دکتر علی اکبر حیدری

In recent years, extensive studies have been conducted on secondary lithium-ion (Li-ion) batteries for innumerable applications, including power source for the portable electronics, electric vehicle, and electric storage reservoir. It is well-known that Li-ion batteries are made up of four different components, i.e., anode, cathode, electrolyte and separator. Even though separators play no roles in the electrochemical reactions, they physically separate the anode and cathode to avoid electrical short circuits when the free flow of Li ions transfers through the liquid electrolyte. According to the above-given statements, a separator takes a key part in the safety and the power capability of Li-ion batteries. Unil today, various separators have been introduced, among which polyolefin membrane separators have proved to be the most promising separators for commercial Li-ion batteries, arising from their outstanding properties, e.g., electrochemical stability, good mechanical strength, cost-efficiency, and thermal shutdown properties. Nevertheless, these membrane separators have faced several key drawbacks for vehicular storage, including non-polarity, low surface energy and poor thermal stability. Accordingly, the aim of this study is to review the types of polyolefin microporous separators which are widely employed in Li-ion batteries and all the intricate approaches taken for their surface modification. Several approaches including grafting by different methods, mussel-inspired technique and functionalization by inorganic nanostructures have been widely utilized to overcome the above- problems. It has been proven in the literature that outstanding properties can be provided through mono- and multilayer polyolefin separators if they are modified by proper strategies and materials, by which stat-of-the-art Li-ion batteries can be introduced..

Nanofiltration (NF) is a very important technique in separation and purification of aqueous and non-aqueous mixtures in several applications, such as the retention of dyes from water, which is the largest application in this field. Nonetheless, it is still a key issue to enhance the rejection performance and improve the flux, the key factors for the performance of the final membrane. Accordingly, MIL-53(Al) nanoparticles were utilized in this research work because of their small pore sizes, significant hydrophilicity and outstanding water stability.

In this study, the synthesis of the MIL-53(Al) nanoparticles was conducted. Then, the preparation of polyethersulfone (PES)-MIL-53(Al) mixed matrix membranes was done through the VIPS-NIPS method, which is the vapor-induced phase inversion (VIPS) method coupled with non-solvent-induced phase inversion (NIPS) technique, in which the co-solvent of 1,4-dioxane was employed. Finally, the prepared nanoparticles and membranes were characterized using several techniques including attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), and contact angle analyses.

Different membrane compositions with various MIL-53(Al) contents were prepared so that a membrane with superior performance in dye rejection application and high flux can be achieved. The performance of the fabricated membranes was investigated for rejection of various dyes in aqueous solutions including Reactive Red (RR), Direct Yellow (DY), Methyl Green (MG), and Crystal Violet (CV), based on which a great separation performance (dye rejections of 99.8, 99.5, 99.2, 98.8 and 97.1 for RR, MG, DY, CV and MB, respectively) and an excellent water flux (4.8 L/m2.h.bar) were provided by the membrane containing 0.06 wt% MIL-53(Al)..