Electrochemical verification of the redox mechanism of FeS2 in a rechargeable lithium battery

Zhang, Sheng S.; Tran, Dat T.

doi:10.1016/j.electacta.2015.07.096

Cited by 43 publications

(34 citation statements)

References 30 publications

(40 reference statements)

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“…The S and FeS are generated from the decomposition of Li 2-x FeS 2 (x > 0.8) during further delithiation, which is not reversible at room temperature. 21 However, there has been evidence that FeS coming from FeS 2 recharge is covered by FeS 2 surface layer, 20 so the polysulfide adsorption capability should still be partially retained. The first discharge/charge voltage profile of S-FeS 2 composite electrode is shown in Figure 2 at 0.2C discharge rate, also shown is the sulfur electrode with similar sulfur loading (0.9 mg cm −2 ) as a reference.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, there has also been experimental evidence that FeS might be partially oxidized by polysulfide during the recharge and form FeS 2 surface layer on the FeS particles. 20 It can be imagined that the concentration of polysulfides and their oxidizing power should be even higher in S-FeS 2 composite electrodes than pure FeS 2 electrodes during cycling, so the chances of converting FeS to FeS 2 coated FeS should be even higher. The FeS 2 coated FeS might have a similar effect in adsorbing polysulfide in the later cycles of the S-FeS 2 electrode.…”

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confidence: 99%

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Interaction of FeS₂and Sulfur in Li-S Battery System

Sun

Cama

DeMayo

et al. 2016

J. Electrochem. Soc.

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Many transition metal sulfides are electronically conductive, electrochemically active and reversible in reactions with lithium. However, the application of transition metal sulfides as sulfur cathode additives in lithium-sulfur (Li-S) batteries has not been fully explored. In this study, Pyrite (FeS 2 ) is studied as a capacity contributing conductive additive in sulfur cathode for Li-S batteries. Electrochemically discharging the S-FeS 2 composite electrodes to 1.0 V activates the FeS 2 component, contributing to the improved Li-S cell discharge energy density. However, direct activation of the FeS 2 component in a fresh S-FeS 2 cell results in a significant shuttling effect in the subsequent charging process, preventing further cell cycling. The slight FeS 2 solubility in electrolyte and its activation alone in S-FeS 2 cells are not the root causes of the severe shuttling effect. The observed severe shuttling effect is strongly correlated to the 1 st charging of the activated S-FeS 2 electrode that promotes iron dissolution in electrolyte and the deposition of electronically conductive FeS on the anode SEI. Pre-cycling of the S-FeS 2 cell prior to the FeS 2 activation or the use of LiNO 3 electrolyte additive help to prevent the severe shuttling effect and allow the cell to cycle between 2.6 V to 1.0 V with an extra capacity contribution from the FeS 2 components. However, a more effective method of anode pre-passivation is still needed to fully protect the lithium surface from FeS deposition and allow the S-FeS 2 electrode to maintain high energy density over extended cycles. A mechanism explaining the observed phenomena based on the experimental data is proposed and discussed.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Interaction of FeS₂and Sulfur in Li-S Battery System

Sun

Cama

DeMayo

et al. 2016

J. Electrochem. Soc.

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“…[29][30][31][32][33][34] In contrast, while the synthesis of hollow MnS spheres for battery applications has been demonstrated, we are unaware of any reports of stable Li x MnS y -type species. Li x FeS 2 (with x between 0.5 and 2) has been identified in numerous studies using iron sulfide as a battery active material.…”

Section: Doi: 101002/aenm201701122mentioning

confidence: 99%

“…[40] Li x FeS 2 , on the other hand, participates in electrochemical oxidation and reduction reactions above 1.8 V versus Li/Li + , [29][30][31][32][33][34] and thus would be expected to react within the cycling window employed for the LiS batteries in this study (1.8-3.4 V vs Li/Li + ). MnS has been shown not to reduce above 0.7 V versus Li/Li + in studies of its use as a battery material.…”

Section: Doi: 101002/aenm201701122mentioning

confidence: 99%

An Effective Lithium Sulfide Encapsulation Strategy for Stable Lithium–Sulfur Batteries

Klein

Dolocan

et al. 2017

Advanced Energy Materials

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attributed to the insulating nature of sulfur and its discharge product, Li 2 S; (ii) fast capacity decay due to activematerial loss in the form of soluble polysulfide species; and (iii) potential safety hazards arising with the use of lithium metal as an anode.To mitigate the safety concerns of metallic lithium, one approach is to start with Li 2 S and couple it with a lithium-free anode (silicon, tin, or graphite). [14] When employed as a cathode, Li 2 S encounters less volume expansion in the first cycle; however, similar to its sulfur cathode counterpart, it also requires efficient electron transport pathways around the insulating Li 2 S particles and an effective encapsulation to reduce polysulfide dissolution. [15] In 2014, Seh et al. performed pioneering work that successfully encapsulated Li 2 S with a nanocomposite strategy consisting of 2D layered transition-metal disulfides that offered high conductivity and affinity for polysulfides. [16] The nanocomposite cathodes exhibited enhanced activity in LiS batteries as revealed by a lower charging overpotential, and improved cycling stability up to 400 cycles. However, the process utilized nanosized Li 2 S particles and a complex processing scheme requiring hightemperature annealing of the reacted product, among other preparation steps. In addition, hierarchical carbon structures have also been used to encapsulate Li 2 S forming nanocomposites; [17,18] however, their long-term cycling stability remains a concern considering the nonpolar nature of carbon and its lower affinity for polysulfide species with high polarity. [19,20] To date, a low-cost design of a stable, conductive encapsulation architecture for Li 2 S is yet to be realized.In this work, we build an encapsulation layer comprised of transition-metal sulfide on the surface of Li 2 S bulk particles via a facile strategy employing a surface chemical reaction between Li 2 S and an electrolyte additive containing the transition-metal salt. It is demonstrated that the surface ionization energy of the encapsulation layer determines the initial charging overpotential of Li 2 S. Moreover, while most additives generate encapsulation layers in the open-circuit configuration that are unstable during cycling, it is shown that at least one transition-metal additive, containing manganese, forms a stable encapsulation layer consisting of MnS via a chemical reaction with Li 2 S. The stability of such an in-situ-formed encapsulation layer is a result of the MnS compound being chemically inactive within the cycling window. Through this mechanistic analysis, we With a high theoretical capacity of 1162 mA h g −1 , Li 2 S is a promising cathode that can couple with silicon, tin, or graphite anodes for next-generation energy storage devices. Unfortunately, Li 2 S is highly insulating, exhibits large charge overpotential, and suffers from active-material loss as soluble polysulfides during battery cycling. To date, low-cost, scalable synthesis of an electrochemically active Li 2 S cathode remains a challenge. This work ...

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“…In other words, upon the first discharge the Li/FeS 2 battery turns to the combination of a Li/FeS cell and a Li/S cell. 1,21,36 In addition, we noticed that the Li anode plays an even more important role in affecting the cycle life of Li/FeS 2 cells. Based on our new insight into the redox mechanism, in this paper we analyze the capacity fading mechanism of Li/FeS 2 cells and demonstrate three facile strategies for improving the cyclability of Li/FeS 2 cells.…”

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confidence: 93%

Mechanism and Solution for the Capacity Fading of Li/FeS₂Battery

Zhang

Tran

2016

J. Electrochem. Soc.

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Development of Li/FeS 2 rechargeable batteries has been hampered by their short cycle life. In this paper, we start with the fundamental chemistry of FeS 2 in a non-aqueous liquid electrolyte to analyze the capacity fading mechanism of Li/FeS 2 batteries and propose three facile strategies for stabilizing capacity. It is repeatedly observed that the capacity fading of Li/FeS 2 cells follows a general mode consisting of a fast fading stage as Region 1, a slow fading stage as Region 2, and an accelerated fading stage as Region 3. We found that Region 1 is mainly attributed to the dissolution of lithium polysulfide leading to the loss of sulfur active material, and that Region 3 is mainly associated with the poor morphology of Li deposition resulting in the localized electric circuit shortening. The powder-like, small and loose Li particles not only react with electrolyte solvents drying-out the cell but also penetrate across the separator shortening the cell. Based on the above finding, the cycle life of Li/FeS 2 cells was improved by adding vinylene carbonate as the electrolyte additive, increasing mechanical pressure between two electrodes, and placing a carbon interlayer between the FeS 2 cathode and separator, respectively.

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Electrochemical verification of the redox mechanism of FeS2 in a rechargeable lithium battery

Cited by 43 publications

References 30 publications

Interaction of FeS₂and Sulfur in Li-S Battery System

Interaction of FeS₂and Sulfur in Li-S Battery System

An Effective Lithium Sulfide Encapsulation Strategy for Stable Lithium–Sulfur Batteries

Mechanism and Solution for the Capacity Fading of Li/FeS₂Battery

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Electrochemical verification of the redox mechanism of FeS2 in a rechargeable lithium battery

Cited by 43 publications

References 30 publications

Interaction of FeS2and Sulfur in Li-S Battery System

Interaction of FeS2and Sulfur in Li-S Battery System

An Effective Lithium Sulfide Encapsulation Strategy for Stable Lithium–Sulfur Batteries

Mechanism and Solution for the Capacity Fading of Li/FeS2Battery

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Interaction of FeS₂and Sulfur in Li-S Battery System

Interaction of FeS₂and Sulfur in Li-S Battery System

Mechanism and Solution for the Capacity Fading of Li/FeS₂Battery