Electronic Polarization Induced Coordination Directs Crystal Facet Engineering for Cryogenic Rechargeable Li||Cl 2 Batteries

Controlling the crystallographic facet orientation of in situ deposited products in conversion‐type batteries remains a fundamental challenge, as conventional synthesis‐based strategies cannot be applied to phases that nucleate and grow electrochemically during cell operation. Here, taking rechargeable Li||Cl 2 batteries as a model system, we elucidate the complete AlCl 4 − ‐mediated catalytic cycle governing the LiCl‐to‐Cl 2 charging conversion and identify the intrinsic covalent rigidity of the Al─Cl bond as the rate‐determining factor. On this basis, we propose an electronic polarization induced coordination (EPIC) strategy in which an in situ‐assembled [AlCl 2 (BZA) 2 ] + coordination cation (BZA = benzamide) activates directional N─H···Cl hydrogen bonds that selectively weaken the Al─Cl bond and lower the catalytic energy barrier. This molecular‐level intervention simultaneously redirects LiCl crystal growth from passivating {100} cubes toward dispersed {111}‐faceted nanocrystals through adsorption‐induced surface‐energy inversion, and operando x‐ray diffraction identifies these nanocrystals as the preferentially cycled, highly reversible phase, establishing a complete causal chain from coordination chemistry through catalytic kinetics to crystal facet engineering via a single design element. Li||Cl 2 cells employing the EPIC electrolyte sustain over 2500 stable cycles at −40°C under 1 A g −1 , tolerate current densities up to 30 A g −1 , and deliver 6.06 Ah in a cylindrical cell (ER26500) at 25°C.