63 electrolyte solution (22 μl cm−2). An increase in areal capacity up to 6 mA h cm−2 does not affect the shape of the voltage profile of the symmetric Li|Li cells. The use of FEC-based electrolyte solutions that we developed enabled to obtain stable cycling of Li|LiNi0.6Co0.2Mn0.2O2 (NCM 622) and Li|LiNiO2 cells with practical loading for hundreds of cycles with with electrodes’ areal capacity of > 3 mAh cm−2. We attribute the high performance of the Li anodes to the formation of a stable and efficient passivating surface films on the surface of the Li metal electrodes due to the unique surface chemistry of our ‘magic’ electrolyte solutions. 1. D. Aurbach et al. “Fluoroethylene Carbonate as an Important Component for the Formation of an Effective Solid Electrolyte Interphase on Anodes and Cathodes for Advanced Li-Ion Batteries” ACS Energy Lett.,2017, 2 (6), pp 1337–1345. 2. D. Aurbach et al. “Very Stable Lithium Metal Stripping–Plating at a High Rate and High Areal Capacity in Fluoroethylene Carbonate-Based Organic Electrolyte Solution” ACS Energy Lett., 2017, 2 (6), pp 1321–1326. Abstract Topic 4 Developing devices for large energy storage based on supercapacitors. Supercapacitors are very fast energy storage and conversion devices. The mechanism of supercapacitors is based on adsorption of ions at the Electric Double and high level of safety. However, many challenges must be addressed in order to develop a robust magnesium metal-based battery. The magnesium electrochemistry group focuses on two major aspects: 1. Development of magnesium cathode materials – one of the major challenges to realizing a complete rechargeable Mg battery is to develop a high voltage cathode material, which can reversibly store Mg cations with fast kinetics (fast charge and discharge rates). Most of the known inorganic intercalation materials suffers from low Mg ions mobility in their solid lattice. In our group we synthesize and characterizing new material for this purpose. 2. Electrolyte solutions R&D – Mg metal reacts rapidly when it comes in contact with almost all the polar aprotic solvents (carbonates, acetonitrile etc.), many of the conventional electrolyte (ClO4, BF4, SO3CF3 and AsF6) and with atmospheric components (water, CO2, O2 and N2). The product of these surface reactions is electronic and ionic insulating surface film, which block the electrochemical activity of the anode and the full cell. Our group, studies and develops new clusters of electrolyte solutions which enable reversible dissolution/deposition of magnesium and a wide electrochemical window. 1. 2. Figure 1: show the calculated energy density of different secondary battery systems. Figure2: show the gravimetric capacity of different candidate materials for rechargeable systems. Abstract Topic 5 Development of rechargeable magnesium batteries. Nowadays, lithium ion batteries are the most advanced commercially available energy storage technology. However, high cost and safety concern prevent such systems to be utilized for large energy storage. Magnesium metal exhibits desirable properties, which makes it as the natural choice as anode material for large energy storage batteries. These properties include: low reduction potential (-2.37 V vs NHE), high volumetric capacity (3,833 mAh cm–3), non-dendritic growth, low cost, Layer Capacitance (EDLC) that consists of only electro-static interactions rather than redox reactions. Relaying on that EDLC interactions, supercapacitors exhibit much higher power density than batteries (few thousands W/kg compare to tens W/kg), due to the fast kinetics of the electro-static interactions. The additional durable advantage of supercapacitors driven by the nature of EDLC phenomena is excellent cyclability. Since the structure of the electrodes does not change during charge and discharge, the life time of supercapacitor is nearly unlimited. On the other hand, the weak EDLC interactions in supercapacitors also leads to their main drawback which is low energy density. This limitation is strongly noticeable in aqueous electrolyte-based supercapacitors. In our lab we synthesize high capacity carbonaceous electrodes materials. We also develop positive electrodes based on MnO2 with aqueous electrolyte solutions. The main focus is on development of devices for large energy storage (load leveling & grid applications). Lithium-ion batteries Supercapacitors Anode/ Cathode materials LiCoO2 or LiMnO2/ Graphite Active Carbon/ Active Carbon Chargedischarge cycles Up to 3000 Over 10000 Power density (W/kg) low high Energy density (mAh/g) high low Charging Time hours Minutes Work process The charging and discharging of the energy is slow, and with time the chemical components are decomposing The energy is exchanged electrostatically on the materials surface. There are no side reactions. Thereby these devices are very stable
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