Modification of separator by glassy metal-organic framework with isotropic and grain-boundary-free characteristics enables reversible lithium plating/stripping in lithium metal batteries

The issue of lithium dendrite growth of lithium metal anodes (LMAs) significantly impedes the practical application of lithium metal batteries (LMBs). In this study, we propose a glassy MOF, namely gZIF-62, as a highly appealing candidate for the modification of commercial polypropylene (PP) separator. The gZIF-62/PP composite separator can exhibit improved thermal stability and electrolyte wettability, induce homogeneous lithium ion flux as well as uniform lithium metal nucleation and growth, decrease the lithium nucleation overpotential and increase the lithium ion transference number, leading to smooth and dense surface morphology of lithium deposits and reversible lithium plating/stripping behaviors of LMAs. With the employment of gZIF-62/PP separator, the Li|Cu half cells can run stably with a high average coulombic efficiency of 92.76% during 120 cycles, while the Li|Li symmetric cells could maintain a relatively small and stable voltage polarization of about 27.3 mV without short-circuit case for 950 h cycling, at a current density of 0.5 mA cm -2 with a capacity of 0.5 mAh cm -2 . Moreover, the Li|LFP full cell with a LFP loading of about 2.0 mg cm -2 exhibits an enhanced cycling performance with a capacity retention of 74.42% and an average CE of 99.84% during 1000 cycles at 1 C. In addition, the gZIF-62/PP separator based cell presents better rate capability than the crystalline-ZIF-62(cZIF-62)/PP separator based cell. The boosted electrochemical performance of LMBs with the use of gZIF-62/PP separator can be attributed to the intrinsic characteristics in terms of isotropy and lack of grain boundaries belonging to the gZIF-62 material. • Glassy ZIF-62-coated PP separator enables stable lithium metal deposition. • The isotropic and grain-boundary-free nature of gZIF-62 homogenizes Li⁺ flux. • Symmetric cells wih gZIF-62/PP separator achieve long-term cycling stability.