Micro–Nano Hierarchical Structure From In Situ Functionalized MOFs Enables High‐Performance High‐Voltage Electrolytes

ABSTRACT Ideal solid‐state electrolytes (SSEs) should simultaneously possess excellent ionic conductivity, mechanical strength, electrochemical stability, and cathode compatibility. Here, inspired by the hierarchical architecture of organisms like the lotus leaf, a micro–nano hierarchical composite electrolyte was fabricated via in situ growth of a bifunctional metal–organic framework (F&OH‐ZIF‐8) on a cellulose acetate (CA) substrate. The micro‐ and nano‐sized F&OH‐ZIF‐8 crystals have the same composition but exhibit different size‐dependent advantages. The micro‐sized crystals provide greater structural continuity and mechanical support, whereas the nano‐sized crystals offer more accessible polar sites and interfacial regions for Li + coordination and transport. Their cooperative integration suppresses dendrite penetration and stabilizes the electrode/electrolyte interphases while facilitating Li + transport. An outstanding SSE with a room‐temperature ionic conductivity of 2.9 × 10 −3 S cm −1 , a lithium‐ion transference number of 0.61, and a wide electrochemical stability window extending to 5.5 V was obtained by this strategy, resulting in Li||NCM811 full cells achieving a high‐capacity retention of 80.9% after 300 cycles at 1C under a high cut‐off voltage of 4.6 V. This strategy of transforming existing commercialized ordinary membrane materials into more valuable electrolyte membranes has extremely high practical significance.