Erbium(III) chloride (ErCl3) is a premier rare-earth metal halide precursor used to synthesize high-voltage, high-conductivity halide solid-state electrolytes (SSEs), such as lithium erbium chloride (Li3ErCl6) and multi-anion variations like Li3ErCl(6-x}Brx. Similar to YCl3, the trivalent erbium ion (Er}^{3+}) coordinates with six chloride ions to assemble an edge-sharing ErCl6]^{3-} octahedral sub-lattice. This framework features highly disordered lithium-ion sites and a low-barrier 3D conduction pathway, enabling excellent room-temperature ionic conductivity (~1.4 * 10^{-3} S cm-1) and a broad electrochemical stability window exceeding 4.5 V vs. Li/Li+.

Mechanochemical Ball Milling (Dry Processing): This is the standard laboratory protocol to achieve close atomic mixing and force the mechanochemical reaction prior to final crystallization. (1) Stoichiometric Batching: Inside an Argon-filled glovebox (H2O, O2 < 0.1 ppm), weigh out anhydrous LiCl and anhydrous ErCl3 in a strict 3:1 molar ratio:

                                         

Notes: (1) Please store the ErCl3 powder in a dry place (glovebox is preferred due to its air/humidity sensitivity).

References: 

1. Q. Shao, et al. New Insights into the Effects of Zr Substitution and Carbon Additive on Li3–xEr1–xZrxCl6 Halide Solid Electrolytes, ACS Appl. Mater. Interfaces 2022, 14, 6, 8095–8105
2. J. S. Kim, et al. Universal Oxychlorination Strategy in Halide Solid Electrolytes for All-Solid-State Batteries, Adv. Energy Mater., 2026, DOI: 10.1002/aenm.202506744