Search Results (4)

The electric vehicle and energy storage markets have grown rapidly in recent years. Thermal runaway caused by malfunctioning Li-ion batteries is an urgent issue with many causes (e.g., mechanical, electrical, and thermal abuse). The most common cause of thermal runaway is the formation of an internal short circuit because of damage to the separator. There has been significant effort to improve the design of separators, but to our knowledge, only inorganic nanoparticle coatings are used in commercial Li-ion batteries. Here, hybrid organic/inorganic coating layers are synthesized in a pilot-scale process that was developed from a crosslinkable polyamide-imide synthesis technique. The fabrication process is optimized to achieve reproducible hybrid organic/inorganic coating layers that are thin (≤4 μm), permeable (≤250 s/100 cc), and thermally stable beyond 150 °C. The hybrid coating layer is applied to mini-18650 Li-ion cells to show that the discharge capacity did not change at low discharge rates, and the retention capacity after 500 cycles was better than that of the reference cells used for comparison. This work demonstrates that a novel hybrid coating layer has the potential to improve the stability of commercial Li-ion batteries. Full article

We used molecular dynamics to investigate the stability of graphene oxide (GO) layers supported on three polymeric materials, namely a polyvinylidene fluoride (PVDF), a pristine and a crosslinked polyamide–imide (PAI and PAI-cr). The membrane configurations consisted of a few layers of GO nanosheets stacked over the specified polymeric supports and submerged in water. We monitored the position, the tilt angle, and the radial distribution function of the individual GO nanosheets in respect to the plane of the supports. We showed that the outermost GO nanosheets were more distorted than those attached directly on the supports. The greatest distortion was observed for the GO nanosheets of the PVDF-supported system. Next, we recorded the density profiles of the water molecules across the distance from the layers to the polymer and discussed the hydrogen bonds between water hydrogens and the oxygen atoms of the GO functional groups. Full article

Polyamide (PA) thin-film composite (TFC) membranes are commonly applied in reversed osmosis (RO) and nanofiltration (NF) applications due to their thin, dense top-layer, and high selectivity. Recently, the conventional organic phase (i.e., hexane) during interfacial polymerization (IP) was replaced by less toxic ionic liquids (ILs) which led to excellent membrane performances. As the high price of most ILs limits their up-scaling, the potential use of inexpensive Aliquat was investigated in this study. The thin-film composite (TFC) membranes were optimized to remove flavor compounds, i.e., ethyl acetate (EA) and isoamyl acetate (IA), from a fermentation broth. A multi-parameter optimization was set-up involving type of support, reaction time for IP, water content of Aliquat, and concentration of both monomers m-phenylenediamine (MPD) and trimesoylchloride (TMC). The membranes prepared using Aliquat showed similar fluxes as those prepared from a reference IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C₄mpyr][Tf₂N]) but with better EA and IA retentions, even better than for a commercial RO membrane (GEA type AF). Finally, the recently introduced epoxide-curing of Bisphenol A diglycidyl ether (BADGE) with 1,6-hexanediamine (HDA) was investigated using Aliquat as organic phase. It is the first time this type of IP was performed in combination with an IL as organic phase. The resulting membrane was used in the filtration of a 35 µM Rose Bengal (RB) in 20 wt% dimethylformamide/ water (DMF/H₂O) feed mixture. A well-crosslinked poly(β-alkanolamine) film was obtained with a > 97% retention. Full article

Electrospun nanofiber, showing large specific area and high porosity, has attracted much attention across various fields, especially in the field of air filtration. The small diameter contributes to the construction of filters with high-filtration efficiency for fine particulate matter (PM), however, along with an increase in air resistance. Herein, composited nanofiber aerogels (NAs), a truly three-dimensional (3D) derivative of the densely compacted electrospun mat, were constructed with the blocks of polytetrafluoroethylene–polyamideimide (PTFE–PAI) composite nanofiber and polyimide (PI) nanofiber. PI/PTFE–PAI NAs with hierarchically porous architecture and excellent mechanical properties have been obtained by thermally induced crosslink bonding. Results indicated that sintering at 400 °C for 30 min could complete the decomposition of polyethylene (PEO) and imidization of polyamic acid (PAA) into PI, as well as generate sufficient mechanical bonding between adjacent nanofibers in the NAs without extra additive. The well-prepared PI/PTFE–PAI NAs could withstand high temperature up to 500 °C. In addition, the filtration tests illustrated that the composite NAs had an excellent performance in PM filtration. More importantly, the filtration behavior could be adjusted to meet the requirements of various applications. The excellent thermal stability and high-filtration efficiency indicated its great potential in the field of high-temperature air filtration. Full article