On the Way Toward Understanding Solution Chemistry of Lithium Polysulfides for High Energy Li–S Redox Flow Batteries

Pan, Huilin; Wei, Xiaoliang; Henderson, Wesley A.; Shao, Yuyan; Chen, Junzheng; Bhattacharya, Priyanka; Xiao, Jie

doi:10.1002/aenm.201500113

Cited by 162 publications

(173 citation statements)

References 44 publications

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1 M lithium bis(trifl uoromethanesulfonyl)imide (LiTFSI) in 1,3-dioxolane/1,2-dimethoxyethane (DOL/DME). [ 22,23 ] Alternative cell designs incorporating solid-state electrolytes completely prevent the dissolution of polysulfi des, but the utilization of the sulfur (i.e., the reversible capacity) is also largely reduced. [ 22,23 ] Alternative cell designs incorporating solid-state electrolytes completely prevent the dissolution of polysulfi des, but the utilization of the sulfur (i.e., the reversible capacity) is also largely reduced.

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confidence: 99%

Restricting the Solubility of Polysulfides in Li‐S Batteries Via Electrolyte Salt Selection

Chen

Han

Henderson

et al. 2016

Advanced Energy Materials

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1 M lithium bis(trifl uoromethanesulfonyl)imide (LiTFSI) in 1,3-dioxolane/1,2-dimethoxyethane (DOL/DME). [ 21 ] Switching to other solvents with high dielectric constant such as dimethyl sulfoxide (DMSO) or dimethylacetamide (DMA) facilitates the production of sulfur radicals and the full utilization of the sulfur, but the cycling stability of the cell is also sacrifi ced and the unstable interface between the reactive DMSO/DMA solvent and Li metal raises other concerns. [ 22,23 ] Alternative cell designs incorporating solid-state electrolytes completely prevent the dissolution of polysulfi des, but the utilization of the sulfur (i.e., the reversible capacity) is also largely reduced. [ 24 ] Therefore, the solubility of the polysulfi des in cells with liquid electrolytes needs to be carefully tuned and well understood. In most studies, a low sulfur loading (less than 1 mg cm -2 ) is used, but a high S loading is desired for high-capacity full cells. [ 25,26 ] In this paper, lithium trifl uoromethyl-4,5-dicyanoimidazole (LiTDI) is studied for Li-S cells. We study the effect of LiTDI on the solubility of polysulfi des. The performance of this electrolyte was investigated with a high sulfur (i.e., practically usable) loading at 3 mg cm -2 under a high current density.A comparison of the physical properties of electrolytes with either 1 M LiTFSI or LiTDI in DOL/DME (1/1, v/v) is shown in Table 1 . Both electrolytes have a comparable conductivity and viscosity, suitable for the electrochemical needs, but an 83% decrease in the Li 2 S 8 solubility is observed in the LiTDI electrolyte. Restricting the polysulfi de solubility to a low level is expected to improve the Li-S cell cycle life because of the suppression of the polysulfi de shuttle mechanism, reduction of anode contamination, and the minimization of the loss of active material from the cathode. [ 22 ] To understand the relationship between the polysulfi de solubility and electrolyte supporting salt, 7 Li and 17 O nuclear magnetic resonance (NMR) spectroscopic measurements were used to aid in understanding the solvation interactions. The δ ( 7 Li) for the LiTDI and LiTFSI-based electrolytes without polysulfi des was -0.8 and -1.2 ppm (relative to Li + cations fully solvated by H 2 O molecules) ( Figure 1 a-c), respectively. The δ ( 17 O) for the DME molecules shifts to ≈ -27.7 and -26.9 ppm in the LiTDI and LiTFSI-based electrolytes, respectively, from -24.3 ppm in a neat DOL/DME solvent mixture. The δ ( 17 O) for the DOL molecules near 35 ppm shifts by 1-2 ppm. The smaller shift of δ ( 17 O) for the DOL molecules relative to the DME molecules and signifi cant broadening of the peaks for the latter suggest that the Li + cations may be preferentially solvated by the DME. [ 27 ] It has been reported that the solvation of Li + cations in the electrolyte affects the short-chain polysulfi de solubility by solvating the Li + ion in the polysulfi des, but it did not affect the

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confidence: 99%

Restricting the Solubility of Polysulfides in Li‐S Batteries Via Electrolyte Salt Selection

Chen

Han

Henderson

et al. 2016

Advanced Energy Materials

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“…This has been elaborately described by Pan et al [81,82] in their Li-S redox flow battery system. This has been elaborately described by Pan et al [81,82] in their Li-S redox flow battery system.…”

Section: Salts For the Li/s Systemmentioning

confidence: 89%

Section: Carbonate-based Electrolyte With a Short-chain Sulfur-based mentioning

confidence: 99%

Structure–Property Relationships of Organic Electrolytes and Their Effects on Li/S Battery Performance

et al. 2017

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Electrolytes, which are a key component in electrochemical devices, transport ions between the sulfur/carbon composite cathode and the lithium anode in lithium-sulfur batteries (LSBs). The performance of a LSB mostly depends on the electrolyte due to the dissolution of polysulfides into the electrolyte, along with the formation of a solid-electrolyte interphase. The selection of the electrolyte and its functionality during charging and discharging is intricate and involves multiple reactions and processes. The selection of the proper electrolyte, including solvents and salts, for LSBs strongly depends on its physical and chemical properties, which is heavily controlled by its molecular structure. In this review, the fundamental properties of organic electrolytes for LSBs are presented, and an attempt is made to determine the relationship between the molecular structure and the properties of common organic electrolytes, along with their effects on the LSB performance.

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“…Li-PS RFBs have been reported where the operating voltage maintains the sulfur species always as the soluble Li 2 S 8 and Li 2 S 4 PS species. 119,128,228 Functioning like a conventional RFB, this Li-PS RFB only operates within the voltage window of the soluble PSs, and thus the theoretical capacity drops to 418 mA h g…”

Section: Lithium-ion Cathode Materialsmentioning

confidence: 99%

Review Article: Flow battery systems with solid electroactive materials

Koenig

2017

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Energy storage is increasingly important for a diversity of applications. Batteries can be used to store solar or wind energy providing power when the Sun is not shining or wind speed is insufficient to meet power demands. For large scale energy storage, solutions that are both economically and environmentally friendly are limited. Flow batteries are a type of battery technology which is not as well-known as the types of batteries used for consumer electronics, but they provide potential opportunities for large scale energy storage. These batteries have electrochemical recharging capabilities without emissions as is the case for other rechargeable battery technologies; however, with flow batteries, the power and energy are decoupled which is more similar to the operation of fuel cells. This decoupling provides the flexibility of independently designing the power output unit and energy storage unit, which can provide cost and time advantages and simplify future upgrades to the battery systems. One major challenge of the existing commercial flow battery technologies is their limited energy density due to the solubility limits of the electroactive species. Improvements to the energy density of flow batteries would reduce their installed footprint, transportation costs, and installation costs and may open up new applications. This review will discuss the background, current progress, and future directions of one unique class of flow batteries that attempt to improve on the energy density of flow batteries by switching to solid electroactive materials, rather than dissolved redox compounds, to provide the electrochemical energy storage.

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On the Way Toward Understanding Solution Chemistry of Lithium Polysulfides for High Energy Li–S Redox Flow Batteries

Cited by 162 publications

References 44 publications

Restricting the Solubility of Polysulfides in Li‐S Batteries Via Electrolyte Salt Selection

Restricting the Solubility of Polysulfides in Li‐S Batteries Via Electrolyte Salt Selection

Structure–Property Relationships of Organic Electrolytes and Their Effects on Li/S Battery Performance

Review Article: Flow battery systems with solid electroactive materials

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