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

Abstract

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 (Li₂CO₃) passivation layer on the garnet-type Li_6.4La₃Zr_1.7Ta_0.3O₁₂ (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 Li₂CO₃ 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|LiFePO₄ 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.