A comprehensive study on the cell chemistry of the sodium superoxide (NaO2) battery

Hartmann, Pascal; Bender, Conrad L.; Sann, Joachim; Dürr, Anna Katharina; Jansen, Martin; Janek, Jürgen; Adelhelm, Philipp

doi:10.1039/c3cp50930c

Cited by 264 publications

(391 citation statements)

References 39 publications

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“…X‐ray diffraction confirms that the cube‐shaped discharge product is NaO 2 (Figure S3, S4) in accord with many previous reports on similar cells 1b,1c, 2a,2b, 3a. After discharge or recharge to 2.8 and 3.65 V, 4.1, 4.3, and 7.2 %, respectively, of the DMA at the sample points ②, ③, and ④ was converted into DMA‐O 2 (Figure 1 b).…”

supporting

confidence: 91%

“…Previously it was reported that most parasitic chemistry occurs during discharge and less on charge 2a, 3a. Charging above around 3.5 V caused the number of O 2 per e − evolved to deviate more significantly from one than at lower voltages.…”

mentioning

confidence: 95%

“…During subsequent resting and charge, more of these side products form and typically the e − /O 2 ratio deviates by several percent from one 2a, 3c, 4b, 5. Although less side products form than in the Li–O 2 cell, cyclability is similarly poor: restricted capacity can often be maintained for up to hundreds of cycles albeit at the expense of true energy, but at full discharge cells fail within some 10 cycles and capacity fading becomes significantly worse with rising charge cut‐off voltage 1c, 2a,2c,2d, 3a,3d, 6…”

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confidence: 99%

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Singlet Oxygen during Cycling of the Aprotic Sodium–O₂ Battery

et al. 2017

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Aprotic sodium–O2 batteries require the reversible formation/dissolution of sodium superoxide (NaO2) on cycling. Poor cycle life has been associated with parasitic chemistry caused by the reactivity of electrolyte and electrode with NaO2, a strong nucleophile and base. Its reactivity can, however, not consistently explain the side reactions and irreversibility. Herein we show that singlet oxygen (1O2) forms at all stages of cycling and that it is a main driver for parasitic chemistry. It was detected in‐ and ex‐situ via a 1O2 trap that selectively and rapidly forms a stable adduct with 1O2. The 1O2 formation mechanism involves proton‐mediated superoxide disproportionation on discharge, rest, and charge below ca. 3.3 V, and direct electrochemical 1O2 evolution above ca. 3.3 V. Trace water, which is needed for high capacities also drives parasitic chemistry. Controlling the highly reactive singlet oxygen is thus crucial for achieving highly reversible cell operation.

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confidence: 91%

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Singlet Oxygen during Cycling of the Aprotic Sodium–O₂ Battery

et al. 2017

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“…The quantity of Li 2 O 2 formed was determined by ultraviolet-visible spectrometry (Thermo Evolution 200) using an ultraviolet-visible titration method reported previously 20,52 . The unwashed discharged electrode and separators were added to a vial containing a known amount of water; Li 2 O 2 reacts with water to produce H 2 O 2 in solution.…”

Section: Methodsmentioning

confidence: 99%

Erratum: Promoting solution phase discharge in Li–O2 batteries containing weakly solvating electrolyte solutions

Gao¹,

Chen²,

Johnson³

et al. 2016

Nature Mater

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On discharge, the Li-O 2 battery can form a Li 2 O 2 film on the cathode surface, leading to low capacities, low rates and early cell death, or it can form Li 2 O 2 particles in solution, leading to high capacities at relatively high rates and avoiding early cell death. Achieving discharge in solution is important and may be encouraged by the use of high donor or acceptor number solvents or salts that dissolve the T he high theoretical specific energy of the rechargeable Li-O 2 battery has generated intense interest in the possibility of a practical device that could deliver energy storage significantly in excess of today's lithium-ion batteries 1-9 . However, major challenges hinder the development of such a technology 1-6,10-14 . Typically a Li-O 2 battery is composed of a lithium metal anode separated by an aprotic electrolyte solution from a porous O 2 cathode. The reaction at the cathode involves, on discharge, the reduction of O 2 to form Li 2 O 2 , with oxidation of the latter on charge. Growth of Li 2 O 2 on the cathode surface leads to low capacities, poor rates and early cell death [15][16][17] . In contrast, if Li 2 O 2 can be induced to grow in the electrolyte solution then high discharge capacities at relatively high rates and avoiding early cell death is possible 15 . It is clearly important to operate a Li-O 2 battery in which Li 2 O 2 grows in solution.A number of groups have elucidated the mechanism of O 2 reduction to Li 2 O 2 on discharge 15,16,[18][19][20][21] . The reduction proceeds through the following general steps: 22,[27][28][29][30] . High donor number salts have been shown to increase the capacity fourfold and reduce the discharge overpotential by ∼30-50 mV over low donor number salts 22 . Viologens 27,28 , phthalocyanines 29 and quinones 30 have been investigated as possible soluble reduction catalysts. Although the studies of such catalysts are important, in most cases there is little or no direct evidence demonstrating that they promote formation of Li 2 O 2 in solution and not on the electrode surface because they rely on electrochemical measurements alone. Yet past work on Li-O 2 batteries has shown how essential it is to provide more than electrochemical evidence in this field 31 . In some cases, soluble catalysts show an increase in discharge voltage (lower overpotential) as small as, for example, 40 mV (refs 28,29), which is very unlikely to be sufficient to shut off the direct reduction of O 2 to Li 2 O 2 , essential to stop detrimental Li 2 O 2 film formation. Also, none of the previous studies in low donor number solvents exhibited a significant increase in capacity on discharge at a relatively high rate, which is important for a successful Li-O 2 battery.Here we demonstrate that addition of DBBQ (2,5-di-tert-butyl-1,4-benzoquinone) to a weakly solvating (low donor number) electrolyte solution, LiTFSI in ether 22 , promotes O 2 reduction to Li 2 O 2 in solution while halving the discharge overpotential (increasing the discharge potential), suppressing the growth of a Li 2...

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“…In a sodium-oxygen battery the Na metal of the anode reacts during discharge with (atmospheric) oxygen and may form different discharge products such as NaO 2 or Na 2 O 2 or Na 2 O 2 · 2 H 2 O [7,11,12]. Which product is finally formed depends on a number of influencing parameters such as the cell setup, the components used as well as the presence of water or other proton sources [7].…”

Section: Introductionmentioning

confidence: 99%