(Invited) Strategies for Enhancing the Stability of the Electrode-Electrolyte Interphase in Sulfide-Based Solid-State Batteries

Abstract

In recent years, all solid-state batteries (SSBs) have gained significant attention as the next-generation energy storage device due to their high energy density, improved safety, and enhanced stability. Sulfide-based solid electrolytes (SEs) have garnered significant attention among various inorganic materials for their exceptional properties, including high ionic conductivity and robust mechanical properties. These features make them promising candidates for SSBs, ensuring both manufacturability and long-term cycle life. For example, Li-argyrodites (e.g., Li6PS5X, and X = Cl, Br, I) and Na-thioantimonate (e.g., Na2.88Sb0.88W0.12S4) offer high ionic conductivities (> 10-3 S/cm) that are comparable to those of liquid electrolytes. However, its practical application is still under-achieved due to a few technical challenges. Among the various issues, our focus is on the electrode-electrolyte interphase, which degrades the cycle life of the SSBs.At the cathode-electrolyte interphase, narrow electrochemical window (1.71 V – 2.01 V) of Li6PS5X unwantedly prompt the oxidative decomposition of solid-electrolyte. At the anode-electrolyte interphase, Li-argyrodite SEs can be easily reduced by Li metal or oxidized by cathode active materials because of its narrow electrochemical window (1.71 V – 2.01 V). The resulting byproducts at electrode-electrolyte interphases can unwantedly lead to capacity fading and an increase in cell resistance. Additionally, SSBs made with the Li-argyrodite SEs suffer from Li-dendrite penetration during repeated cycles and consequent internal short circuits.To address these challenges, we propose strategies for passivating the interphases between the cathode and the solid electrolyte, as well as between the metallic anode and the electrolyte in solid-state batteries (SSBs). Through a combinatorial study, we aim to elucidate the extent and severity of interfacial side reactions in solid-state batteries (SSBs). In addition, the optimal coating strategies of LiNbO3 for cathodes and Li3N coating on metallic Li anode will be discussed. The optimized Li3N as an artificial solid electrolyte interphase (SEI) layer on the metallic Li anode enables more than 5000 cycles without failure in symmetrical cells.Furthermore, we will also highlight a strategy for passivating the electrode-electrolyte interphases of Na-based solid-state batteries (SSBs) that employ thioantimoniate as the electrolyte material. The approaches to passivate the cathode and metallic Na anode will be presented. Comprehensive electrochemical and spectroscopic studies will be conducted to identify the source of degradation and elucidate the improvement mechanisms associated with each strategy.