Advanced Operando Analysis of Diverse Interfaces for All Solid State Batteries

All-solid-state batteries (ASSBs) have gained significant attention for their potential to enable highly safe and durable batteries, which are key technologies for the success of energy storage systems and electronic devices. With the improved ionic conductivity and atmospheric stability of solid electrolytes (SEs), the bottleneck for the commercialization of ASSBs extends beyond SE materials alone. Research has primarily focused on individual materials, revealing various issues in the interactions between materials within ASSBs. These issues can be broadly categorized into reduced contact due to volume changes and the formation of unwanted new layers from side reactions.<br/> <br/>During the intercalation/deintercalation process of lithium between the anode and cathode active materials, volume changes occur. Solid-state materials in ASSBs may fail to fill the empty spaces created by these volume changes, reducing contact between materials. This reduction in interfacial contact increases the battery's internal resistance, thereby diminishing its capacity and efficiency.<br/> <br/>While materials developed through different research efforts may individually exhibit excellent performance, there has been limited research on their interactions when combined. If lithium does not move smoothly between materials or if the materials are highly reactive, a new layer can form at the interface. This newly formed layer lacks electronic and ionic conductivity, acting as a high resistance. Ultimately, these issues accumulate, significantly contributing to the degradation of cell performance. Therefore, understanding and addressing these mechanisms are crucial for improving cycle life and efficiency.<br/> <br/>To investigate the various phenomena occurring at the interface, we developed in-situ/operando analytical techniques capable of structural, imaging, evolved gas, chemical bonding, and pressure variation analysis. These techniques have enabled a comprehensive understanding of ASSBs. Our investigation into the interphase evolution at the electrode interface in all-solid-state batteries using sulfide or halide solid electrolytes will be discussed at the meeting.