Electronic Polarization Induced Coordination Directs Crystal Facet Engineering for Cryogenic Rechargeable Li||Cl₂ 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||Cl₂ batteries as a model system, we elucidate the complete AlCl₄ ^--mediated catalytic cycle governing the LiCl-to-Cl₂ 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 [AlCl₂(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||Cl₂ 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.