3D interconnected MOF-derived asymmetric bilayer solid-state electrolyte for enabling homogeneous Li deposition of all-solid-state lithium metal batteries

Although it has enhanced safety and high energy density, all-solid-state lithium metal battery (ASSLB) still faces challenges in achieving high ionic conductivity, uniform Li⁺ flux, good interfacial compatibility, and enough mechanical strength in solid-state electrolytes (SSEs). In this work, we synthesized a composite solid electrolyte featuring an asymmetric bilayer structure (designated as 3MP-PSE) based on a crosslinked network of MOFs. The as-formed 3MP-PSE had high mechanical strength (16.8 MPa), satisfactory ionic conductivity (0.63 mS cm⁻¹), high Li⁺ transference number (0.64), and broad potential window (5.0 V). This unique solid electrolyte enabled uniform Li deposition to ensure good interfacial compatibility with lithium metal electrodes, as evidenced by XPS analysis, which effectively suppressed the growth of lithium dendrites. The Li–Li symmetric battery using the 3MP-PSE was proven to be stable over 400 h at a current density of 0.1 mA cm⁻². Moreover, the Li//3MP-PSE//LiFePO4 battery exhibited impressive electrochemical performance at room temperature, with a high reversible specific capacity of 159.6 mAh g⁻¹, a capacity retention of 82.7%, and an average Coulombic efficiency (CE) of 99.87% after 200 cycles at 0.2 C, demonstrating highly stable cycling performance of the battery.