Electrodeposition Stability Landscape for Solid-Solid Interfaces.

As solid-state batteries (SSBs) with lithium (Li) metal anodes gain increasing traction as promising next-generation energy storage systems, a fundamental understanding of coupled electro-chemo-mechanical interactions is essential to design stable solid-solid interfaces. Notably, uneven electrodeposition at the Li metal/solid electrolyte (SE) interface arising from intrinsic electrochemical and mechanical heterogeneities remains a significant challenge. In this work, the thermodynamic origins of mechanics-coupled reaction kinetics at the Li/SE interface are investigated and its implications on electrodeposition stability are unveiled. It is established that the mechanics-driven energetic contribution to the free energy landscape of the Li deposition/dissolution redox reaction has a critical influence on the interface stability. The study presents the competing effects of mechanical and electrical overpotential on the reaction distribution, and demarcates the regimes under which stress interactions can be tailored to enable stable electrodeposition. It is revealed that different degrees of mechanics contribution to the forward (dissolution) and backward (deposition) reaction rates result in widely varying stability regimes, and the mechanics-coupled kinetics scenario exhibited by the Li/SE interface is shown to depend strongly on the thermodynamic and mechanical properties of the SE. This work highlights the importance of discerning the underpinning nature of electro-chemo-mechanical coupling toward achieving stable solid/solid interfaces in SSBs.

Solid Electrolyte-Cathode Interface Dictates Reaction Heterogeneity and Anode Stability.

Solid-state batteries (SSBs) employing a lithium metal anode are a promising candidate for next-generation energy storage systems, delivering higher power and energy densities. Interfacial instabilities due to non-uniform electrodeposition at the anode-solid electrolyte (SE) interface pose major constraints on the safety and endurance of SSBs. In this regard, non-uniform kinetic interactions at the anode-SE interface which are derived from cathode microstructural heterogeneity can have significant impact on anode stability. In this work, we present a comprehensive insight into microstructural heterogeneity-driven cathode-anode cross-talk and delineate the role of cathode architecture and SE separator design in dictating reaction heterogeneity at the anode-SE interface. We show that intrinsic and extrinsic parameters, such as cathode loading, separator thickness, particle morphologies of active material and SE, and temperature can have significant impact on reaction heterogeneity at the anode-SE interface and thus govern anode stability. Tradeoff between energy density and anode stability while achieving higher cathode loading and thinner SE separators is highlighted, and potential strategies to mitigate this problem are discussed. This work provides fundamental insights into cathode-anode cross-talk involving interfacial heterogeneities and enhancement in energy densities of SSBs via electrode engineering.