standard redox potential. This project offers some solutions and insights by applying K+ pre-intercalated cathode materials for SIB, which is different from the mainstream research of SIB cathodes. The focus of the project is to investigate the role of K+ in the process of ion intercalation and diffusion. The first work is applying potassium iron hexacyanoferrate (K-FeHCF Prussian blue with a tunnel structure) as cathode for SIB. Compared to Na+, K+ can better fit in the Prussian blue structure, resulting in better structural stability. Additionally, the lower standard reduction potential of K over Na leads to a higher cell voltage. The K+ pre-intercalated KFeHCF makes it a hybrid-ion battery system when being used in a SIB cell. Introducing a level of [Fe(CN)6]4- vacancy can regulate the intercalation mechanism, therefore maximize the enhancement provided by K+ pre-intercalation. The second work is using potassium vanadyl phosphate (KVOPO4 with a layered structure) as cathode for SIB. Benefiting from the even larger size of K+ over Na+, the presence of K+ in the interlayer space of KVOPO4 acts as a “pillar” to provide extra space for Na-ion intercalation in KVOPO4. KVOPO4 exhibits robust Na kinetics and improved structural stability, resulting in a higher cycling capacity and better rate capability compared to NaVOPO4. Finally, full cell test is carried out to further verify the two designs described above, where hard carbon is used as the anode electrode. The roles of K+ remain in the full cell and both cathode materials exhibit comparable performance to half cell test. This indicates the feasibility of K+ pre-intercalated cathode materials in SIB cells and both materials can be even more promising in the future by optimizing the designs.
date: 2024-01-28
date_type: published
oa_status: green
full_text_type: other
thesis_class: doctoral_open
thesis_award: Ph.D
language: eng
primo: open
primo_central: open_green
verified: verified_manual
elements_id: 2139976
lyricists_name: Wei, Runzhe
lyricists_id: RWEIX11
actors_name: Wei, Runzhe
actors_id: RWEIX11
actors_role: owner
full_text_status: public
pagerange: 1-241
pages: 241
institution: UCL (University College London)
department: Chemistry
thesis_type: Doctoral
citation:        Wei, Runzhe;      (2024)    Materials design of potassium-ion pre-intercalated cathodes for sodium-ion batteries.                   Doctoral thesis  (Ph.D), UCL (University College London).     Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/10185647/2/Thesis%20final%20Runzhe%20Wei.pdf