Progress in Mechanistic Understanding and Characterization Techniques of Li‐S Batteries

Xu, Rui; Lü, Jun; Amine, Khalil

doi:10.1002/aenm.201500408

Cited by 436 publications

(352 citation statements)

References 204 publications

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“…Understanding their formation and conversion to Li 2 S requires studies under real-time conditions since with that we can avoid the artefacts from post treatment and we can get insight to the real working mechanism(s). 17 XAS provides details on oxidation state (XANES part of the spectrum) and atomic distribution (EXAFS part of the spectrum). Contributions of different sulfur compounds in the cathode (sulfur, Li-polysulfides with different chain lengths, Li 2 S) in the XANES spectra can be identified by characteristic energy positions and shape of the sulfur absorption edge and pre-edge resonances.…”

Section: Resultsmentioning

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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Section: Resultsmentioning

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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“…Table S3 summarizes the different poly(sulfide)s formed during discharge together with the corresponding voltage at which they are formed. [35][36][37][38] Upon discharge, S/ACF in 1M LiTFSI in DME/DOL as electrolyte shows a maximum in the range of 2.3-2.4 V, which correspond to long-chain poly(sulfide)s, i.e. Li 2 S 8 and Li 2 S 4 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Differences in Electrochemistry between Fibrous SPAN and Fibrous S/C Cathodes Relevant to Cycle Stability and Capacity

Warneke

Eusterholz

Zenn

et al. 2017

J. Electrochem. Soc.

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Two different Li/S cathodes are compared in terms of capacity (mA . h . g sulfur −1 ) and intermediates during discharge and charge. One cathode material is based on fibrous SPAN, a sulfur-containing material obtained via the thermal conversion of poly(acrylonitrile), PAN, in the presence of sulfur. In this material, sulfur is covalently bound to the polymeric backbone. The second cathode material is based on porous activated carbon fibers (ACFs) with elemental sulfur embedded inside the ACFs' micropores. Cyclic voltammetry clearly indicates different discharge and charge chemistry of the two materials. While S-containing ACFs show the expected redoxchemistry of sulfur, SPAN does not form long-chain polysulfides during discharge; instead, sulfide is chopped off the polymer-bound sulfur chains to directly form Li 2 S. The high reversibility of this process accounts for both the high cycle stability and capacity of SPAN-based cathode materials.

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“…Secondly, the model does not account for disproportionation/association reactions that are known to occur among polysulfide species. While such reactions have been under intense experimental investigations [38,39], the exact reaction mechanisms are still not established for Li-S cells. Lastly, the present model assumes simple phenomenological expressions for the change in tortuosity and effective surface area (Eqs.…”

Section: −mentioning

confidence: 99%

Modelling transport-limited discharge capacity of lithium-sulfur cells

Zhang

Marinescu

Waluś

et al. 2016

Electrochimica Acta

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Lithium-sulfur (Li-S) battery could bring a step-change in battery technology with a potential specific energy density of 500 -600 Wh/kg. A key challenge for further improving the specific energy-density of Li-S cells is to understand the mechanisms behind reduced sulfur utilisation at low electrolyte loadings and high discharge currents. While several Li-S models have been developed to explore the discharge mechanisms of Li-S cells, they so far fail to capture the discharge profiles at high currents. In this study, we propose that the slow ionic transport in concentrated electrolyte is limiting the rate capability of Li-S cells. This transport-limitation mechanism is demonstrated through a one-dimensional Li-S model which qualitatively captures the discharge capacities of a sulfolane-based Li-S cell at different currents. Furthermore, our model predicts that a discharged Li-S cell is able regain some capacity with a short period of relaxation. This capacity recovery phenomenon is validated experimentally for different discharge currents and relaxation durations. The transport-limited discharge behavior of Li-S cells highlights the importance of optimizing the electrolyte loading and electrolyte transport property in Li-S cells.

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Progress in Mechanistic Understanding and Characterization Techniques of Li‐S Batteries

Cited by 436 publications

References 204 publications

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

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

Differences in Electrochemistry between Fibrous SPAN and Fibrous S/C Cathodes Relevant to Cycle Stability and Capacity

Modelling transport-limited discharge capacity of lithium-sulfur cells

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