Anode interfaces in all-solid-state batteries

Thesis

Solid-state batteries have the potential to transform the transportation industry but there are substantial hurdles to overcome before fully realising their benefits. This thesis primarily addresses the challenges associated with Li-free or so called anodeless solid-state cells. One of the most significant issues is the morphological instability observed at the interface between the metal anode and solid electrolyte during charging and discharging, which leads to cell shorting.

Chapter 3 describes investigation of the use of a silver metal interlayer in Li-free all-solid- state batteries. The chapter focusses on the cycling performance with a sulphide solid electrolyte and employs techniques such as PEIS, SEM/EDX, PFIB and XPS. These techniques help to understand the role of the silver metal interlayer during charge and discharge, thereby mitigating contact loss. Moreover, the interfacial reactivity between the lithiated silver and the sulphide solid electrolyte reveals the presence of interfacial by-products.

Chapter 4 investigates the mechanisms underpinning the operation of a graphite-silver composite interlayer in a Li-free solid-state setup using various techniques such as operando XRD, SEM/EDX and electrochemical lithiation. The investigation reveals the structural changes occurring in the composite interlayer at different rates of charge and discharge. The critical current density with the composite interlayer was determined to be 2 mA cm-2 and strategies to improve it are explored. Additionally, the role of silver nanoparticles in the composite interlayer is discussed.

Finally, Chapter 5 explores plasma cleaning as a surface treatment technique to remove impurities from the air exposed surface of Na-β”-Alumina (NBA) solid electrolyte. Optimising conditions for the plasma treatment results in a relatively low interfacial resistance of NBA against a Na metal anode at room temperature. SEM and XPS techniques provide insight on the effects of plasma cleaning.

Authors: Agarwal, V

• DOI: 10.5287/ora-m8vj9rgbn
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English