On-demand: Understanding Surface Reactions of the Solid Electrolyte Interface via Advanced Characterization Techniques

Passivation interfacial layers define the energy storage limits for next-generation batteries. It is crucial to understand how the bonding in salts, electrolytes, and solid electrodes can be used to tailor ion transport and to understand how these correlate to the formation of interfacial passivation layers. One of the routes that we have explored is to design task-specific ionic liquids and lithium salts to form stable, ionically conducting solid electrolyte interphase (SEI) layers in a controlled fashion.

After understanding these formation mechanisms and their advantages and disadvantages, we have also endeavored to create optimal artificial SEI layers that mimic these naturally formed SEI layers. On solid electrolytes, stabilizing interfaces in all-solid-state batteries (ASSBs) is crucial for the development of high-energy-density ASSBs. A facile, non-invasive, electrochemical protocol is explored to improve the interfacial impedance and contact at the interface of the solid electrolyte and electrode.

One of the requirements for next-generation batteries is extreme fast charging. A consequence of fast charging is severe lithium plating with graphite as the anode. To mitigate the lithium plating issue, other anode materials are explored, such as Li₄Ti₅O₁₂ (LTO) and TiNb₂O₇ (TNO). We probe the question if LTO do or do not form an SEI layer, and  we evaluate TNO as an anode material for extreme fast-charge applications. We also study the coating of separators with ceramic for increased safety and performance.

In all these studies, we have probed the surface via XPS and, where possible, via operando small-angle neutron scattering. The surface of solid polymer electrolytes, that could be argued to be the intermediate solution to all-SSBs, have been investigated in terms of their thermal degradation via in situ thermal XPS. The question that arises is whether temperature or the X-ray radiation induces the degradation.

Watch this webinar to learn more about:

• Probing the SEI layer via operando small angle neutron scattering and using ex situ XPS as a complementary tool
• Evolution of the SEI via operando techniques
• How X-rays influence the degradation of solid polymer electrolytes