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

The development of poly(vinylidene fluoride)-based composite solid-state electrolytes is severely hindered by slow Li⁺ transport and unstable solid-state electrolyte interphases. This study addresses these challenges by proposing a supramolecular ligand intervention strategy using 18-crown-6 as an additive. Coordination between the large-pore crown ethers and Li⁺ promotes lithium bis(fluorosulfonyl)imide dissociation and increases the free Li⁺ concentration, thereby enhancing ion transport with a high ionic conductivity and an improved Li⁺ transference number. Moreover, this coordination homogenizes the Li⁺ flux, suppressing side reactions and dendrite formation. Consequently, the modified electrolyte significantly enhances the cycling stability of Li||Li cells up to 800 h with a reduced overpotential. Additionally, the Li||NCM811 cells delivered 84.2% capacity retention after 2500 cycles at 10C, and retained 72.5% capacity after 780 cycles even at a high cut-off voltage of 4.5 V at 5C. Structural and interfacial characterizations confirmed the formation of a dense LiF/Li₃N-rich SEI layer, which enhances mechanical strength and ionic transport. This study provides a robust modification approach using supramolecular ligands to achieve high-performance solid-state lithium-metal batteries.