All-impurities Scavenging, Safe Separators with Functional Metal-Organic-Frameworks for High-Energy-Density Li-Ion Battery

Li-ion batteries (LIBs) have wide applications owing to their high-energy density and stable cycle characteristics. Nevertheless, with the rapid expansion of electric vehicle market, issues such as explosion of LIBs and the need to secure a longer driving distance have emerged. In this work, functional metal-organic frameworks (MOFs) are introduced as a separator in LIBs, in which a highly heat-resistant polymer separator is fabricated through electrospinning. The MOFs can scavenge impurities (including gas, water, and hydrofluoric acid) that positively affect battery performance and safety. The multi-functional separator suppresses salt decomposition when a nickel-rich cathode is operated at high voltage and high temperature through it. This delays the deterioration of the cathode interface and results in a superb cycle stability with 75% retention even in the presence of 500 ppm of water in the electrolytes. In addition, the pouch cell is manufactured by enlarging the separator, and the degree of electrode swelling due to gas generation and interface degradation in the pouch state is alleviated to 50% or less. These findings highlight the necessity of scavenging impurities to maintain excellent performance and provides the development direction of functional separators in LIBs

A Dry Room-Free High-Energy Density Lithium-ion Batteries Enabled by Impurity Scavenging Separator Membrane

Although lithium-ion batteries (LIBs) are used in various fields, such as small devices and electric vehicles, the low cycling stability due to the acceleration of salt degradation at high temperatures remains a significant challenge. The batteries are typically assembled in a dry room that controls moisture because lithium salts in the electrolytes are highly reactive with moisture, which has a significant effect on the battery performance. In this work, impurity scavenging separator membrane (ISM) was fabricated using a powerful H2O and HF scavenging material. This material was synthesized by an urethane reaction between porous silica (p-SiO2) and (3-isocynatopropyl)triethoxysilane (ICPTES). The p-SiO2 reaction with ICPTES suppressed the acidification of the electrolyte with water and resulted in maintaining the shape of the SiO2 particles. The multifunctional separator exhibited high capacity retention of 87%, 79%, and 74% at various electrodes including LiMn2O4 (LMO)//Li4Ti5O12(LTO), Li[Ni0.8Co0.1Mn0.1]O-2 (NCM)//graphite, and LMO//graphite, respectively, at high temperature (55 degrees C). Furthermore, the ISM improves the cycle stability of batteries that use an electrolyte containing 1000 ppm of water. For the first time, a pouch full-cell was manufactured in a dry room-free system to confirm the excellent H2O and HF scavenging ability of the developed ISM, which was confirmed by the large area of battery size (4x6 cm(2)). This method presents a new approach for cost reduction in the electric vehicle marke