Deactivation of carbon electrode for elimination of carbon dioxide evolution from rechargeable lithium-oxygen cells (original) (raw)
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The Role of Ionic Liquid in Oxygen Reduction Reaction for Lithium-air Batteries
Electrochimica Acta, 2017
We have investigated the oxygen reduction reaction (ORR) in the presence of non-aqueous electrolytes in an attempt to overcome the challenges related to lithium-air batteries, such as low reversibility, poor rate capability, and electrode/solvent stability. We have used glassy carbon as the working electrode in electrolytes composed of lithium bis(trifluoromethanesulfonyl)imide and 1,2dimethoxyethane or N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI, ionic liquid). We have employed the kinetic model to treat the electrochemical impedance spectroscopy data. This approach provides the rate constants for each of the elementary steps and allows indirect investigation of the role played by the ionic liquid in the ORR. The ionic liquid shifts the onset potential of the ORR to more positive values. The presence of the large Pyr14 + cation increases the ratedetermining step by approximately three orders of magnitude as compared to the ether-based electrolyte. This ionic liquid is chemically resistant to degradation reactions and increases the rate of the ORR, which makes it a promising candidate for use in lithium-air batteries.
The Catalytic Behavior of Lithium Nitrate in Li-O2 Batteries
ECS Meeting Abstracts
Over the last decade extra efforts were invested in the development of aprotic Li-O2 cells. Early research presented optimistic results that showed the great potential of this system. However in recent years more research works observed that it is hard to find suitable cell components that will enable prolong cycling of Li-O2 cells. Many challenges need to be addressed. Two dominant subjects were given special attention: the carbon cathodes and the electrolyte solutions. These factors governed Li-O2 cells’ operation during both the oxygen reduction reaction (ORR) and the oxygen evaluation reaction (OER). Despite many attempts to find solvents that are stable toward active oxygen species formed by oxygen reduction (super-oxide, peroxide moieties) , no solvent was found to be fully stable during ORR & OER. Several sovents were explored and although none of them was found to be stable, they presented difference features that can affect positively the ORR. One parameter is the Guttma...
Hierarchical activated carbon microfiber (ACM) electrodes for rechargeable Li–O2 batteries
Journal of Materials Chemistry A, 2013
Hierarchical activated carbon microfiber (ACM) and ACM/a-MnO 2 nanoparticle hybrid electrodes were fabricated for high performance rechargeable Li-O 2 batteries. Various oxygen diffusion channels present in these air-cathodes were not blocked during the oxygen reduction reactions (ORR) in triglyme-LiTFSI (1 M) electrolyte solution. ACM and ACM/a-MnO 2 hybrid electrodes exhibited a maximum specific capacity of 4116 mA h g c À1 and 9000 mA h g c À1 , respectively, in comparison to 2100 mA h g c À1 for conventional carbon composite air-electrodes. Energy densities of these electrodes were remarkably higher than those of sulfur cathodes and the most promising lithium insertion electrodes. In addition, ACM and ACM/a-MnO 2 hybrid electrodes exhibited lower charge voltages of 4.3 V and 3.75 V respectively compared to 4.5 V for conventional composite carbon electrodes. Moreover, these binder free electrodes demonstrated improved cycling performances in contrast to the carbon composite electrodes. The superior electrochemical performance of these binder free microfiber electrodes has been attributed to their extremely high surface area, hierarchical microstructure and efficient ORR catalysis by a-MnO 2 nanoparticles. The results showed herein demonstrate that the air-cathode architecture is a critical factor determining the electrochemical performance of rechargeable Li-O 2 batteries. This study also demonstrates the instability of ether based electrolyte solutions during oxygen reduction reactions, which is a critical problem for Li-O 2 batteries.
Chemistry of Materials, 2012
The high capacity of the layered Li−excess oxide cathode is always accompanied by extraction of a significant amount of oxygen from the structure. The effects of oxygen on the electrochemical cycling are not well understood. Here, the detailed reaction scheme following oxygen evolution was established using real-time gas analysis and ex situ chemical analysis of the surface of the electrodes. A series of electrochemical/chemical reactions involving oxygen radicals constantly produced and decomposed lithium carbonate during cell operation. Moreover, byproducts, including water, affected the cycle life and rate capability: hydrolysis of the electrolyte salt formed hydrofluoric acid that attacked the surface of the electrode. This finding implies that protection of the electrode surface from damage, for example, by a coating or removal of oxygen radicals by scavengers, will be critical to widespread usage of Li−excess transition metal oxides in rechargeable lithium batteries.
Electrochimica Acta, 2014
Lithium-air batteries with an aqueous alkaline electrolyte promise a very high practical energy density and capacity. These batteries are mainly limited by high overpotentials on the bifunctional cathode during charge and discharge. To reduce overpotentials the bifunctional cathode of such batteries must be improved significantly. Nickel is relatively inexpensive and has a good catalytic activity in alkaline media. Co 3 O 4 was found to be a promising metal oxide catalyst for oxygen evolution in alkaline media but it has a low electronic conductivity. On the other hand since nickel has a good electronic conductivity Co 3 O 4 can be added to pure nickel electrodes to enhance performance due to a synergetic effect. Due to the poor stability of carbon materials at high anodic potentials, gas diffusion electrodes were prepared without carbon to improve especially long-term stability. Gas diffusion electrodes were electrochemically investigated in a half cell. In addition, cyclic voltammogrametry (CV) and electrochemical impedance spectroscopy (EIS) were carried out. SEM was used for the physical and morphological investigations. Investigations showed that electrodes containing 20 wt.% Co 3 O 4 exhibited the highest performance.
Rechargeable-battery chemistry based on lithium oxide growth through nitrate anion redox
Nature Chemistry, 2019
Next-generation lithium-battery cathodes often involve the growth of lithium-rich phases, which enables specific capacities that 2-3 times higher than insertion cathode materials such as lithium cobalt oxide (LiCoO 2). Here, we investigate battery chemistry previously deemed irreversible in which lithium oxide (Li 2 O), a lithium-rich phase, grows through reduction of the nitrate anion in a lithium nitrate-based molten salt at 150 °C. Using a suite of independent characterization techniques, we demonstrate that a Ni nanoparticle catalyst enables the reversible growth and dissolution of micron-sized Li 2 O crystals through the effective catalysis of nitrate reduction and nitrite oxidation, resulting in high cathode areal capacities (~12 mAh/cm 2). These results enable a rechargeable battery system that has a full-cell theoretical specific energy of 1579 Wh/kg, in which a molten nitrate salt serves as both active material and electrolyte.
The mechanisms of oxygen reduction and evolution reactions in nonaqueous lithium-oxygen batteries
ChemSusChem, 2014
A fundamental understanding of the mechanisms of both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in nonaqueous lithium-oxygen (Li-O2) batteries is essential for the further development of these batteries. In this work, we systematically investigate the mechanisms of the ORR/OER reactions in nonaqueous Li-O2 batteries by using electron paramagnetic resonance (EPR) spectroscopy, using 5,5-dimethyl-pyrroline N-oxide as a spin trap. The study provides direct verification of the formation of the superoxide radical anion (O2(˙-)) as an intermediate in the ORR during the discharge process, while no O2(˙-) was detected in the OER during the charge process. These findings provide insight into, and an understanding of, the fundamental reaction mechanisms involving oxygen and guide the further development of this field.