Supramolecular ligands enable efficient ion transport in solid-state lithium batteries

Slow Li⁺ transport and unstable solid-state electrolyte interphase (SEI) seriously hindered the development of PVDF-based composite solid electrolytes. This work proposes a supramolecular ligand intervention strategy using 18-crown-6 (18-C-6) as an additive. Coordination between large-pore crown ethers and Li⁺ promotes the dissociation of LiFSI and increases the concentration of free Li⁺, thereby improving ion transport with a high ionic conductivity and Li⁺ transference number. Moreover, this coordination homogenizes Li⁺ flux and suppresses side reactions and dendrite formation. As a result, the developed electrolyte siginificantly enhanced the cycling stability of Li||Li cells up to 800 h with a reduced overpotential. Besides, the Li||NCM811 cells delivered 84.2% capacity retention over 2500 cycles at 10 C, and even at a high cut-off voltage of 4.5 V at 5 C, the cells retained 72.5% after 780 cycles. Structural and interfacial characterizations confirm the formation of a dense, LiF/Li₃N-rich SEI layer, which enhances mechanical strength and ionic transport. This work provides a robust modification approach using supramolecular ligands toward high-performance solid-state lithium metal batteries.