Mechanistic Role of Li<sup>+</sup> Dissociation Level in Aprotic Li–O<sub>2</sub> Battery

Sharon, Daniel; Hirsberg, Daniel; Salama, Michael; Afri, Michal; Frimer, Aryeh A.; Noked, Malachi; Kwak, Won‐Jin; Sun, Yang Kook; Aurbach, Doron

doi:10.1021/acsami.5b11483

Cited by 127 publications

(161 citation statements)

References 38 publications

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“…Furthermore, a considerable proportion of toroidal precipitates were formed on the separator in Li[TFA]/G3 (Li[TFA]: lithium trifluoroacetate) (Figure 1e). It has been confirmed by various authors that the distinctive toroidal precipitates are predominantly Li 2 O 2 , 2,3,1014 the main discharge product in the Li-O 2 battery. From these, it is considered that the precipitate observed on the separators is also Li 2 O 2 .…”

Section: Abstract: Li-o 2 Battery | Lithium Superoxide | Anionmentioning

confidence: 74%

“…2,3,12,13,15 However, the Li 2 O 2 on the separator observed here offers an alternative viewpoint on a suitable direction for optimization of the Li-O 2 battery. Previous studies have shown that the morphology of the discharge product observed on the cathode surface changes…”

Section: •¹mentioning

confidence: 91%

“…2,3 The morphology has also been shown to affect the charging potential, 4 and thus directly influences the energy efficiency. However, a little-considered aspect is the extent to which the solubility of the O 2…”

Section: •¹mentioning

confidence: 99%

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Effect of Anion in Glyme-based Electrolyte for Li-O₂ Batteries: Stability/Solubility of Discharge Intermediate

et al. 2017

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This study demonstrates that the amount of discharge product (Li 2 O 2 ) precipitated on the separator in a lithium oxygen cell using glyme-based electrolytes depends on the anion. The stability of the discharge intermediate (LiO 2 ) in the electrolyte has been shown to depend on the anionic species, which is related to Li 2 O 2 precipitation on the separator. The implications for producing an efficient and long-life Li-O 2 cell are elaborated. Keywords: Li-O 2 battery | Lithium superoxide | AnionThe Li-O 2 battery has been attracting a great deal of attention due to its high theoretical energy density.1 The solubility of the) is a critical parameter, because its solubility is believed to directly affect the morphology of the final discharge product, Li 2 O 2 .2 This morphology determines the rate of cathode clogging, thus also the maximum discharge capacity.2,3 The morphology has also been shown to affect the charging potential, 4 and thus directly influences the energy efficiency. However, a little-considered aspect is the extent to which the solubility of the O 2•¹ may allow the transport of reduced O 2 species away from the electrode. Nazar et al. reported SEM observation of discharge product deposition on glass fiber (separator) for a cell using 1 M lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA])/tetraethylene glycol dimethyl ether (G4) electrolyte. 5 The implications, in terms of cell cyclability, of precipitation of discharge product on an electronically nonconductive component of the cell are self-evident. Moreover, Liu et al. have demonstrated the presence of large amounts of predominantly amorphous precipitates in the separator of a Li-O 2 battery using a 1 M lithium trifluoromethanesulfonate (Li[OTf])/ G4 electrolyte, and commented on their detrimental effects on cell overpotential and cyclability. 6 In their later work, they also reported X-ray diffraction-based evidence for crystalline Li 2 O 2 in the separator.7 A means to tune the degree of discharge product loss to the separator (and elsewhere in the cell) by variation of the electrolyte properties is thus desirable. The effect of variation of electrolyte, and in particular the anion, on this phenomenon has not yet been reported, to the best of our knowledge.In this study, we present an analysis of the variation of O 2•¹ solubility, and its subsequent effect on Li 2 O 2 distribution in the cell, for a series of glyme-based electrolyte solutions. In our previous study, 8 we applied a 1:1 mixture of Li salt and glyme for oxygen reduction/evolution. We have also recently shown that variation of the anion in such 1:1 solutions results in large differences in the amount of free glyme depending on the choice of Li salt. 9 Thus, to fully characterize the direct effect of the anion on the intermediate solubility and stability, we have chosen to explore more dilute solutions in this study, in which the effects may be more easily observed. The molar ratio of lithium salt to triethylene glycol dimethyl ether (G3) was kept constant (1:4), and the vario...

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Section: Abstract: Li-o 2 Battery | Lithium Superoxide | Anionmentioning

confidence: 74%

Section: •¹mentioning

confidence: 91%

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Effect of Anion in Glyme-based Electrolyte for Li-O₂ Batteries: Stability/Solubility of Discharge Intermediate

et al. 2017

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“…High DN salts have been shown to increase the capacity 4‐fold 6a, 8. Redox shuttles are able to transfer electrons from the electrode to O 2 in solution thus forming LiO 2 away from the electrode surface 9.…”

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confidence: 99%

Phenol‐Catalyzed Discharge in the Aprotic Lithium‐Oxygen Battery

et al. 2017

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Discharge in the lithium‐O2 battery is known to occur either by a solution mechanism, which enables high capacity and rates, or a surface mechanism, which passivates the electrode surface and limits performance. The development of strategies to promote solution‐phase discharge in stable electrolyte solutions is a central challenge for development of the lithium‐O2 battery. Here we show that the introduction of the protic additive phenol to ethers can promote a solution‐phase discharge mechanism. Phenol acts as a phase‐transfer catalyst, dissolving the product Li2O2, avoiding electrode passivation and forming large particles of Li2O2 product—vital requirements for high performance. As a result, we demonstrate capacities of over 9 mAh cm−2 areal, which is a 35‐fold increase in capacity compared to without phenol. We show that the critical requirement is the strength of the conjugate base such that an equilibrium exists between protonation of the base and protonation of Li2O2.

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“…[6a, 8] Redox shuttles are able to transfer electrons from the electrode to O 2 in solution thus forming LiO 2 away from the electrode surface.…”

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confidence: 99%

Phenol‐Catalyzed Discharge in the Aprotic Lithium‐Oxygen Battery

et al. 2017

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Discharge in the lithium-O 2 battery is knownt o occur either by as olution mechanism, whiche nables high capacity and rates,o rasurface mechanism, which passivates the electrode surface and limits performance.The development of strategies to promote solution-phase dischargei ns table electrolyte solutions is ac entral challenge for development of the lithium-O 2 battery.H ere we show that the introduction of the protic additive phenol to ethers can promote as olutionphase discharge mechanism. Phenol acts as ap hase-transfer catalyst, dissolving the product Li 2 O 2 ,a voiding electrode passivation and forming large particles of Li 2 O 2 productvital requirements for high performance.A saresult, we demonstrate capacities of over 9mAh cm À2 areal ,w hichi sa35-fold increase in capacity compared to without phenol. We show that the critical requirement is the strength of the conjugate base such that an equilibrium exists between protonation of the base and protonation of Li 2 O 2 .

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Mechanistic Role of Li⁺ Dissociation Level in Aprotic Li–O₂ Battery

Cited by 127 publications

References 38 publications

Effect of Anion in Glyme-based Electrolyte for Li-O₂ Batteries: Stability/Solubility of Discharge Intermediate

Effect of Anion in Glyme-based Electrolyte for Li-O₂ Batteries: Stability/Solubility of Discharge Intermediate

Phenol‐Catalyzed Discharge in the Aprotic Lithium‐Oxygen Battery

Phenol‐Catalyzed Discharge in the Aprotic Lithium‐Oxygen Battery

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Mechanistic Role of Li+ Dissociation Level in Aprotic Li–O2 Battery

Cited by 127 publications

References 38 publications

Effect of Anion in Glyme-based Electrolyte for Li-O2 Batteries: Stability/Solubility of Discharge Intermediate

Effect of Anion in Glyme-based Electrolyte for Li-O2 Batteries: Stability/Solubility of Discharge Intermediate

Phenol‐Catalyzed Discharge in the Aprotic Lithium‐Oxygen Battery

Phenol‐Catalyzed Discharge in the Aprotic Lithium‐Oxygen Battery

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Mechanistic Role of Li⁺ Dissociation Level in Aprotic Li–O₂ Battery

Effect of Anion in Glyme-based Electrolyte for Li-O₂ Batteries: Stability/Solubility of Discharge Intermediate

Effect of Anion in Glyme-based Electrolyte for Li-O₂ Batteries: Stability/Solubility of Discharge Intermediate