Conductivity enhancement within garnet‐rich polymer composite electrolytes via the addition of succinonitrile

All‐solid‐state lithium‐ion batteries (ASSLIBs) are promising alternatives to conventional organic electrolyte‐based batteries due to their higher safety and higher energy densities. Despite advantages, ASSLIBs suffer from issues like high charge transfer resistances due to the brittleness of the inorganic solid electrolyte and chemical instabilities at the lithium/electrolyte interface. Within this work, we investigate composite electrolytes (CEs) based on garnet‐type Li₆.₄La₃Zr₁.₄Ta₀.₆O₁₂ (LLZTO), polyethylene oxide, and lithium bis(trifluoromethanesulfonyl)imide, prepared via a solvent‐free cryo‐milling approach in contrast to conventional solvent‐mediated synthesis. Compositions ranging from polymer‐rich to garnet‐rich systems are investigated via X‐ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy in order to determine the compatibility of the cryo‐milling process toward membrane fabrication along with the possible chemical interactions between the composite membrane components. Electrochemical impedance spectroscopy is used to study the role of ceramic to polymer weight fraction on ionic conductivity. It is shown that the addition of succinonitrile (SCN) to the garnet‐rich CEs can significantly improve the ionic conductivity compared to the SCN‐free CEs.