Solid-state batteries (SSBs) have been proposed as promising alternatives to conventional Li-ion batteries because of their high level of safety and power density. However, solid electrolytes (SEs) that possess high ionic conductivity and electrochemical stability are still in need. Also, problems arisen at the electrolyte│electrode interface, such as the space charge layer (SCL) formation, phase and mechanical instability, are yet to be addressed. To overcome these obstacles, one needs comprehensive knowledge on the physics and electrochemistry of the SSB system, which can be provided from both continuum and atomistic perspective.

This thesis is divided into two parts. In the first part, a comprehensive continuum model is constructed for simulating the electro-chemo-mechanical...[ Read more ]

Solid-state batteries (SSBs) have been proposed as promising alternatives to conventional Li-ion batteries because of their high level of safety and power density. However, solid electrolytes (SEs) that possess high ionic conductivity and electrochemical stability are still in need. Also, problems arisen at the electrolyte│electrode interface, such as the space charge layer (SCL) formation, phase and mechanical instability, are yet to be addressed. To overcome these obstacles, one needs comprehensive knowledge on the physics and electrochemistry of the SSB system, which can be provided from both continuum and atomistic perspective.

This thesis is divided into two parts. In the first part, a comprehensive continuum model is constructed for simulating the electro-chemo-mechanical (ECM) response of an SSB. The model resolves the bulk transportation of charged species and their interfacial transfer kinetics. It also studies the formation of SCLs at interfaces and the development of interfacial stresses. The results suggest that the SCLs and the charge transfer kinetics are intertwined. The emergence of the SCLs and the depletion of reactants increases the charge transfer overpotential. We also studied the coupling between electrochemistry and mechanics at interfaces. The results indicate that the strong electric fields originating at interfaces yield significant stresses. Our result, thereby, highlight the necessity of considering the ECM coupling in the SCLs when modeling an SSB.

In the second part of this thesis, density functional theory (DFT) is utilized to study the physical characteristics of two SE candidates, namely the sodium antiperovskite, Na₃OCl , and the lithium halide, Li₃YX₆, where X = I, Br, Cl and F. We conducted ab-initio calculation to study the physical properties of Na₃OCl such as the formation energies of various defects, the defect transport behaviour, and the effect of substituting alkali earth metals into the sodium site. Similarly, we studied the phase stability, electrochemical stability, anti-site defect formation energies and Li transportation of various Li₃YX₆. Based on the result, we discussed the impact of anion and transition metal substitution to physical characteristics of Li₃YX₆. The second part of this thesis thus provide a theoretical foundation for further improving Na₃OCl and Li₃YX₆ as potential SE materials for SSBs.