E-Thesis 330 views
Development of Sodium Solid-State Electrolytes for Solid-State batteries / ANNA MICHALAK
Swansea University Author: ANNA MICHALAK
DOI (Published version): 10.23889/SUThesis.69582
Abstract
Sodium-based batteries are emerging as one of the most promising alternatives in the realm of post-lithium electrochemical energy storage systems. The abundance and global availability of sodium make it both a sustainable and economically viable option for large-scale energy storage. However, the hi...
| Published: |
Swansea University, Wales, UK
2025
|
|---|---|
| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Munnangi, A. R. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa69582 |
| Abstract: |
Sodium-based batteries are emerging as one of the most promising alternatives in the realm of post-lithium electrochemical energy storage systems. The abundance and global availability of sodium make it both a sustainable and economically viable option for large-scale energy storage. However, the high reactivity of sodium with conventional organic liquid electrolytes raises significant safety concerns, limiting the applicability of traditional sodium-ion batteries.To address these challenges, solid-state sodium batteries (SSSBs) have gained considerable interest as a safer and more stable alternative. By replacing flammable liquid electrolytes with solid electrolytes, SSSBs offer enhanced thermal stability and improved compatibility with sodium metal anodes.The performance of SSSBs is critically dependent on the properties of solid electrolytes, which must exhibit high ionic conductivity along with chemical and electrochemical stability. Among the solid electrolyte candidates, oxide-based materials such as BASE and NASICON have been widely explored due to their promising properties. However, both materials suffer from certain drawbacks, driving continued research into alternative solid electrolytes. This thesis focuses on the development of sodium rare-earth silicates, Na5MSi4O12, where M = Y, Gd, Dy, Sm, a lesser-known family of oxide-based solid electrolytes that have shown high sodium conductivity (10-3 S cm-1 at RT) and favourable stability with sodium metal. One of the primary challenges in developing these materials is the synthesis of pure compounds, as secondary phases such as Na3MSi3O9 and Na9MSi6O18 can negatively impact their performance.The thesis begins by introducing the background and context of the work, followed by three key chapters. Chapter 4 details the development of an optimised two-step solid-state synthesis method for Na5GdSi4O12, one of the most promising sodium rare-earth silicates. The method successfully produces highly conductive Na5GdSi4O12. The resulting material exhibits excellent ionic conductivity (1.99 × 10⁻³ S cm⁻¹ at 30°C) and wide electrochemical stability (up to 8 V vs Na/Na⁺). Additionally, Na5GdSi4O12 forms clean and stable interfaces with sodium metal, making it a strong candidate for SSSB applications. Chapter 5 extends the synthesis approach to other sodium rare-earth silicates, including Na5YSi4O12, Na5DySi4O12,and Na5SmSi4O12. All synthesised materials exhibit good ionic conductivities and broad electrochemical stability. Symmetric cell tests reveal that Na5SmSi4O12 and Na5GdSi4O12, in particular, demonstrate superior resistance to dendrite formation, a critical factor in the longevity and safety of SSSBs. Chapter 6 explores alternative synthesis methods, such as melt-quenching, to produce the Na5MSi4O12 compounds. This method proved successful for generating high-purity compounds with satisfactory ionic conductivities. Additionally, molten salt synthesis was attempted for Na5GdSi4O12, though it resulted in lower performance compared to other synthesis techniques.In summary, this thesis contributes to the advancement of sodium rare-earth silicate solid electrolytes by advancing the understanding of synthesis and evaluating their electrochemical performance. The results offer insights and potential pathways for further optimizing these materials for future SSB applications. |
|---|---|
| Item Description: |
A selection of content is redacted or is partially redacted from this thesis to protect sensitive and personal information. |
| Keywords: |
Electrochemical Energy Storage, Solid-state electrolyte, Solid-state batteries |
| College: |
Faculty of Science and Engineering |
| Funders: |
EPSRC doctoral training grant |