Investigating the Influence of the Effective Ionic Transport on the Electrochemical Performance of Si/C-Argyrodite Solid‐State Composites

Solid-state batteries have the potential to outperform conventional lithium-ion batteries, as they offer higher energy densities, necessary for the increasing demand for portable energy storage. Silicon-graphite composites are considered to be one of the most promising alternatives to the lithium metal anode due to their low lithiation potential and resistance against dendrite formation. Since these composites show insufficient ionic conductivity, a fast-conducting solid electrolyte is needed to facilitate the charge carrier transport. Optimizing the volume fractions of the solid electrolyte is crucial to ensure sufficient charge carrier transport and achieve the optimal performance. In this work, the influence of the charge carrier transport in a silicon on graphite (Si/C)/argyrodite solid electrolyte composite on the electrochemical performance is studied. By systematically varying the ratio of the Si/C to solid electrolyte, it was found that the effective ionic conductivity of the electrode composite improves exponentially with increasing content of the solid electrolyte, which in turn leads to an increase in the specific capacity of the composite across all C-rates. This study highlights the importance of understanding and customizing charge carrier transport properties in solid-state anode composites to achieve optimum electrochemical performance

Visualizing the Chemical Incompatibility of Halide and Sulfide‐Based Electrolytes in Solid‐State Batteries

Halide-based solid electrolytes are currently growing in interest in solid-state batteries due to their high electrochemical stability window compared to sulfide electrolytes. However, often a bilayer separator of a sulfide and a halide is used and it is unclear why such setup is necessary, besides the instability of the halides against lithium metal. It is shown that an electrolyte bilayer improves the capacity retention as it suppresses interfacial resistance growth monitored by impedance spectroscopy. By using in-depth analytical characterization of buried interphases by time-of-flight secondary ion mass spectrometry and focused ion beam scanning electron microscopy analyses, an indium-sulfide rich region is detected at the halide and sulfide contact area, visualizing the chemical incompatibility of these two electrolytes. The results highlight the need to consider more than just the electrochemical stability of electrolyte materials, showing that chemical compatibility of all components may be paramount when using halide-based solid electrolytes in solid-state batteries

Exploring Aliovalent Substitutions in the Lithium Halide Superionic Conductor Li_{3– x}In_{1– x}Zr_xCl₆ (0 ≤ x ≤ 0.5)

In recent years, ternary halides Li3MX6 (M = Y, Er, In; X = Cl, Br, I) have garnered attention assolid electrolytes due to their wide electrochemical stability window and favorable roomtemperatureconductivities. In this material class, the influences of iso- or aliovalentsubstitutions are so far rarely studied in-depth, despite this being a common tool for correlatingstructure and transport properties. In this work, we investigate the impact of Zr substitution onthe structure and ionic conductivity of Li3InCl6 (Li3-xIn1-xZrxCl6 with 0 ≤ x ≤ 0.5) using acombination of neutron diffraction, nuclear magnetic resonance and impedance spectroscopy.Analysis of high-resolution diffraction data shows the presence of an additional tetrahedrallycoordinated lithium position together with cation site-disorder, both of which have not beenreported previously for Li3InCl6. This Li+ position and cation disorder lead to the formation ofa three-dimensional lithium ion diffusion channel, instead of the expected two-dimensionaldiffusion. Upon Zr4+ substitution, the structure exhibits non-uniform volume changes alongwith an increasing number of vacancies, all of which lead to an increasing ionic conductivity inthis series of solid solution

Exploring Aliovalent Substitutions in the Lithium Halide Superionic Conductor Li3-xIn1-xZrxCl6 (0 ≤ X ≤ 0.5)

In recent years, ternary halides Li3MX6 (M = Y, Er, In; X = Cl, Br, I) have garnered attention as solid electrolytes due to their wide electrochemical stability window and favorable room-temperature conductivities. In this material class, the influences of iso- or aliovalent substitutions are so far rarely studied in-depth, despite this being a common tool for correlating structure and transport properties. In this work, we investigate the impact of Zr substitution on the structure and ionic conductivity of Li3InCl6 (Li3-xIn1-xZrxCl6 with 0 ≤ x ≤ 0.5) using a combination of neutron diffraction, nuclear magnetic resonance and impedance spectroscopy. Analysis of high-resolution diffraction data shows the presence of an additional tetrahedrally coordinated lithium position together with cation site-disorder, both of which have not been reported previously for Li3InCl6. This Li+ position and cation disorder lead to the formation of a three-dimensional lithium ion diffusion channel, instead of the expected two-dimensional diffusion. Upon Zr4+ substitution, the structure exhibits non-uniform volume changes along with an increasing number of vacancies, all of which lead to an increasing ionic conductivity in this series of solid solutions.</p