Multihydrogen-bond-bridged composite solid electrolytes enabling continuous Li ⁺ pathways for stable solid-state lithium batteries

Composite solid electrolytes (CSEs) hold great promise for advancing safer and higher-energy-density solid-state batteries. However, the poor interface compatibility caused by the lithium carbonate (Li ₂ CO ₃ ) passivation layer on the garnet-type Li _6.4 La ₃ Zr _1.7 Ta _0.3 O ₁₂ (LLZTO) surface leads to an inhomogeneous distribution of ceramic particles and discontinuous lithium ion (Li ⁺ ) transport, especially for high-content ceramics. Herein, we chemically convert the Li ₂ CO ₃ layer into brushlike poly(ethylene glycol) methyl ether acrylate- co -2-(3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido)ethyl methacrylate (PEGMA- co -UPyMA) polymers. These modified ceramics (LLZTO- g -PEGMA- co -UPyMA) are integrated with a dynamic supramolecular ionic conducting polymer (DSICP) through hydrogen bond coupling, yielding a homogeneous LLZTO- g -PEGMA- co -UPyMA@DSICP CSE with continuous Li ⁺ transport pathways, even at 90 weight % ceramic loading. This CSE enables exceptional cycling stability, with Li|LiFePO ₄ cells retaining 88.8% capacity after 2000 cycles and 4.4-volt Li|NMC811 cells maintaining 83.7% after 300 cycles. Impressively, the 1.26–ampere hour pouch cell retains 85.6% capacity after 100 cycles, demonstrating unprecedented feasibility for practical solid-state lithium batteries.