Flexible PVDF-HFP, Nickel MOF-based Hybrid Membrane as an Efficient Electrolyte for Lithium-Ion Batteries

The present investigation demonstrates a highly stable composite polymer electrolyte (CPE) membrane (NiPF6), designed to enhance the performance of solid-state lithium-ion batteries. The new CPE membrane has been fabricated by the blending of Ni-BDC metal-organic framework (MOF) (BDC: 1,4-benzenedicarboxylate), lithium salt, and PVDF-HFP (poly (vinylidene fluoride-co-hexa fluoropropylene)). The XRD of the CPE membrane clearly shows the presence of 2D Ni-BDC MOF. The mechanical properties and flame test validate the robustness of the membrane. The detailed morphological study of the membrane shows the presence of a porous surface and a layered structure. The CPE membrane exhibits a high ionic conductivity i. e. 1.5×10⁻⁴ S/cm at room temperature, which has increased to 5.99×10⁻⁴ S/cm at 55 °C. Considering the high ionic conductivity of the CPE membrane it has been used as an electrolyte for Li-ion cells. The Li-ion cell fabricated using the Ni-BDC CPE membrane has achieved a discharge capacity of 169.52 mAh/g @ 0.1 C rate, with impressive capacity retention(97 %). The cell showed a 149 mAh/g discharge capacity @1 C with 85 % retention over 300 cycles. Further, it delivered a capacity of around 128.55 mAh/g @ 2 C with 81 % capacity retention at 200 cycles. This enhancement is attributed to the incorporation of 2D Ni-BDC MOF, which has a porous and layered structure that might significantly improve the Li-ion conduction path. Hence, the enhancement in ionic conductivity is self-explanatory. The stable Li-ion conduction path might be formed at a higher C rate, hence the retention capacity has been increased @2 C rate compared to 1 C. More significantly, this is a promising approach for advancing solid-state lithium-ion battery technology by using new composite polymer electrolytes with efficient performance at room temperature.