Batteries with high energy density and satisfactory cycling stability are needed for reaching the targeted climate goals. Besides all-solid-state batteries, metal–oxygen and metal–sulfur batteries with liquid electrolytes (LEs) are a promising technology, possibly enabling a sustainable future. To increase the attainable cycling stability, the applied anodes, cathodes, and electrolytes have to be perfectly matched to each other. Otherwise, degradation reactions and detrimental chemical cross-talk (like the polysulfide shuttle in Li–S batteries and interdiffusion of redox mediators in Li–O2 batteries) can significantly decrease the cycling stability.
A solid electrolyte (SE) can be employed as ion-selective membrane to prevent cross-talk and propagation of dendrites, significantly improving cyclability. However, charge transfer across the SE/LE interface is sluggish, not only caused by the charge-transfer overpotential but also by the formation of a solid/liquid electrolyte interphase (SLEI). This layer consisting of decomposition products increases the internal resistance considerably.
Herein, we report on the fabrication of NASICON-based SE membranes for application in hybrid next-generation batteries. Thereby, four-point impedance measurements reveal the resistance of the growing interphase between the SE and an LE, while surface analytical methods reveal much needed information about the composition of the interphase. Evaluating different combinations of LE and SE, we identify the crucial influence of the solvent on interphase resistance and composition. In addition, the formation mechanism of the interphase is investigated in situ.