Fabrication Of Metal Organic Frameworks-based Mixed Matrix Membranes And Their Applications In Li-S Battery

Metal organic frameworks（MOFs）,preparing from organic linkers and inorganic secondary building units（SBUs）with large specific surface area,high porosity,ordered porous structure and tunable structures have received wide attention.Thus,MOFs have been intensively investigated in various applications like gas/liquid separation,catalysts,sensing and energy storage,etc.However,as a class of porous crystalline materials,their inherent crystalline and fragile nature have largely limited the industrial processes.To solve it,mixing MOFs and polymers to fabricate MOFs based mixed matrix membranes（MMMs）that can combine the good processability of polymer membranes to conquer the inherent nature of MOFs.However,pre-synthesis of MOFs is a tedious work and there are still some inevitable problems like the dispersity of MOFs particles,the compatibility between MOFs and polymers and the percentage of remained porosity,etc.Therefore,it is particularly important to develop a method that can efficient fabrication with high production efficiency for MOF-based MMMs will provide solid basis for the potential industrialization process of MOFs.These key problems have led us to devote ourselves to the development of simple preparation methods for mixed matrix membranes based on metal-organic frameworks.Therefore,two methods for the rapid preparation of MOF-based mixed matrix membranes and device were designed.And the performance of the modified separator in in lithium-sulfur battery was also studied.The specific research work is as follows:1.A facile in-situ heat-assisted solvent-evaporation method to facilely fabricate porous and robust MOF-based MMMs in industrial-level efficiency with oven-heating or microwave-assist has been reported（fabrication time,5 min）.Fourier transform infrared spectroscopy（FT-IR）,X-ray powder diffraction（XRD）,and scanning electron microscopy（SEM）were used to character the structure,elemental composition and morphology of the prepared materials.In addition,this method can be used to fabricate MMMs with different MOFs（including Zr-MOFs,etc.）and universality of polymers were also explored.The obtained MMMs have accessible pores and excellent robustness.2.MOF-based MMMs can serve as powerful coatings to decorate commercial PP fabricated through that in-situ heat-assisted solvent-evaporation method.The prepared materials were characterized by FT-IR,XRD and SEM.The electrochemical performance and rate performance of the battery were studied by cyclic voltammetry（CV）,electrochemical impedance spectroscopy（EIS）method and constant current charge and discharge method.Li-S battery based on this kind of separator has higher initial capacity(1163.7 m A h g^-1,0.5 C),capacity retentionand rate performance than commercial PP.The average specific capacity fade rate is 0.08%every turn after 700cycles of charge and discharge.The powerful method that can facilely and massively produce MOF-based porous MMMs applicable in battery separator application might largely facilitate the industrialization process of MOFs.3.A photo-induced heat-assisted processing method that can enables shaping of MOFs into diverse devices（e.g.,fiber,hollow tube,Janus hollow tube and double-layer/triple-layer membrane,etc.）has been proposed.This simple method combine photo-induced shaping and heat-assisted solidification in a protocol,which combining the advantages of photo-polymerization polymer and MOFs together,they possess excellent robustness,flexibility,compatibility and self-healing properties.4.A kind of MOF-based triple-layer separator with stepped channels has been readily fabricated through the photo-induced multi-dimensional fabrication of MOFs.It exhibits boosted specific capacity(1365.0 m Ah g^-1)and cycling performance(0.03%fading per cycle from 100^th to 700^th cycle),superior to single-layer/double-layer separators and commercial PP.This work demonstrates the concept of rational construction of triple-layer structured separators for boosted Li-S performance and provide a novel point for the applications of MOF-based devices in energy storage.Considering the diversity of MOFs species with various pore sizes and channels,the discovery of integrated combinations of MOFs hosts for multi-functional targets is expected.