A novel aqueous lithium-oxygen cell based on the oxygen-peroxide redox couple (original) (raw)
Related papers
Liquid-Free Lithium-Oxygen Batteries
Angewandte Chemie, 2014
non-aqueous Li-O 2 batteries are considered as most advanced power sources, albeit they are facing numerous challenges concerning almost each cell component. Herein, we diverge from the conventional and traditional liquid-based nonaqueous Li-O 2 batteries to a solid polymer electrolyte (SPE) Li-O 2 system, operated at a temperature higher than the melting point of the polymer electrolyte, where useful and most applicable conductivity values are easily achieved. The proposed SPE-based Li-O 2 cell is compared to glyme-based Li-O 2 cells through potentiodynamic and galvanostatic studies, showing higher cell discharge voltage by 80mV and most significantly, a charge voltage lower by ∼400mV. The solid state battery demonstrated a comparable discharge specific capacity to glyme-based Li-O 2 cells when discharged at the same current density. The discharge products were identified as lithium peroxide by XRD analysis and FT-IR combined with quantitative 1 H and qualitative 13 C NMR spectroscopies identified lower molecular PEO as the main degradation products, as well as in-chain ester and formates in negligible amounts. The results shown here demonstrate that safer PEO-based Li-O 2 battery is highly advantageous and can potentially replace liquid-based cells contingent upon further investigation.
The Journal of Physical Chemistry Letters, 2016
Fundamental understanding of growth mechanisms of Li 2 O 2 in Li−O 2 cells is critical for implementing batteries with high gravimetric energies. Li 2 O 2 growth can occur first by 1e − transfer to O 2 , forming Li + −O 2 − and then either chemical disproportionation of Li + −O 2 − , or a second electron transfer to Li + −O 2 −. We demonstrate that Li 2 O 2 growth is governed primarily by disproportionation of Li + −O 2 − at low overpotential, and surface-mediated electron transfer at high overpotential. We obtain evidence supporting this trend using the rotating ring disk electrode (RRDE) technique, which shows that the fraction of oxygen reduction reaction charge attributable to soluble Li + −O 2 −-based intermediates increases as the discharge overpotential reduces. Electrochemical quartz crystal microbalance (EQCM) measurements of oxygen reduction support this picture, and show that the dependence of the reaction mechanism on the applied potential explains the difference in Li 2 O 2 morphologies observed at different discharge overpotentials: formation of large (∼250 nm−1 μm) toroids, and conformal coatings (<50 nm) at higher overpotentials. These results highlight that RRDE and EQCM can be used as complementary tools to gain new insights into the role of soluble and solid reaction intermediates in the growth of reaction products in metal−O 2 batteries.
Key scientific challenges in current rechargeable non-aqueous Li–O2 batteries: experiment and theory
Rechargeable Li-air (henceforth referred to as Li-O 2 ) batteries provide theoretical capacities that are ten times higher than that of current Li-ion batteries, which could enable the driving range of an electric vehicle to be comparable to that of gasoline vehicles. These high energy densities in Li-O 2 batteries result from the atypical battery architecture which consists of an air (O 2 ) cathode and a pure lithium metal anode. However, hurdles to their widespread use abound with issues at the cathode (relating to electrocatalysis and cathode decomposition), lithium metal anode (high reactivity towards moisture) and due to electrolyte decomposition. This review focuses on the key scientific challenges in the development of rechargeable non-aqueous Li-O 2 batteries from both experimental and theoretical findings. This dual approach allows insight into future research directions to be provided and highlights the importance of combining theoretical and experimental approaches in the optimization of Li-O 2 battery systems.
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.
New Electrode and Electrolyte Configurations for Lithium-Oxygen Battery
Chemistry - A European Journal, 2018
We report herein cathode configurations alternative to the most diffused ones for application in lithium-oxygen batteries using an ionic liquid-based electrolyte. The electrodes employ high surface area conductive carbon as the reaction host and polytetrafluoroethylene as the binding agent to enhance ORR/OER reversibility. Roll-pressed, self-standing electrodes (SSEs) and thinner, spray deposited electrodes (SDEs) are characterized in lithium-oxygen cells using an ionic liquid (IL) based electrolyte formed by mixing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt in N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethanesulfonyl)imide (DEMETFSI). The electrochemical results reveal reversible reaction for both electrode
LithiumOxygen Electrochemistry in Non-Aqueous Solutions
Israel Journal of Chemistry, 2015
Pairing lithium and oxygen in aprotic solvents can theoretically lead to one of the most promising electrochemical cells available. If successful, this system could compete with technologies such as the internal combustion engine and provide an energy density that can accommodate electric vehicle demands. However, there are many problems that have inhibited this technology from becoming realistic. One of the main reasons is capacity fading after only a few cycles, which is caused by the instability of electrolyte solutions in the presence of reduced oxygen species like O 2 C À and O 2 2À. In recent years, using various analytical tools, researchers have been able to isolate the breakdown products arising from the reactions occurring between the aprotic solvent and the reduced oxygen species. Nevertheless, no solvents have yet been found that are fully stable throughout the reduction and oxidation processes. However, an understanding of these decomposition mechanisms can help us in designing new systems that are more stable toward the aggressive conditions taking place in LiÀO 2 cell operation. This review will include analytical studies on the most widely used solvents in current LiÀO 2 research.
Reaction chemistry in rechargeable Li-O2 batteries
Chemical Society reviews, 2017
The seemingly simple reaction of Li-O2 batteries involving lithium and oxygen makes this chemistry attractive for high-energy-density storage systems; however, achieving this reaction in practical rechargeable Li-O2 batteries has proven difficult. The reaction paths leading to the final Li2O2 discharge products can be greatly affected by the operating conditions or environment, which often results in major side reactions. Recent research findings have begun to reveal how the reaction paths may be affected by the surrounding conditions and to uncover the factors contributing to the difficulty in achieving the reactions of lithium and oxygen. This progress report describes the current state of understanding of the electrode reaction mechanisms in Li-O2 batteries; the factors that affect reaction pathways; and the effect of cell components such as solvents, salts, additives, and catalysts on the discharge product and its decomposition during charging. This comprehensive review of the r...
Redox shuttle and positive electrode protection for Li-O2 systems
2017
The present PhD work focuses on solving two major issues of the Li-O2 positive electrodes, both being linked with the nature of the discharge product formed during the Oxygen Reduction Reaction, in Lithium cation electrolyte: Lithium peroxide (Li2O2). The first issue is related to the Discharge mechanism (consecutives Electrochemical nucleation and chemical disproportionation of an intermediate, lithium superoxide), which lead to the formation of large particles of lithium peroxide on the electrode surface. Owing to their size and resistivity (bandgap of lithium peroxide : 5 eV), it is nearly impossible to re-charge efficiently the electrode. This issue can be solved, thanks to the dissolution of an additive in solution, that promote the transport of electrons, and allow the oxidation of large discharge particles (in theory, even the ones disconnected from the electrode). A very good compound was found to efficiently work as a redox shuttle (enhanced Oxygen Evolution reaction), with...
Implications of 4 e– Oxygen Reduction via Iodide Redox Mediation in Li–O2 Batteries
ACS Energy Letters, 2016
The nonaqueous lithium−oxygen (Li−O 2) electrochemistry has garnered significant attention because of its high theoretical specific energy compared to the state-of-the-art lithium-ion battery. The common active nonaqueous Li−O 2 battery cathode electrochemistry is the formation (discharge) and decomposition (charge) of lithium peroxide (Li 2 O 2). Recent reports suggest that the introduction of lithium iodide (LiI) to an ether-based electrolyte containing water at impurity levels induces a 4 e − oxygen reduction reaction forming lithium hydroxide (LiOH) potentially mitigating instability issues related to typical Li 2 O 2 formation. We provide quantitative analysis of the influence of LiI and H 2 O on the electrochemistry in a common Li−O 2 battery employing an ether-based electrolyte and a carbon cathode. We confirm, through numerous quantitative techniques, that the addition of LiI and H 2 O promotes efficient 4 e − oxygen reduction to LiOH on discharge, which is unexpected given that only 2 e − oxygen reduction is typically observed at undoped carbon electrodes. Unfortunately, LiOH is not reversibly oxidized to O 2 on charge, where instead a complicated mix of redox shuttling and side reactions is observed.