Fabrication of flexible polymer-MOF composite electrolyte for solid-state lithium metal batteries with high rate performance

• A 3D polymer-MOF solid-state electrolyte is fabricated via coaxial electrospinning. • CPZ-SSE is thin yet possesses a high critical current density of 3.2 mAh cm −2 . • A high lithium utilization of 21.07 mAh cm −2 is achieved. • The coated MOF fillers in CPZ-SSE prevent the interfacial side reactions. • The Li||CPZ-SSE||LFP delivers 86.66% retention after 500 cycles at 2 C. The transition from conventional lithium ion batteries to high-performance solid-state lithium metal batteries faces key challenges, including the establishment of an efficient and stable ion transport network within solid-state electrolyte and the achievement of uniform lithium deposition during cycling. Herein, a flexible polymer-metal organic framework (MOF) composite solid-state electrolyte with a three-dimensional network was fabricated through coaxial electrospinning. Specifically, MOFs are uniformly dispersed on polyacrylonitrile (PAN) nanofibers, resulting in a high room-temperature ionic conductivity (1.29 × 10 −3 S cm −1 ) and lithium ion transference number (0.79) after in situ thermal polymerization. The ZIF-8 coated PAN nanofiber enhances the reduction-tolerance of PAN nanofiber membrane against lithium metal and the increased MOF loading improves the Young’s modulus of the composite electrolyte (1.31 GPa), thus preventing the formation and penetration of lithium dendrites. Consequently, the mechanically robust composite electrolyte exhibits superior rate capability in Li||Li symmetric cell and Li||LiNi 0.83 Co 0.11 Mn 0.06 O 2 cell, along with extended cycle life in Li||LiFePO 4 cell.