Insights into Li-S Battery Cathode Capacity Fading Mechanisms: Irreversible Oxidation of Active Mass during Cycling

Diao, Yan; Xie, Kai; Xiong, Shizhao; Hong, Xiaobin

doi:10.1149/2.020211jes

Cited by 238 publications

(215 citation statements)

References 24 publications

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“…As shown in Supplementary Fig. 4, the binding energy peaks around 160 eV of the S 2p spectra indicate the formation of Li x S on the electrodes after discharging to 1.7 V 35,36 . The Li 1s spectra ( Supplementary Fig.…”

Section: Resultsmentioning

confidence: 86%

Improving lithium–sulphur batteries through spatial control of sulphur species deposition on a hybrid electrode surface

et al. 2014

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Lithium-sulphur batteries are attractive owing to their high theoretical energy density and reasonable kinetics. Despite the success of trapping soluble polysulphides in a matrix with high surface area, spatial control of solid-state sulphur and lithium sulphide species deposition as a critical aspect has not been demonstrated. Herein, we show a clear visual evidence that these solid species deposit preferentially onto tin-doped indium oxide instead of carbon during electrochemical charge/discharge of soluble polysuphides. To incorporate this concept of spatial control into more practical battery electrodes, we further prepare carbon nanofibers with tin-doped indium oxide nanoparticles decorating the surface as hybrid three-dimensional electrodes to maximize the number of deposition sites. With 12.5 ml of 5 M Li 2 S 8 as the catholyte and a rate of C/5, we can reach the theoretical limit of Li 2 S 8 capacity B1,470 mAh g À 1 (sulphur weight) under the loading of hybrid electrode only at 4.3 mg cm À 2 .

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Section: Resultsmentioning

confidence: 86%

Improving lithium–sulphur batteries through spatial control of sulphur species deposition on a hybrid electrode surface

et al. 2014

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“…The sulfur spectra show small peaks coming from Li 2 S (S 2p 3/2 161.9 eV) and Li 2 S 2 (S 2p 3/2 163.4 eV), 33 indicating some irreversibility upon charge, and more intense peaks from SO 3 2− (S 2p 3/2 166.9 eV) and SO 4 2− (S 2p 3/2 168.9 eV), 37 due to reactions with nitrate in the electrolyte. 29,38 There is no visible sign of neutral sulfur, indicating that sulfur is not fully oxidized back to S 8 . The XPS peaks of C were the same as observed in the pristine cathode, with the caveat that the C=O peak was sharper, suggesting some reaction between C and the nitrate.…”

Section: Resultsmentioning

confidence: 99%

Radical Decomposition of Ether-Based Electrolytes for Li-S Batteries

Lodovico¹,

Varzi²,

Passerini³

2017

J. Electrochem. Soc.

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In this work, the stability of ether-based electrolytes for Li-S batteries is investigated with particular regard to the effect of dissolved oxygen. Specifically, the performance of two different electrolyte solvents, i.e., 1,2-dimethoxyethane and its mixture with 1,3-dioxolane (DME:DOL, 1:1 v/v), is characterized in cells assembled in dry air environment, which would substantially lower production costs with respect to inert atmosphere (Ar). Although stability of all the components would suggest that Li-S batteries built in both the environments should behave similarly, it is found that cells containing the DME:DOL-based electrolyte are rather unstable in the presence of O 2 in contrast to those employing DME-based electrolyte, which show a relatively good performance. The different sensitivity toward O 2 of these electrolytes is associated to the ring-opening reaction of DOL, which happens to a greater extent when O 2 is present, but occurs also in its absence. Based on these results a mechanism for electrolyte degradation in Li-S cells, and its reaction with dissolved polysulfides is proposed, which rationally explain for the first time the behavior already reported in literature for these kind of batteries. These findings are also relevant to the field of Li-O 2 batteries, where these ether-based electrolytes are also used. Sulfur has been extensively investigated as a new cathode material for secondary batteries, in order to replace metal oxides normally used in lithium-ion batteries (LIBs). The first point of interest is its high theoretical specific capacity, around 1672 mAh g −1 , but, as a raw material sulfur is also non-toxic, readily available, and very inexpensive. It is indeed one of the main side products of crude oil refining, with more than 60 million tons produced annually.1 Even the relatively low operating voltage of sulfur-based cathodes, at around 2 V vs. Li/Li + , can be considered as a potential advantage, making it intrinsically safer. 2 Furthermore, the high specific gravimetric capacity of sulfur enables the remarkable specific energy of about 2600 W h kg −1 . However, Lithium-Sulfur batteries (LSB) still present some specific challenges that need to be solved to enable their commercialization.2 First, sulfur has a very low electrical conductivity, around 5 × 10 −30 S cmat 25• C, requiring the introduction of a conductive matrix, normally carbon-based. The carbon host is generally electrochemically inert, such that it decreases the energy density of the electrode as whole, especially since it is often near to 50 wt% of the total sulfur-composite mass. Secondly, and most importantly, sulfur is a conversion material undergoing several chemical transformations during discharge and forming a variety of different polysulfides with the formal oxidation state of sulfur changing from 0 to −2. Some of these intermediate species are soluble in the electrolyte, and very reactive toward both the electrolyte itself 3,4 and the lithium metal anode. 2,5 Most importantly though, their dissolution cause...

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“…For example, the irreversible oxidation of low order polysulfides to higher order species at the cathode side can also lead to reduced kinetics and capacity fade due to loss of active material. 30 As this occurs at low voltages, an irreversible precipitation-related loss could account for the three cycling stages seen in experiments without attributing a strong negative effect to a slow recovery charge. The effect of other precipitation-related irreversibility, such as caused by details of the crystallization/nucleation and growth of the precipitated material, or changes to microstructure could also be explored.…”

Section: − *mentioning

confidence: 97%

Irreversible vs Reversible Capacity Fade of Lithium-Sulfur Batteries during Cycling: The Effects of Precipitation and Shuttle

Marinescu

O’Neill

Zhang

et al. 2017

J. Electrochem. Soc.

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Lithium-sulfur batteries could deliver significantly higher gravimetric energy density and lower cost than Li-ion batteries. Their mass adoption, however, depends on many factors, not least on attaining a predictive understanding of the mechanisms that determine their performance under realistic operational conditions, such as partial charge/discharge cycles. This work addresses a lack of such understanding by studying experimentally and theoretically the response to partial cycling. A lithium-sulfur model is used to analyze the mechanisms dictating the experimentally observed response to partial cycling. The zero-dimensional electrochemical model tracks the time evolution of sulfur species, accounting for two electrochemical reactions, one precipitation/dissolution reaction with nucleation, and shuttle, allowing direct access to the true cell state of charge. The experimentally observed voltage drift is predicted by the model as a result of the interplay between shuttle and the dissolution bottleneck. Other features are shown to be caused by capacity fade. We propose a model of irreversible sulfur loss associated with shuttle, such as caused by reactions on the anode. We find a reversible and an irreversible contribution to the observed capacity fade, and verify experimentally that the reversible component, caused by the dissolution bottleneck, can be recovered through slow charging. This model can be the basis for cycling parameters optimization, or for identifying degradation mechanisms relevant in applications. Lithium sulfur (LiS) batteries have the potential to provide a step change in performance, compared to Li-ion batteries, with an expected practical energy density of 700 Wh kg −1 compared to that of the intercalation Li-ion batteries, of 210 Wh kg −1 . 1,2 Added benefits, such as a potential low cost due to the abundance of the active materials, low toxicity and relative safety, 3 make them an attractive energy storage solution for a wide variety of applications, such as space exploration 4 and low temperature energy delivery. 5 However, the relatively low power capabilities, significant self discharge and low cycle life have so far hindered mainstream adoption of LiS cells. Degradation mechanisms such as lithium anode corrosion, self discharge and low coulombic efficiency have all been related to the polysulfide shuttle. As a result, most effort in the research community is currently directed toward decreasing the amount of shuttle through material design, and assessing the properties of the proposed materials through coin cell characterization.We argue that equally important for accelerating the adoption of this battery chemistry is the understanding of how real cells behave under real operating conditions, which often include incomplete charge/discharge cycles, noisy current loads and rest periods at various states of charge (SoC). Understanding and detecting the mechanisms leading to degradation, such as capacity fade, are intermediate steps crucial to predicting cycle life. Such understanding can...

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Insights into Li-S Battery Cathode Capacity Fading Mechanisms: Irreversible Oxidation of Active Mass during Cycling

Cited by 238 publications

References 24 publications

Improving lithium–sulphur batteries through spatial control of sulphur species deposition on a hybrid electrode surface

Improving lithium–sulphur batteries through spatial control of sulphur species deposition on a hybrid electrode surface

Radical Decomposition of Ether-Based Electrolytes for Li-S Batteries

Irreversible vs Reversible Capacity Fade of Lithium-Sulfur Batteries during Cycling: The Effects of Precipitation and Shuttle

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