Mesoscale Physics of Electrified Interfaces with Metal Electrodes
Li-ion batteries (LIBs) are currently pervasive across portable electronics and electric vehicles and are on the ascent for large-scale applications such as grid storage. However, commercial LIBs based on intercalation chemistries are inching toward their theoretical energy density limits. Consequently, the rapidly growing demands of energy storage have necessitated a recent renaissance in exploring battery systems beyond Li-ion chemistry. Next-generation batteries that utilize Li metal as the anode can improve the energy density and power density of LIBs. Despite the theoretical promise, the commercialization of metal-based batteries requires overcoming several hurdles, stemming from the unstable nature of Li in liquid electrolytes. Upon repeated charging, the metal anode undergoes unrestricted growth of dendrites, devolving to a thermal runaway in extreme circumstances. By replacing the organic liquid electrolyte with a non-flammable solid electrolyte, solid-state batteries (SSBs) can potentially provide enhanced safety attributes over liquid electrolyte cells. Upon pairing of solid electrolytes with a Li metal anode, such systems present the unique possibility of engineering batteries with high energy density and fast charging rates. However, there are a number of technical challenges and fundamental scientific advances necessary for SSBs to achieve reliable electrochemical performance. The formation of dendritic morphologies during charging and the loss of active area at the anode-electrolyte interface during discharging are two critical limitations that need to be addressed.
In this thesis, the morphological stability of the Li metal anode is examined based on the mechanistic interaction of electrochemical reaction, ionic transport and surface self-diffusion, that is further dependent on aspects including the thermal field and electrolyte composition. The origin of electrochemical-mechanical instability and metal penetration due to heterogeneities in solid-state electrolytes such as grain boundaries will be analyzed. The phenomenon of contact loss at solid-solid interfaces due to the competing interaction between electrochemical dissolution and Li mechanics will be studied. Lastly, the mechanistic attributes governing the thermal stability of solid-solid interfaces in solid-state batteries will be examined. Overall, the dissertation will focus on understanding the fundamental mechanisms underlying the evolution of solid-liquid and solid-solid interfaces in energy storage and derive potential design guidelines toward achieving stable morphologies in metal-based batteries.
- Doctor of Philosophy
- Mechanical Engineering
- West Lafayette