Operando Investigation of Electrochemical Ca Plating

Calcium (Ca) batteries have the potential to serve as a future alternative to lithium (Li) batteries, offering the advantage of not relying on scarce materials. Beyond energy storage, the electrochemical deposition of Ca metal is a key step in essential chemical processes, such as ammonia electrosynthesis. However, metallic Ca (like Li) also reacts with the electrolyte, leading to the formation of surface films. In Li-based systems, such films, known as the solid electrolyte interphase (SEI), are essential for long-term stability because they protect against ongoing electrolyte decomposition. In contrast, for many of the electrolytes tested for Ca plating, these films passivate the electrode and hinder continuous deposition. To develop electrolytes capable of forming beneficial SEI layers, it is crucial to understand their composition, properties, and mechanisms of formation. Operando synchrotron experiments can give direct insight into these largely unexplored processes.