Meta-state electrolytes with quasi-ordered clusters for stable lithium metal batteries

Abstract

Ionic aggregation state in liquid electrolytes is generally constrained by the salt solubility limit of the solvent matrix, restricting the accessible coordination structures and limiting opportunities for electrolyte engineering. Here, we report a class of meta-state electrolytes (MSEs) that transcend this conventional solubility limit and access an atypical aggregation regime. Enabled by external-field regulation coupled with nonequilibrium kinetic access, the MSE reshapes the Li⁺ coordination landscape and stabilizes a previously inaccessible meta-state domain beyond the threshold region of the ternary phase diagram. Within this regime, the MSE remains macroscopically homogeneous while forming large anion-rich clusters with local coordination environments resembling those of solid lithium salt, yielding an inorganic-rich solid electrolyte interphase (SEI) with high mechanical robustness and fast Li+ transport. Accordingly, the MSE effectively suppresses interfacial parasitic reactions, enabling Cu||LiNi0.5Co0.2Mn0.3O2 pouch cells to retain 70% of their capacity after 136 cycles at 45°C. Our study establishes external-field regulation of the Li+ coordination environment as a new design principle for advanced electrolytes, with broad implications for solid/liquid interfacial chemistry.