Enhancing safety and electrochemical performance of lithium-ion batteries with P/N-IL@NH2-UIO-66 functionalized PVDF separators

The development of high-performance separator materials has become crucial with the ever-increasing demands for enhanced safety and energy density of lithium-ion batteries in electric vehicles and large-scale energy storage systems. Here, a novel high-safety functionalized separator was prepared by synthesizing a composite material that encapsulates phosphorus‑nitrogen-containing ionic liquid (P/N-IL) within NH₂-UIO-66-Zr metal-organic framework (MOF), and then combining this composite with a polyvinylidene fluoride (PVDF) P/N-IL@NH₂-UIO-66/PVDF separator. This functionalized P/N-IL@NH₂-UIO-66/PVDF separator significantly improves the flame-retardant performance of NCM811 batteries, effectively mitigating the risks of electrolyte combustion and explosion. Meanwhile, the porous structure of P/N-IL@NH₂-UIO-66 material optimizes the Li⁺ transport pathways, resulting in an increase in the ionic conductivity of NCM811 battery o 3.1 × 10⁻⁴ S/cm (compared to only 3.4 × 10⁻⁶ S/cm for the pure PVDF separator). The Li⁺ transference number is also elevated to 0.68. Moreover, after 600 cycles at a 1C current density, the capacity retention rate reaches as high as 71 %, with an average coulombic efficiency of 96 %, substantially enhancing the electrochemical performance and cycling stability of the battery. This work offers a novel technological pathway for the development of high-safety, high-performance lithium-ion batteries, as well as for the application of ionic liquids and MOFs.