Confined Predesolvation in a Yolk-Shell Metal-Organic Framework Interphase Enables Reversible Lithium-Metal Anodes

Artificial interfaces for lithium-metal anodes typically regulate nucleation after Li+ desolvation, while the preceding solvation-to-interface transition remains poorly controlled. Herein, we show that a yolk-shell H-Fe3O4@ZIF-67 interphase can act as a confined predesolvation layer. The subnanometer apertures of ZIF-67 sterically constrain intact solvated Li+ complexes, forcing partial solvent removal before electron transfer takes place. Polar Fe-O/Co-N environments favor anion-derived solid electrolyte interphase (SEI) chemistry, while the internal void accommodates the deposited Li. These coupled effects lower the Li nucleation overpotential to 14.6 mV, decrease the apparent interfacial activation energy to 34.53 kJ mol-1, and increase the Li+ transference number to 0.60. Symmetric cells operate for over 2000 h. High-loading LiFePO4 full cells retain 132.6 mAh g-1 after 400 cycles at 1 C and deliver an average Coulombic efficiency of 99.88%. Confining predesolvation at the molecular scale thus provides an effective strategy for stabilizing reactive metal anodes.