Nitro functionalization and nanoscale confinement enable ether-based quasi-solid electrolytes with stable lithium metal and high-voltage compatibility

Abstract

Quasi-solid-state electrolytes (QSSEs) that simultaneously enable fast Li⁺ transport, stable lithium metal interfaces, and high-voltage compatibility remain a critical challenge for lithium metal batteries. Herein, a synergistic strategy combining functional modification and nanoscale confinement is proposed by integrating nitro-functionalized UiO-66 (UiO-66-NO₂) with an ether-based electrolyte (1 M LiTFSI in DME) to construct a MOF-based QSSE, denoted as UNP@D-LE. The electron-withdrawing NO₂ groups reduce the electron density of ZrO₈ clusters, enhancing anion anchoring and stabilizing ether oxygen, while the confined MOF micropores induce a compact solvation structure dominated by aggregated TFSI⁻ solvates and DME–TFSI⁻ coordination, as revealed by Raman spectroscopy. As a result, UNP@D-LE exhibits a high ionic conductivity of 3.98 × 10⁻³ S cm⁻¹, a Li⁺ transference number of 0.61, and an expanded oxidative stability window exceeding 5.0 V versus Li⁺/Li. The electrolyte enables stable Li plating and stripping for over 2000 h at 0.2 mA cm⁻² and delivers an enhanced critical current density of 2.2 mA cm⁻². When paired with a high-voltage NCM811 cathode, quasi-solid-state Li‖NCM811 cells deliver 73.3% capacity retention after 100 cycles at 0.5 C over 3.0–4.3 V, and 72.4% retention after 50 cycles at 0.1 C over 3.0–4.4 V. This work highlights the effectiveness of combining functionalized MOFs and ether electrolytes for high-performance QSSE design.