Operando soft X‐ray microscope study of rechargeable Zn–air battery anodes in deep eutectic solvent electrolyte

Abstract

Zn–air batteries are very promising devices for energy storage at high energy density due to their intrinsic safety, environmental friendliness, and low cost, but still, there are key issues to be solved to get to the industrial scale. One of the unsolved problems is the poor cyclability of batteries based on aqueous solvents that urges to consider nonaqueous solvents. Among different possible options are deep eutectic solvents, which are cost‐effective and technologically relatively easy to implement. The present investigation reports for the first time an operando scanning soft X‐ray microscope analysis of the Zn behaviour in a choline–chloride/urea deep eutectic solvents electrolyte during the cathodic and anodic phase formation processes taking place in battery charge and discharge, providing a platform for in‐depth space–time dependent investigations of the chemistry of crystallites evolving during potential cycling. These operando measurements have been enabled by the construction of a novel wet cell, improving the design and filling protocol of earlier generation cells developed by authors.High‐resolution soft X‐ray microscope images were acquired in two modes: (a) dynamic mode at a fixed beam energy, allowing to follow morphology evolution under electrochemical control and (b) static mode for selected morphologies representative of characteristic Zn growth and dissolution steps.