Owing to high ionic conductivity and good oxidation stability, halide‐based solid electrolytes regain interest for application in solid‐state batteries. While stability at the cathode interface seems to be given, the stability against the lithium metal anode has not been explored yet. Herein, the formation of a reaction layer between Li3InCl6 (Li3YCl6) and lithium is studied by sputter deposition of lithium metal and subsequent in situ X‐ray photoelectron spectroscopy as well as by impedance spectroscopy. The interface is thermodynamically unstable and results in a continuously growing interphase resistance. Additionally, the interface between Li3InCl6 and Li6PS5Cl is characterized by impedance spectroscopy to discern whether a combined use as cathode electrolyte and separator electrolyte, respectively, might enable long‐term stable and low impedance operation. In fact, oxidation stable halide‐based lithium superionic conductors cannot be used against Li, but may be promising candidates as cathode electrolytes.

With growing interest in solution‐based processing of electrolytes for all‐solid‐state batteries comes the need to more deeply understand potential detrimental effects of the solvent on electrolyte materials, as well as effects on the cell performance that may not have been evident by structural characterization alone. Herein, the superionic solid electrolyte Li6PS5Cl is treated with five organic solvents selected for a range of different physical and chemical properties. The electrolytes treated with solvents that do not lead to obvious degradation are used in cathode composites of solid‐state batteries In/LiIn│Li6PS5Cl│NCM‐622:Li6PS5Cl. After treatment in some solvents, the solid electrolyte remains seemingly unaffected, but a strong influence on the solid‐state battery performance is observed, revealing underlying effects that warrant deeper study.

Solid‐state batteries with a lithium metal anode (LMA) are promising candidates for the next generation of energy storage systems with high energy and power density. However, successful implementation of the LMA requires deeper insight into the lithium metal–solid electrolyte (Li|SE) interface. Since lithium is highly reactive, reaction products form when it comes into contact with most solid electrolytes (SEs) and the resulting interphase can have detrimental effects on cell performance. To better understand the formation of interphases, Li|SE interfaces are studied with time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS), which provides chemical information with high sensitivity in 2D as well as 3D and is a valuable complement to commonly used techniques. To investigate the interphase, lithium is deposited in situ on SE pellets either through lithium vapor deposition or electrochemical lithium plating. Subsequent depth profiling provides information about the stability of the Li|SE interface and about the microstructure of the formed interphase. At the Li|Li6PS5Cl interface of lithium metal with argyrodite‐type Li6PS5Cl, an apparently covering Li2S‐rich layer is found as major part of the interphase. Independent of the deposition method, a combination of ToF‐SIMS and atomic force microscopy indicates a thickness of about 250 nm for the Li2S‐rich interlayer.

Owing to high ionic conductivity and good oxidation stability, halide‐based solid electrolytes regain interest for application in solid‐state batteries. While stability at the cathode interface seems to be given, the stability against the lithium metal anode has not been explored yet. Herein, the formation of a reaction layer between Li3InCl6 (Li3YCl6) and lithium is studied by sputter deposition of lithium metal and subsequent in situ X‐ray photoelectron spectroscopy as well as by impedance spectroscopy. The interface is thermodynamically unstable and results in a continuously growing interphase resistance. Additionally, the interface between Li3InCl6 and Li6PS5Cl is characterized by impedance spectroscopy to discern whether a combined use as cathode electrolyte and separator electrolyte, respectively, might enable long‐term stable and low impedance operation. In fact, oxidation stable halide‐based lithium superionic conductors cannot be used against Li, but may be promising candidates as cathode electrolytes.

Herein, three electrolyte families (liquid, polymer, and ceramic) are compared and their future perspectives in research and application are discussed. First, the transport mechanism for each family is presented, as their beneficial and taxing properties stem from the differences in these mechanisms. Following a discussion of each group, their advantages, and limitations, a clear conclusion can be drawn on the need to focus on research on solid electrolytes, which present brighter prospects in terms of significant future advances in lithium‐based battery systems. Yet, in a more realistic perspective based on current work by companies such as Samsung, Solid Power, and QuantumScape, it is our understanding that the hybridization of polymer and solid electrolytes will likely dominate practical electrolyte chemistries, at least in the near future, given that the synergetic properties of the two families are larger than their single parts. Inevitably, solid‐state electrolytes will dominate, mainly in electric vehicles and future lithium battery chemistries.

Magnesium batteries are promising candidates for post-lithium energy storage systems due to their low cost, high volumetric energy density, and low risk of dendrite formation. This study reports a new magnesium ion conducting ionogel electrolyte based on a Metal-Organic Framework (MOF) structure (UiO-66) impregnated with an ionic liquid, magnesium bis[(trifluoromethyl)sulfonyl]imide in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide. Comparably high conductivity of 5.7 × 10 À 5 S cm À 1 can be achieved at room temperature. By employing the prepared MOF-ionogel electrolyte, a reversible quasi-solid-state magnesium battery (QSSMB) is reported. Surface analysis unveils the possible origin of the large overpotential of magnesium plating and stripping. The findings suggest that MOF-based materials are a promising class of ionogel electrolyte templates for QSSMBs. The results on the magnesium anode will be useful to define optimization strategies for magnesium metal anodes in SSMBs.

Thiophosphate solid electrolytes containing metalloid ions such as silicon or germanium show a very high lithium-ion conductivity and the potential to enable solid-state batteries (SSBs). While the lithium metal anode (LMA) is necessary to achieve specific energies competitive with liquid lithium-ion batteries (LIBs), it is also well known that most of the metalloid ions used in promising thiophosphate solid electrolytes are reduced in contact with an LMA. This reduction reaction and its products formed at the solid electrolyte|LMA interface can compromise the performance of an SSB due to impedance growth. To study the reduction of these metalloid ions and their impact more closely, we used the recently synthesized Li7SiPS8 as a member of the tetragonal Li10GeP2S12 (LGPS) family. Stripping/plating experiments and the temporal evolution of the impedance of symmetric Li|Li7SiPS8|Li transference cells show a severe increase in cell resistance. We characterize the reduction of Li7SiPS8 after lithium deposition with in situ X-ray photoelectron spectroscopy, time-of-flight secondary-ion mass spectrometry, and solid-state nuclear magnetic resonance spectroscopy. The results indicate a continuous reaction without the formation of elemental silicon. For elucidating the reaction pathways, density functional theory calculations are conducted followed by ab initio molecular dynamics simulations to study the interface evolution at finite temperature. The resulting electronic density of states confirms that no elemental silicon is formed during the decomposition. Our study reveals that Li7SiPS8 cannot be used in direct contact with the LMA, even though it is a promising candidate as both a separator and a catholyte material in SSBs.

We report the immobilization of 4-dimethylaminopyridine (DMAP), a versatile organocatalyst for sterically demanding esterifications, on mesoporous silica particles and macromesoporous silica monoliths, both possessing optimized properties for continuous flow synthesis. An alkyne-functionalized DMAP derivative was immobilized via click chemistry; the materials were characterized by physisorption analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and elemental analysis. While silica particles were functionalized in batch and packed into a packed-bed reactor, monoliths were cladded with a polyether ether ketone (PEEK) tube after sol-gel synthesis and functionalized in a circulating flow process. Samples with three different catalyst loadings were prepared, in order to study the impact of the catalyst amount on the mesopore space as well as the catalytic performance. In continuous flow experiments, complete conversion of 1-phenylethanol to phenylethylacetate was achieved with both materials and short contact times. Monoliths exhibited far lower pressures than packed bed reactors (7 bar at a flow rate of 1 mL min À 1 ) and reached turnover rates up to 9.3x10 À 2 s À 1 , which is almost twice as high as a comparable batch experiment. The absence of diffusion limitations in monoliths made investigations on reaction kinetics with microkinetics-dominated experiments possible. This study demonstrates that all properties needed for a successful transfer of immobilized organocatalysts to sophisticated flow syntheses with complex organocatalysts can be met with functionalized meso-macroporous monoliths.