MOF@ Nanofiber Separators for Lithium-Ion Batteries

The separator plays a crucial role in determining the safety and performance of lithium-ion batteries (LIBs) by acting as a mediator between the cathode and anode, preventing electrical contact, and providing channels for ionic transport. Most commercially available LIB separators are polyolefin microporous separators. However, the low melting points of polyolefin separators limit their thermal stability, leading to potential safety issues. Therefore, new alternatives are essential for developing high-performance batteries. Nylon 6,6 is a promising candidate due to its high thermal stability, low cost, good mechanical strength, and high chemical stability. One effective method to further improve the performance of nylon 6,6 separators is to combine them with Metal–Organic Frameworks (MOFs), which offer a high surface area and tunable morphology. The high surface area and porous structure provided by MOFs can increase ion permeability and allow the electrolyte to move more efficiently, thus improving the battery's charge/discharge rates and enhancing its specific capacity. In this study, ZIF-8, a small-pore MOF composed of zinc ions coordinated with 2-methyl imidazolate ligands, was coated onto nylon 6,6 nanofibers and used as a separator in lithium-ion batteries. ZIF-8@nylon 6,6 separators exhibited superior electrochemical properties, with a highly porous structure (76% porosity), high electrolyte uptake (340%), and high ionic conductivity (3.6 mS cm⁻¹). Additionally, these separators showed stable cycling performance over 200 cycles and maintained a high specific capacity even at high C-rates. The results demonstrate that MOF coating on nylon 6,6 separators is a promising approach for designing high-performance lithium-ion batteries.