A Dipole-Engineered Electrolyte Paradigm to Overcome Desolvation Barriers for Exceptional Ultralow-Temperature Energy Storage.

Abstract

Electrochemical energy storage (EES) devices often exhibit poor low-temperature performance due to high interfacial desolvation energy barriers. While conventional strategies targeting ion-dipole interactions have improved desolvation kinetics, they suffer from a fundamental trade-off with bulk-phase ion diffusion. Here, a dipole-engineered electrolyte paradigm is proposed to overcome desolvation barriers for enhanced ultralow-temperature energy storage. Following this new paradigm, a weakly-dipolar-interacting electrolyte (WDIE) is developed by regulating dipole-dipole interactions within ionic solvates between primary and co-solvents. Through comprehensive experimental characterization and theoretical analyses, the interplay between dipole-dipole interactions and solvation dynamics across both interfacial and bulk phases is elucidated. Specifically, WDIE transforms the ionic solvate from conventional double-layer to distinctive mono-layer with attenuated solvent coordination number, effectively lowering solvent residence time and desolvation energy barriers. Simultaneously, it promotes solvent cluster dissociation, disrupting cross-linked electrolyte networks and enhancing bulk ion diffusion. As a proof of concept, WDIE-based supercapacitors exhibit optimized ultralow temperature performance, which retain 97.15% capacity from 20 to -70 °C, surpassing moderately- and strongly-dipolar-interacting electrolytes and ranking among the best reported. Moreover, theoretical calculations further demonstrate the broad applicability of this strategy when ionic radius exceeds 3.84 Å. This work demonstrates a scalable dipole-engineered electrolyte paradigm to overcome low-temperature EES limitations.