Li‐S Battery Analyzed by UV/Vis in Operando Mode

Patel, Mrinali; Demir‐Cakan, Rezan; Morcrette, Mathieu; Tarascon, Jean‐Marie; Gaberšček, Miran; Dominko, Robert

doi:10.1002/cssc.201300142

Cited by 259 publications

(274 citation statements)

References 15 publications

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“…Despite these advantages, many challenges have to be overcome in its commercialization, such as the poor utilization and huge volume change (80%) of sulfur and its slow reaction kinetics. Highly soluble intermediate lithium polysulfides (LiPSs) are formed during the cycling which are dissolved into the electrolyte and some LiPSs shuttle from the cathode to the anode to form non‐reusable solid Li 2 S 2 /Li 2 S 2, 3. This leads to a continuous loss of active material, passivation of the anode, and low coulombic efficiency, and thus, it is considered to be one of the key issues limiting the practical use of Li–S batteries 4.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Effects in Lithium–Sulfur Batteries: Promoted Sulfur Transformation and Reduced Shuttle Effect

et al. 2017

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Lithium–sulfur (Li–S) battery has emerged as one of the most promising next‐generation energy‐storage systems. However, the shuttle effect greatly reduces the battery cycle life and sulfur utilization, which is great deterrent to its practical use. This paper reviews the tremendous efforts that are made to find a remedy for this problem, mostly through physical or chemical confinement of the lithium polysulfides (LiPSs). Intrinsically, this “confinement” has a relatively limited effect on improving the battery performance because in most cases, the LiPSs are “passively” blocked and cannot be reused. Thus, this strategy becomes less effective with a high sulfur loading and ultralong cycling. A more “positive” method that not only traps but also increases the subsequent conversion of LiPSs back to lithium sulfides is urgently needed to fundamentally solve the shuttle effect. Here, recent advances on catalytic effects in increasing the rate of conversion of soluble long‐chain LiPSs to insoluble short‐chain Li2S2/Li2S, and vice versa, are reviewed, and the roles of noble metals, metal oxides, metal sulfides, metal nitrides, and some metal‐free materials in this process are highlighted. Challenges and potential solutions for the design of catalytic cathodes and interlayers in Li–S battery are discussed in detail.

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Section: Introductionmentioning

confidence: 99%

Catalytic Effects in Lithium–Sulfur Batteries: Promoted Sulfur Transformation and Reduced Shuttle Effect

et al. 2017

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“…27,28 The latter has demonstrated to be a useful technique for qualitative and quantitative detection of polysulfides in the separator (detection of polysulfides which diffuse/migrate out from the cathode composite). In several of our works 22,27,28 we highlighted the sensitivity of the UV-VIS analytical technique, showing that it offers hints about the polysulfide formation mechanism which occurs in the bulk of the cathode. However, this spectroscopic tool for the study of polysulfide mechanism is based on the prediction that polysulfides are soluble into the electrolyte.…”

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confidence: 99%

Polysulfides Formation in Different Electrolytes from the Perspective of X-ray Absorption Spectroscopy

Dominko

Vižintin

Aquilanti

et al. 2017

J. Electrochem. Soc.

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Li-S batteries are promising energy storage technology for the future, however there two major problems remained which need to be solved before successful commercialization. Capacity fading due to polysulfide shuttle and corrosion of lithium metal are directly connected with the type and quantity of electrolyte used in the cells. Several recent works show dependence of the electrochemical behavior of Li-S batteries on type of the electrolyte. In this work we compare and discuss a discharge mechanism of sulfur conversion in three different electrolytes based on measurements with sulfur K-edge XAS. The sulfur conversion mechanism in the ether based electrolytes, the most studied type of solvents in the Li-S batteries, which are enabling high solubility of polysulfides are compared with the fluorinated ether based electrolytes with a reduced polysulfide solubility and in carbonate based electrolytes with the sulfur confined into a ultramicroporous carbon. In all three cases the sulfur reduction proceeds through polysulfide intermediate phases with a difference on the type polysulfides detected at different steps of discharge. Electrification of road transport has increased the pressure on materials' scientists to improve performance of the current Li-ion batteries and to develop new advanced high energy battery technologies. 1Among several post lithium-ion technologies, the lithium sulfur (Li-S) batteries are recognized as the most promising for commercialization in the near future. A combination of lithium and sulfur in the electrochemical cell corresponds to the theoretical energy density of 2600 Wh/kg, while the maximum practically accessible energy density is predicted to be close to 600 Wh/kg.2,3 This is much higher compared to Li-ion batteries and besides that, sulfur is inexpensive and naturally abundant. Nevertheless, problems related to the solubility of polysulfides in the electrolyte and the related redox shuttle phenomena cause short cycle life, potential safety problems, poor cycling efficiency, and relative fast self-discharge. Additional problems of Li-S batteries are very low electronic conductivity of the both end members in the discharge and charge process (i.e. sulfur and Li 2 S) and extensive corrosion of the metal lithium anode.Different directions how to improve Li-S battery cycle life have been explored, like synthesis of the optimized porous host matrices with active sites for polysulfide anchoring, 4,5 design and optimization of separators which can effectively suppress polysulfide cross communication between electrodes 6,7 and protection of lithium by artificial SEI 8 or by additives. 9 While most of the research was performed in the binary mixture of solvents using alkyl ethers (glymes) and heterocyclic acetyl (dioxolane), less attention has been paid to the development of new electrolytes for Li-S batteries. 10 Reasons for that are nested in the requirements which should be fulfilled in the development of new formulations. First of all, electrolytes used in the electrochemical cells must...

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“…[6][7][8][9] Many previous studies have used spectroscopic methods to determine the nature of the several polysulfides that may be found in solution during discharge from S 8 to Li 2 S and the reverse charge reaction. [7][8][9][10][11][12] By contrast, the contribution to the understanding of lithiumsulfur batteries that is made here is a purely thermodynamic treatment based on the equilibrium between three phases: solid S 8 , solid Li 2 S, and a solution of polysulfides in the electrolyte. 13,14 For simplicity, we do not consider the existence of any other solids such as Li 2 S 2 , which is often suggested as a reaction intermediate, despite the fact that no crystal structure has been published.…”

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confidence: 99%

Predicting the composition and formation of solid products in lithium–sulfur batteries by using an experimental phase diagram

et al. 2016

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The lithium-sulfur rechargeable battery has been studied intensively as a candidate for the high specific energy market, which has applications in electric vehicles, portable devices and grid energy storage. [1][2][3][4][5] The theoretical specific energy is ca., which is notably higher than the lithium-ion battery. Several other advantages of using sulfur as the positive electrode include its abundance, low cost and nontoxicity. The theoretical specific capacity of sulfur (1672 A h kg The reduction of S 8 to Li 2 S and reverse oxidation occur via multistep reaction pathways, which have led to the discharge and charge mechanisms being poorly understood compared with those of the lithium-ion battery. 6-9 Many previous studies have used spectroscopic methods to determine the nature of the several polysulfides that may be found in solution during discharge from S 8 to Li 2 S and the reverse charge reaction. 7-12By contrast, the contribution to the understanding of lithiumsulfur batteries that is made here is a purely thermodynamic treatment based on the equilibrium between three phases: solid S 8 , solid Li 2 S, and a solution of polysulfides in the electrolyte. 13,14 For simplicity, we do not consider the existence of any other solids such as Li 2 S 2 , which is often suggested as a reaction intermediate, despite the fact that no crystal structure has been published. Only one publication suggested a ternary S 8 -Li 2 S-electrolyte phase diagram, 9 but it was not supported by experimental data. Here we report the first experimental phase diagram of the S 8 -Li 2 S-electrolyte system and apply it to explain the changes in electrolyte composition during the slow discharge and charge of lithiumsulfur batteries. We show that the phase diagram provides fundamental information about the thermodynamic equilibrium, which is a good approximation for slow cycling rates, and an essential starting point to study the kinetics at faster rates. Figure 1 illustrates the general form of the S 8 -Li 2 Selectrolyte phase diagram. The edges represent the binary mole fractions, x i of each component, so that the bottom edge is related to the stoichiometry of Li 2 S n as follows:At the top of the diagram we find the one phase region where all the sulfur and Li 2 S will dissolve forming a polysulfide solution. Next, we find two, two-phase regions representing the saturated solutions of each respective solid (sulfur + solution and Li 2 S + solution, respectively); the curved upper boundaries show how the solubility of one solute increases with the concentration of the other. For example, starting from the saturated solution of sulfur in the pure solvent at point A, we follow a downward curve showing how adding lithium sulfide in solution increases the solubility of sulfur by reacting to form soluble polysulfides; similarly, point B signifies the solubility of lithium sulfide in pure solvent, and it increases with the addition of sulfur into the solution due to formation of different polysulfides. The two curves meet at point C, the

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Li‐S Battery Analyzed by UV/Vis in Operando Mode

Cited by 259 publications

References 15 publications

Catalytic Effects in Lithium–Sulfur Batteries: Promoted Sulfur Transformation and Reduced Shuttle Effect

Catalytic Effects in Lithium–Sulfur Batteries: Promoted Sulfur Transformation and Reduced Shuttle Effect

Polysulfides Formation in Different Electrolytes from the Perspective of X-ray Absorption Spectroscopy

Predicting the composition and formation of solid products in lithium–sulfur batteries by using an experimental phase diagram

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