Editors’ Choice—Review—Designing Defects and Diffusion through Substitutions in Metal Halide Solid Electrolytes

Abstract

Ternary metal halides A 3 MX 6, (A = Li+, Na+; M = trivalent metal; X = halide) are a promising family of solid electrolytes for potential applications in all-solid-state batteries. Recent research efforts have demonstrated that chemical substitution at all three sites is an effective strategy to controlling battery-relevant material properties. The A 3 MX 6 family exhibits a wide breadth of structure and anion sublattice types, making it worthwhile to comprehend how chemical substitutions manifest desirable functional properties including ion transport, electrochemical stability, and environmental tolerance. Yet, a cohesive understanding of the materials design principles for these substitutions have not yet been developed. Here, we bring together prior literature focused on chemical substitutions in the A 3 MX 6 ternary metal halide solid electrolytes. Using materials chemistry perspectives and principles, we aim to provide insights into the relationships between crystal structure, choice of substituting ions and the extent of substitutions, ionic conductivity, and electrochemical stability. We further present targeted approaches to future substitution studies to enable transformative advances in A 3 MX 6 solid electrolytes and all-solid-state batteries.

Enabling a Co-Free, High-Voltage LiNi0.5Mn1.5O4 Cathode in All-Solid-State Batteries with a Halide Electrolyte

“…Contrary to sulfide-based SSEs, the halide-based SSEs have been recently popularized in cathode composites because of their higher oxidation stability limit compared to their sulfide counterparts. ,− Asano et al were the first to report that low-crystalline Li 3 YCl 6 (LYC) and Li 3 YBr 6 halide SSEs had ionic conductivities of 0.51 and 0.72 mS cm –1 . Various types of other halide SSEs that contain other transition metal ions such as In, Zr, and Sc have been discovered and found to exhibit suitable ionic conductivities with higher oxidative stability windows, thus enabling stable cycling performance of a >4 V class of cathode materials, including NCM cathodes without the protective coating layers. − However, experimental analysis of their decomposition and its products beyond the oxidation stability window as well as their application and performance limitations when used with higher-voltage (>4.8 V) cathode systems have yet to be explored. In this study, we first introduced LYC as the representative halide SSE in the LNMO cathode composite and compared the chemical compatibility between LNMO and LPSCl/LYC via electrochemical, spectroscopic, and electron microscopy methods.…”

Progress in Sodium Silicates for All‐Solid‐State Sodium Batteries—a Review

“…The advantage of these electrolytes is their good cyclability when combined with high‐voltage cathodes. [ 48–50 ]…”

“…The advantage of these electrolytes is their good cyclability when combined with high-voltage cathodes. [48][49][50] Rare-earth silicates are a new class of solid-state materials that contain octahedra and tetrahedra frameworks and 3D structures compared to NASICON. In the Na 2 O-R 2 O 3 -SiO 2 system (R = Sc, Y, and other rare earths), Na 5 RSi 4 O 12 (N5-type) materials are the less explored for ionic conduction.…”

Synthesis and Calculations of Wurtzite Al1–xGdxN Heterostructural Alloys

“…Isostructural alloyssolid solutions of two or more materials with the same underlying crystal structureare the most common types of functional alloys. Isostructural alloys as electronic materials have applications in photovoltaics (e.g., II–VI materials such as CdSe x Te 1– x and III–V-based multijunction technologies), energy storage (e.g., Li 6 PS 5– x Se x (Cl,I), Li 3 Y 1– x In x Cl 3 ), − and thermoelectrics (e.g., PbSe x Te 1– x ), etc. Heterostructural alloys, in contrast, form between materials with different structures, such as alloys between wurtzite AlN and rocksalt ScN, wurtzite ZnO and rocksalt MnO, and orthorhombic SnS and rocksalt CaS .…”