Ion-Sieving Calixarene Fillers Boost Li⁺ Transport in Quasi-Solid Electrolytes for High-Loading Lithium Metal...

Calixarenes (CAs), featuring unique cavity architectures and exceptional host-guest capabilities, provide an attractive molecular platform for tailoring ion coordination and transport behaviors in solid-state electrolytes (SSEs). Despite these structural advantages, their potential in SSEs has been rarely explored. Herein, we design a calix[6]arene-functionalized (C6A) polymer quasi-solid electrolyte (PECQSE) via in situ polymerization, in which a cross-linked matrix is formed between urethane-functionalized poly(ethylene oxide) (PEG-IEM) and ethoxylated trimethylolpropane triacrylate (ETPTA). The incorporation of C6A establishes a size-selective, interaction-dominated ion-regulation framework, in which bulky TFSI^- exhibit restricted mobility, while Li⁺ transport is facilitated along conduction pathways, resulting in Li⁺ transference number of 0.76. Meanwhile, hydrogen-bonding interactions between C6A phenolic hydroxyl groups and urethane segments suppress PEG crystallinity and promote LiTFSI dissociation. These interactions facilitate interfacial LiTFSI reduction and support the formation of a LiF/Li₂O-rich SEI, which guides uniform lithium deposition and suppresses dendrite growth. Consequently, Li|Li symmetric cells exhibit ultralong cycling stability exceeding 7000 h with low polarization and high-loading LiFePO₄|Li full cells retain 80.6% capacity after 700 cycles at 2 C. The assembled 1 Ah pouch cell delivers excellent safety and durability with 91.8% retention after 240 cycles, demonstrating an effective interfacial engineering strategy for next-generation lithium metal batteries.