Lithium metal batteries (LMBs) offer exceptional energy density and output voltage. However, their practical application remains hindered by sluggish ion transport and uncontrolled lithium dendrite formation, particularly under fast-charging conditions. Here, we report a facet-engineered anion-regulating separator based on zeolitic imidazolate framework-8 (ZIF-8) with preferentially crystal-exposed (110) facets. The coordinatively unsaturated Zn centers on this surface serve as Lewis acid sites that selectively anchor bis(trifluoromethanesulfonyl)imide anions (TFSI-), inducing directional Li+ flux and suppressing dendritic growth. Concurrently, the microporous framework facilitates spatial lithium confinement, mitigating local current density and enhancing interfacial stability. As a result, the engineered separator enables ultra-stable cycling of Li||Cu cells for over 1400 cycles at 2 mA cm-2 and 1 mAh cm-2, delivering an average Coulombic efficiency of 98.7%. In full-cell configurations, LiFePO4 (LFP) cells exhibit 99.9% Coulombic efficiency over 3000 cycles at 5 C, while high-loading Li||LiNi0.8Co0.1Mn0.1O2 (NCM811, 12.30 mg cm-2) cell retains 84.4% of its capacity after 135 cycles. Furthermore, a Li||LFP pouch cell with a high cathode loading of 19.92 mg cm-2 demonstrates robust cycling over 170 cycles. These findings establish facet-engineered separators based on framework materials as a versatile and scalable strategy for advancing stable and fast-charging metal batteries.
Liu et al. (Mon,) studied this question.