Achieving 4.7 V graphite/NCM811 batteries through MIL-101(Al) mediated interphase stabilization

Abstract

High-voltage graphite/LiNi0.8Co0.1Mn0.1O2 (NCM811) lithium-ion batteries (LIBs) face critical challenges in cycling stability, primarily driven by unstable electrode/electrolyte interfaces. Herein, we develop a synergistic interphase regulation strategy via a MIL-101(Al)-functionalized polyethylene (PE) separator (PE@MIL-101(Al)) to address these issues. The high porosity and polar surface of MIL-101(Al) significantly improve electrolyte wettability and constructs continuous ion-conducting pathways for higher ionic conductivity. The unsaturated open metal sites of MIL-101(Al) can adsorb PF6- anions to enhance the Li+ transference number. More importantly, the ordered pore architecture homogenizes Li+ flux to prevent localized high current densities and the weakened P-F bonds of the adsorbed PF6- promote PF6- decomposition into LiF, synergistically forming a uniform, dense, LiF-rich cathode/electrolyte interphase that suppresses lattice distortion, transitional metal dissolution and microcrack propagation. Simultaneously, MIL-101(Al) scavenges trace HF from, releasing Al3+ to construct a robust interphase enriching Al-O species on graphite. Owing to these synergistic effects, graphite/NCM811 cells achieve exceptional cycling stability, retaining 73.9% after 1000 cycles at 4.6 V and 70% after 800 cycles at 4.7 V. Our work demonstrates precise interfacial engineering in high-voltage LIBs through MOF-functionalized separators, bridging material innovation with interface optimization to provide a scalable strategy for high energy batteries.