Functional PBI membrane based on polyimide covalent organic framework for durable lithium metal battery

The development of multifunctional separators with excellent safety and electrochemical performance benchmarks has always been a prevalent issue for the overall efficiency of lithium metal battery (LMB). In this study, polyimide covalent organic framework (PI-COF) and polybenzimidazole (PBI) are used to fabricate bifunctional membranes. PBI is used as the membrane matrix material due to its remarkable thermal properties, while the microstructure and polar functional groups of the COF regulate Li⁺ flow and prevent the growth of Li dendrites. As expected, the Li/PBI@PI-COF/Li symmetric cell displays stable cycling with low ion diffusion activation energy and quick lithium-ion transport kinetics, effectively inhibiting dendrite formation and enhancing the stability of Li⁺ plating/stripping. Additionally, the LiFePO₄/Li cell with PBI@PI-COF membrane delivers exceptional cycling discharge capacity and coloumbic efficiency of 99.9 % after 100 cycles at 1C. It also has good capacity retention and excellent cycle stability as a result of the strong solid electrolyte interphase (SEI) film formed by the introduction of COF. Thus, this research may lead to new avenues to develop new functional porous membrane for high-performance LMBs.