Dipole-mediated interfacial solvation for efficient Li-ion transport in dendrite-free Li metal batteries

Abstract

Efficient Li⁺ transport is crucial for ensuring the stability of Li metal anodes in Li metal batteries (LMBs). However, conventional vehicular transport in non-aqueous electrolytes, where Li⁺ migrates with an intact solvation shell, results in sluggish ion transport kinetics, thereby exaggerating Li⁺ flux heterogeneity and promoting dendritic deposition. Here, we propose a dipole-mediated solid–liquid interfacial solvation regulation strategy that leverages the abundant interface provided by a nano-ceramic electrolyte coating on the separator to accelerate and homogenize the Li⁺ transport. The high-dipole molecule 2,5-difluoro-4-nitrobenzoic acid (DNA) was employed to functionalize the ceramic coating, inducing strong ion–dipole interactions with Li⁺ and lowering the transport energy barrier at the interfacial region. Its low LUMO level further enables preferential reduction to generate a Li₃N/LiF-enriched interphase, stabilizing the Li surface and suppressing electrolyte decomposition. As a result, the dipole-regulated interface delivers a high ionic conductivity (0.517 mS cm⁻¹, compared with the pristine separator at 0.308 mS cm⁻¹) and a Li⁺ transference number of 0.646, enabling dendrite-free Li deposition. Li‖LiFePO₄ and Li‖NMC811 full cells exhibit markedly improved long-term cycling stability under high areal-capacity loadings, demonstrating the effectiveness and practical viability of this dipole-mediated interfacial solvation strategy for enhancing ion transport in LMBs.