Understanding the behavior of Li–oxygen cells containing LiI

Kwak, Won‐Jin; Hirshberg, Daniel; Sharon, Daniel; Shin, Hyeon‐Ji; Afri, Michal; Park, Jin‐Bum; Garsuch, Arnd; Chesneau, Frédérick; Frimer, Aryeh A.; Aurbach, Doron; Sun, Yang Kook

doi:10.1039/c5ta01399b

Cited by 193 publications

(263 citation statements)

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“…Although the formation of side products occurs in all solvents, it is less severe in ether-based cells than in carbonate-based ones 129,144 . In a recent series of papers [146][147][148][149] , it was demonstrated that all relevant non-aqueous solvents are reactive towards basic and nucleophilic O 2 reduction products (that is, superoxide and peroxide moieties) in the solution phase containing highly electrophilic Li ions. We note that all carbonaceous electrode materials can degrade by reacting with superoxide and peroxide moieties.…”

Section: Metal-oxygen Battery Systems Secondary Li-o 2 Batteries Wermentioning

confidence: 99%

Promise and reality of post-lithium-ion batteries with high energy densities

2016

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What characteristics define a good rechargeable battery? Although properties such as rate capability, cost, cycle life and temperature tolerance must be taken into consideration in any evaluation of a rechargeable battery 1,2 , it is the improvement in energy density that has primarily driven the overall technological progress over the past 150 years -from lead-acid cells in the 1850s, nickelcadmium cells in the 1890s and nickel metal hydride cells in the 1960s to, finally, lithium-ion batteries (LIBs) in the present day.In the current era of LIBs, there is an ever-growing demand for even higher energy densities to power mobile IT devices with increased power consumption and to extend the driving range of electric vehicles. The growth of the global electric vehicle market has been slower than initially predicted about 5 years ago 3 , which reflects the challenge that the battery industry faces: customers react very sensitively to the driving range (and thus the energy density) and price of electric vehicles. Because the energy density of a rechargeable battery is determined mainly by the specific capacities and operating voltages of the anode and the cathode, active materials have been the main focus of research in recent years. Other cell components, including separators, binders, outer cases and, to some extent, the major components of the electrolyte solution (that is, solvent and salt), have little room for further improvement. In other words, a dramatic increase in the energy density requires new redox chemistries between charge-carrier ions and host materials beyond the conventional 'intercalation' mechanisms 4 . Intercalationbased materials have a relatively small number of crystallographic sites for storing charge-carrier ions, leading to limited energy densities. For this reason, the electrodes that operate on the basis of distinct solid-state reactions, such as alloying and conversion, or that use gas-phase reactants have encountered growing interest owing to the likelihood that they will surpass the energy densities of intercalation-based electrodes.New chemistries for charge-carrier ion storage serve as the basis for 'beyond intercalation' or so-called postLIBs 5-7 . The systems governed by these new chemistries offer higher theoretical energy densities, and this benefit is usually translated to, at least, the initial cycles in experimental testing. It is becoming increasingly evident that the short lifetime is a serious problem of post-LIB systems. Indeed, the main technological challenge associated with these systems is overcoming their inferior reversibility. The main factors responsible for the low reversibility are instabilities during the phase transition of active materials and/or uncontrolled reactions at the electrode/electrolyte interface 8 ; this implies that the electrode structures and electrolyte solutions should be developed and optimized as integrated systems to enable the realization of post-LIBs.In this Review, we discuss a wide range of promising post-LIBs, focusing on their advant...

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Section: Metal-oxygen Battery Systems Secondary Li-o 2 Batteries Wermentioning

confidence: 99%

Promise and reality of post-lithium-ion batteries with high energy densities

2016

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“…2. In this case, the minimum potential required to oxidize Li 2 O 2 (s) is 2.96 V, and the iodide/triiodide redox couple possesses the required driving force to carry out this reaction, as shown in several experiments (6).…”

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confidence: 88%

“…Previous reports have shown empirical evidence of parasitic reactions associated with iodide/triiodide redox couples in a Li-O 2 battery with ethereal solvents (6,7). Such irreversible routes obviously need to be avoided to allow long-term rechargeability in a Li-O 2 battery.…”

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Comment on “Cycling Li-O ₂ batteries via LiOH formation and decomposition”

Viswanathan

Pande

Abraham

et al. 2016

Science

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Based on a simple thermodynamic analysis, we show that iodide-mediated electrochemical decomposition of lithium hydroxide (LiOH) likely occurs through a different mechanism than that proposed by Liu et al. (Research Article, 30 October 2015, p. 530 Although no thermodynamic barriers exist for the LiI-mediated formation of LiOH during discharge of water-contaminated Li-O 2 cells, the charging process warrants further analysis. We present a simple thermodynamic analysis of the triiodide-mediated LiOH oxidation mechanism proposed in their work (1). We consider their overall proposed charging reaction.This reaction has an equilibrium potential of 3.34 V under standard conditions (2). The activity of water is not at standard conditions in these experiments, but even at parts per million (ppm) quantities of water, there are negligible changes to the equilibrium potential. For example, in an experiment with~100 to 45,000 ppm, this corresponds to an equilibrium potential shift of~0.02 to 0.009 V.We now consider the iodide/triiodide redox reaction, shown in figure 4 of (1), given byThe redox potential for this reaction depends on the solvent (3). As reported in (1), we use the equilibrium potential-i.e.,~3.0 V-as shown in figure 1 of (1). Liu et al. point out in the caption that the crossing points of the charge/discharge curves indicate the positions of the redox potential of I − /I 3 − in the specific electrode/electrolyte system. The chemical reaction, shown in figure 4 of (1), to complete the charging cycle, is given byThis chemical reaction is uphill in free energy by DG c2 = 4 × (3.347 − 3.00) = 1.39 eV. This corresponds to an equilibrium constant, given by. Even if every cathode site were electrochemically active, the fraction that would transform to the product, O 2 , would be exceptionally small and therefore cannot account for a reversible process regenerating O 2 .The overall free-energy diagram for the charging mechanism proposed by Liu et al. at U = 3 V is shown in Fig. 1. A simpler way to understand the inconsistency is that the minimum potential required to oxidize LiOH is 3.34 V. The iodide/ triiodide redox couple has an oxidation potential of only~3 V and hence it is not feasible to oxidize LiOH(s) with such a scheme.In a rigorously anhydrous Li-O 2 battery that produces Li 2 O 2 as the discharge product (4, 5), the free-energy diagram involving an iodide/ triiodide redox couple is shown in Fig. 2

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“…One of the requirements for the mediator is its stability to the electrochemical conditions, in effect we found UV-visible spectroscopy evidence that oxygen actually reacts with the mediator iodide [31]. Other authors instead have shown that the product may also be significantly affected by iodide [32]. By comparing Figure 12 with Figure 11 we could not notice any remarkable difference in the morphology or composition of fully discharged electrodes with or without iodide.…”

Section: Redox Mediators and Rechargementioning

confidence: 55%

Studies of Lithium-Oxygen Battery Electrodes by Energy- Dependent Full-Field Transmission Soft X-Ray Microscopy

Tonti¹,

Olivares-Marín²,

Sorrentino³

et al. 2017

X-Ray Characterization of Nanostructured Energy Materials by Synchrotron Radiation

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Energy-dependent full-field transmission soft X-ray microscopy is a powerful technique that provides chemical information with spatial resolution at the nanoscale. Oxygen K-level transitions can be optimally detected, and we used this technique to study the discharge products of lithium-oxygen batteries, where this element undergoes a complex chemistry, involving at least three different oxidation states and formation of nanostructured deposits. We unambiguously demonstrated the presence of significant amounts of superoxide forming a composite with peroxide, and secondary products such as carbonates or hydroxide. In this chapter, we describe the technique from the fundamental to the observation of discharged electrodes to illustrate how this tool can help obtaining a more comprehensive view of the phenomena taking place in metal air batteries and any system involving nanomaterials with a complex chemistry.

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Understanding the behavior of Li–oxygen cells containing LiI

Abstract: This work deals with core issues of Li–oxygen battery systems; intrinsic stability of polyether electrolyte solutions and the role of important redox mediators such as LiI/I2.

Cited by 193 publications

References 44 publications

Promise and reality of post-lithium-ion batteries with high energy densities

Promise and reality of post-lithium-ion batteries with high energy densities

Comment on “Cycling Li-O ₂ batteries via LiOH formation and decomposition”

Studies of Lithium-Oxygen Battery Electrodes by Energy- Dependent Full-Field Transmission Soft X-Ray Microscopy

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Understanding the behavior of Li–oxygen cells containing LiI

Abstract: This work deals with core issues of Li–oxygen battery systems; intrinsic stability of polyether electrolyte solutions and the role of important redox mediators such as LiI/I2.

Cited by 193 publications

References 44 publications

Promise and reality of post-lithium-ion batteries with high energy densities

Promise and reality of post-lithium-ion batteries with high energy densities

Comment on “Cycling Li-O 2 batteries via LiOH formation and decomposition”

Studies of Lithium-Oxygen Battery Electrodes by Energy- Dependent Full-Field Transmission Soft X-Ray Microscopy

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Comment on “Cycling Li-O ₂ batteries via LiOH formation and decomposition”