Danny Gelman

Aluminum–air battery based on an ionic liquid electrolyte

Metal–air batteries, and particularly aluminum–air (Al–air) batteries, draw a major research interest nowadays due to their high theoretical energy content of Al (gravimetric and volumetric). Nevertheless, the implementation of Al–air batteries as a sustainable energy storage device is hampered by severe hurdles. Al anode high corrosion rate in aqueous alkaline solution is of major concern in terms of Al usage and safety. In non-aqueous electrolytes adverse Al surface activation substantially limits any power output. This study presents a novel non-aqueous Al–air battery. This battery utilizes 1-ethyl-3-methylimidazolium oligo-fluoro-hydrogenate (EMIm(HF)2.3F) room temperature ionic liquid (RTIL). Al–air batteries can sustain current densities up to 1.5 mA cm−2, producing capacities above 140 mA h cm−2, thus utilizing above 70% of the theoretical Al capacity. This is equivalent to an outstanding energy densities of 2300 W h kg−1 and 6200 W h L−1. We detected Al2O3 at the air electrode as the battery discharge product of the oxygen reduction coupled with Al ions migrated to the air electrode.

Influence of Solution Volume on the Dissolution Rate of Silicon Dioxide in Hydrofluoric Acid

Experimental data and modeling of the dissolution of various Si/SiO2 thermal coatings in different volumes of hydrofluoric acid (HF) are reported. The rates of SiO2 -film dissolution, measured by means of various electrochemical techniques, and alteration in HF activity depend on the thickness of the film coating. Despite the small volumes (0.6-1.2 mL) of the HF solution, an effect of SiO2 -coating thickness on the dissolution rate was detected. To explain alterations detected in HF activity after SiO2 dissolution, spectroscopic analyses (NMR and FTIR) of the chemical composition of the solutions were conducted. This is associated with a modification in the chemical composition of the HF solution, which results in either the formation of an oxidized species in solution or the precipitation of dissolution products. HF2 (-) accumulation in the HF solution, owing to SiO2 dissolution was identified as the source of the chemical alteration.

Challenges and Prospect of Non-aqueous Non-alkali (NANA) Metal–Air Batteries

Non-aqueous non-alkali (NANA) metal–air battery technologies promise to provide electrochemical energy storage with the highest specific energy density. Metal–air battery technology is particularly advantageous being implemented in long-range electric vehicles. Up to now, almost all the efforts in the field are focused on Li–air cells, but other NANA metal–air battery technologies emerge. The major concern, which the research community should be dealing with, is the limited and rather poor rechargeability of these systems. The challenges we are covering in this review are related to the initial limited discharge capacities and cell performances. By comprehensively reviewing the studies conducted so far, we show that the implementation of advanced materials is a promising approach to increase metal–air performance and, particularly, metal surface activation as a prime achievement leading to respectful discharge currents. In this review, we address the most critical areas that need careful research attention in order to achieve progress in the understanding of the physical and electrochemical processes in non-aqueous electrolytes applied in beyond lithium and zinc air generation of metal–air battery systems.

Improvement of Aluminum–Air Battery Performances by the Application of Flax Straw Extract

The effect of a flax straw extract on Al corrosion inhibition in a strong alkaline solution was studied by using electrochemical measurements, weight-loss analysis, SEM, and FTIR spectroscopy. Flax straw extract added (3 vol %) to the 5 m KOH solution to act as a mixed-type Al corrosion inhibitor. The electrochemistry of Al in the presence of a flax straw extract in the alkaline solution, the effect of the extract on the Al morphology and surface films formed, and the corrosion inhibition mechanism are discussed. Finally, the Al-air battery discharge capacity recorded from a cell that used the flax straw extract in the alkaline electrolyte is substantially higher than that with only a pure alkaline electrolyte. This improved sustainability of the Al anode is attributed to Al corrosion inhibition and, consequently, to hydrogen evolution suppression.