BAR-ILAN INSTITUTE OF NANOTECHNOLOGY & ADVANCED MATERIALS | 2019 ANNUAL REPORT

Prof. Doron Aurbach Department of Chemistry Member of BINA, Nano-Clean-tech Center & Nano-Energy Center Research Areas • Li metal based, very high energy density rechargeable batteries. • Advanced Li ion batteries for electro- mobility. • Advance analytical techniques (in-situ observations). • Batteries for large energy storage (e.g. rechargeable Mg batteries). • Super-capacitors (very fast energy storage & conversion). • Water desalination by electrochemical means. Abstract Topic 1 What are the true horizons for Lithium-Ion Batteries that can promote and advance the electro-mobility revolution in the 21-st century? We develop the most energetic, high capacity cathodes for Li ion batteries, most suitable for use in electric vehicles. We focus on developments and modifications by cation (Al3+, Zr4+, Mo4+) and anion (F-) doping and surface coatings (Al2O3, AlF3, ZrO2) of materials for positive electrodes (cathodes) of two promising families of lithiated transition metals oxides: Li & Mn-rich xLi 2 MnO 3 ·(1−x) Li[Ni a Co b Mn c ]O 2 (x<1, a+b+c=1) and Ni-rich LiNi x Co y Mn 1- x-y O 2 (x ¤ 1) materials respectively. Our group has extensively worked on the above issues during the last 8 years, aiming at understanding: A. How does the surface modification of Li & Mn-rich compounds can change the activation process during charging? B. Capacity and voltage fading during cycling and stabilization mechanisms of the above important cathode materials. C. Intrinsic properties of Ni-rich materials, like poor electronic conductivity, thermodynamic instability in charged state etc. Advanced Li-Ion Batteries for Electro- Mobility: High Capacity Cathodes Abstract Topic 2 Advanced Li ion batteries for electro- mobility, emphasis on active separators & scavengers in the cells. Advanced Li-ion batteries need accelerated power and very long operational life along with high energy density in order to fulfill the criteria for electrochemical propulsion. Beside the power generating electrochemical reactions, various parasitic reactions control the kinetics of the cell operations. The major parasitic reaction is auto decomposition of LiPF6 electrolyte salt at elevated temperatures and voltages, which generates HF and Lewis acids. Acidic species promote other parasitic reactions and transition metal ions dissolution from positive active materials is the most detrimental out of them. Transition metal (TM) ions dissolution from positive electrodes, migration to and deposition on negative electrodes, followed by Mn- catalyzed reactions of the solvent and anions, with loss of electroactive Li+ ions, is major degradation (DMDCR) mechanism in LIBs. Several measures for mitigating the effect of manganese dissolution or its consequences were explored over the years. Unfortunately, no single mitigation measure has proven completely successfully so far, i.e., without negatively affecting other properties of the LIB such as energy density, internal resistance, etc. Herein, we proposed novel multifunctional separators that can trap TM ions and prevent their migration and deposition on the negative electrodes, scavenge acidic species and dispense Na+/Li+ ions all at the same time, with significant benefits for LIB performance: increased capacity retention during operation at room and above-ambient temperatures, robust solid- electrolyte interface, as well as reduced charge transfer and film resistances at electrode surfaces. Schematic diagram of chemically active separator functions: (1) Mnx+ trapping; (2) acid proton scavenging; (3) Li+ ion sourcing; (4) LiF precipitation. Abstract Topic 3 Rechargeable Li batteries with very high energy density with practical Li metal anodes, thanks to the development of ‘magic’ electrolyte solutions. High theoretical specific capacity (3860 mAh g−1) and low negative redox potential make lithiummetal an ideal anode for high-energy-density Li batteries. However, dendrite growth and side- reactions with the electrolyte solutions limit the cycle life of the batteries with Li metal anode and cause severe safety problems, hindering practical use of these anodes. Many efforts have been made to stabilize Li metal anodes, including modification of the Li surface by various mechanical, physical, and chemical techniques, increase of the effective Li-electrode surface by use of an anode matrix with a very large surface area, the use of solid electrolytes, the addition of selected cations (such as cesium or rubidium) which protect the Li surface from dendrite formation according to the self-healing electrostatic shield mechanism and the use of functional electrolyte additives for the in situ formation of a protective SEI. We demonstrated excellent cycling performance of Li metal anodes in EC-free FEC based organic carbonate electrolyte solutions, which were shown to be the most promising electrolyte solutions for high energy-density and high-voltage rechargeable Li batteries. Symmetric Li|Li cells exhibited an extremely long cycle life and a stable voltage profile for more than 1100 cycles at a current density up to 2 mA cm −2 and an areal capacity of 3.3 mAh cm −2 with a minimal amount of electrolyte solution (22 μl cm −2 ). An increase in areal capacity up to 6 mA h cm −2 does not affect 46