| 1. |
- Liu, Tao, et al.
(author)
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Understanding LiOH Formation in a Li-O2 Battery with LiI and H2O Additives
- 2019
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In: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 9:1, s. 66-77
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Journal article (peer-reviewed)abstract
- LiI-promoted LiOH formation in Li-O2 batteries with wet ether electrolytes has been investigated by Raman, nuclear magnetic resonance spectroscopy, operando pressure tests, and molecular dynamics simulations. We find that LiOH formation is a synergistic effect involving both H2O and LiI additives, whereas with either alone Li2O2 forms. LiOH is generated via a nominal four-electron oxygen reduction reaction, the hydrogen coming from H2O and the oxygen from both O2 and H2O, and with fewer side reactions than typically associated with Li2O2 formation; the presence of fewer parasitic reactions is attributed to the proton donor role of water, which can coordinate to O2- and the higher chemical stability of LiOH. Iodide plays a catalytic role in decomposing H2O2/HO2- and thereby promoting LiOH formation, its efficacy being highly dependent on the water concentration. This iodide catalysis becomes retarded at high water contents due to the formation of large water-solvated clusters, and Li2O2 forms again.
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| 2. |
- Temprano, Israel, et al.
(author)
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Toward Reversible and Moisture-Tolerant Aprotic Lithium-Air Batteries
- 2020
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In: Joule. - : Elsevier BV. - 2542-4351. ; 4:11, s. 2501-2520
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Journal article (peer-reviewed)abstract
- The development of moisture-tolerant, LiOH-based non-aqueous Li-O2 batteries is a promising route to bypass the inherent limitations caused by the instability of their typical discharge products, LiO2 and Li2O2. The use of the I−/I3− redox couple to mediate the LiOH-based oxygen reduction and oxidation reactions has proven challenging due to the multiple reaction paths induced by the oxidation of I− on cell charging. In this work, we introduce an ionic liquid to a glyme-based electrolyte containing LiI and water and demonstrate a reversible LiOH-based Li-O2 battery cycling that operates via a 4 e−/O2 process with a low charging overpotential (below 3.5 V versus Li/Li+). The addition of the ionic liquid increases the oxidizing power of I3−, shifting the charging mechanism from IO−/IO3− formation to O2 evolution.
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| 3. |
- Zhao, Evan Wenbo, et al.
(author)
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In situ NMR metrology reveals reaction mechanisms in redox flow batteries
- 2020
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 579:7798, s. 224-228
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Journal article (peer-reviewed)abstract
- Large-scale energy storage is becoming increasingly critical to balancing renewable energy production and consumption1. Organic redox flow batteries, made from inexpensive and sustainable redox-active materials, are promising storage technologies that are cheaper and less environmentally hazardous than vanadium-based batteries, but they have shorter lifetimes and lower energy density2,3. Thus, fundamental insight at the molecular level is required to improve performance4,5. Here we report two in situ nuclear magnetic resonance (NMR) methods of studying redox flow batteries, which are applied to two redox-active electrolytes: 2,6-dihydroxyanthraquinone (DHAQ) and 4,4′-((9,10-anthraquinone-2,6-diyl)dioxy) dibutyrate (DBEAQ). In the first method, we monitor the changes in the 1H NMR shift of the liquid electrolyte as it flows out of the electrochemical cell. In the second method, we observe the changes that occur simultaneously in the positive and negative electrodes in the full electrochemical cell. Using the bulk magnetization changes (observed via the 1H NMR shift of the water resonance) and the line broadening of the 1H shifts of the quinone resonances as a function of the state of charge, we measure the potential differences of the two single-electron couples, identify and quantify the rate of electron transfer between the reduced and oxidized species, and determine the extent of electron delocalization of the unpaired spins over the radical anions. These NMR techniques enable electrolyte decomposition and battery self-discharge to be explored in real time, and show that DHAQ is decomposed electrochemically via a reaction that can be minimized by limiting the voltage used on charging. We foresee applications of these NMR methods in understanding a wide range of redox processes in flow and other electrochemical systems.
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