Insight into the Interfacial Process and Mechanism in Lithium–Sulfur Batteries: An In Situ AFM Study

Lang, Shuang‐Yan; Shi, Yang; Guo, Yu‐Guo; Wang, Dong; Wen, Rui; Li, Wan

doi:10.1002/anie.201608730

Cited by 127 publications

(86 citation statements)

References 32 publications

(34 reference statements)

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“…During the subsequent charge, the lamellar Li 2 S is completely dissolved and Li 2 S 2 nanoparticles remain on the surface. Li 2 S 2 is oxidized incompletely and is reversibly deposited upon cycling, revealing the fading mechanism in Li–S batteries . They also observe the interfacial behavior at high temperature (60 °C) in the same catholyte.…”

Section: Beyond Li‐ion Batteriesmentioning

confidence: 92%

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

Wang

Liu

Zhao

et al. 2018

Energy & Environ Materials

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The development of advanced lithium batteries represents a major technological challenge for the new century. Understanding the fundamental electrode degradation mechanisms is important for battery performance improvements. The complex electrochemical processes inside a working battery are being explored to a limited extent. Various advanced material characterization techniques have been used to monitor dynamic conditions for optimizing battery materials. State‐of‐the‐art atomic force microscopy methods have been applied to energy storage systems, specifically lithium‐ion batteries. Atomic force microscopy is an ideal tool to provide localized morphological, chemical, and physical information at nanoscale for the in‐depth understanding of the electrochemical processes, reaction mechanisms, and degradation of battery materials. Here, we review recent progress in the development and application of atomic force microscopy for high‐performance lithium‐ion batteries. We discuss atomic force microscopy as an analytical tool to help researchers understand graphite, silicon, layered metal oxides, and other representative electrode materials. We summarize the importance of atomic force microscopy technique in studying the next‐generation Li–S and Li–O2 batteries. We also highlight some of the remaining challenges and possible solutions for future development.

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Section: Beyond Li‐ion Batteriesmentioning

confidence: 92%

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

Wang

Liu

Zhao

et al. 2018

Energy & Environ Materials

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“…Li 2 S (99.98%), sulfur (S 8 Polytetrafluoroethylene preparation (PTFE dispersion, 60 wt% dispersion in H 2 O) and 2-propanol (anhydrous, 99.5%) were received from Sigma-Aldrich for the preparation of bulk sulfur cathode. Li 2 S (99.98%), sulfur (S 8 Polytetrafluoroethylene preparation (PTFE dispersion, 60 wt% dispersion in H 2 O) and 2-propanol (anhydrous, 99.5%) were received from Sigma-Aldrich for the preparation of bulk sulfur cathode.…”

Section: Methodsmentioning

confidence: 99%

“…[1c,2] Controlling electrochemical deposition of Li 2 S is a major challenge in lithium-sulfur batteries as premature Li 2 S passivation [1d,3] leads to low sulfur utilization and low rate capability. [6] The mechanism of Li 2 S deposition/growth and its dependence on electrode substrate have been extensively investigated via theoretical [7] and experimental approaches (scanning electron microscopy (SEM) imaging, [6a] atomic force microscopy (AFM) [8] ). [6] The mechanism of Li 2 S deposition/growth and its dependence on electrode substrate have been extensively investigated via theoretical [7] and experimental approaches (scanning electron microscopy (SEM) imaging, [6a] atomic force microscopy (AFM) [8] ).…”

Section: Introductionmentioning

confidence: 99%

Solvent‐Mediated Li₂S Electrodeposition: A Critical Manipulator in Lithium–Sulfur Batteries

Zhou

et al. 2018

Advanced Energy Materials

268

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such as silicene [9a] and ionic compounds [10a] were shown to speed up the Li 2 S lateral passivation rate, leading to lower capacities.Solvent has a strong impact on Li 2 S deposition. The kinetics and morphology of Li 2 S deposition in glyme-based polysulfide solutions was studied and a progressive nucleation and a 2D island growth model was proposed. [6a] In addition, the use of discharge mediator was reported to slow down the impingement of insulating Li 2 S islands on carbon and transform the 2D growth to a 3D growth. [11] This is in line with Cuisinier et al. [12] reporting a distinct Li 2 S deposition mechanism in electron pair donor electrolytes compared to glymes due to the partial solvation of Li 2 S and the additional chemical pathways provided by the increased stabilization of polysulfide radicals. Recently, Pan et al. [4] reported that solvents with medium donor number (DN) yield flower-like Li 2 S morphology, low-DN solvents make Li 2 S films, and high-DN solvents give rise small particles. These pioneering studies suggest that the solution mediation process plays a critical role in Li 2 S deposition and highlight the urgent need for developing quantitative and comprehensive correlation between solvent property and Li 2 S nucleation and growth.In this work, we establish structure-property relationship of solvent in controlling solid Li 2 S deposition and develop quantitative solvent-mediated Li 2 S growth models as guides to solvent selection. We investigate three solvent's properties and their roles on Li 2 S deposition: (1) the donicity which governs the stability of the polysulfide anions (i.e., the precursor of Li 2 S deposition) through (Li + ) sol -polysulfide interactions; [12,13] (2) the polarity (dielectric constant) which governs the solvation ability of the final product Li 2 S; [14] (3) the viscosity which strongly affects the diffusivity of polysulfide and dissolved Li 2 S. [15] We show that these solvent-controlled properties are essential factors pertaining to the sulfur utilization, electrode kinetics, and reversibility of electrochemical reduction of elemental sulfur. Finally, we demonstrate the effectiveness of the solvent selection criteria developed in this study in identifying new and more effective electrolytes for Li-S batteries. Results and DiscussionWe study Li 2 S deposition in electrolyte model systems of two major groups: (i) ether-based solvents: 1,2-dimethoxyethane (G1), diethylene glycol dimethyl ether (G2), triethylene glycol Controlling electrochemical deposition of lithium sulfide (Li 2 S) is a major challenge in lithium-sulfur batteries as premature Li 2 S passivation leads to low sulfur utilization and low rate capability. In this work, the solvent's roles in controlling solid Li 2 S deposition are revealed, and quantitative solventmediated Li 2 S growth models as guides to solvent selection are developed. It is shown that Li 2 S electrodeposition is controlled by electrode kinetics, Li 2 S solubility, and the diffusion of polysulfide/Li 2 S, which is dictated...

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“…It was therefore hypothesized that the surface coverage by Li 2 S, which is enhanced at larger polarizations, is the main limiting factor of the rate capability of Li-S cells. Lang et al 9 demonstrated a different Li 2 S morphology evolution behavior using in-situ AFM, where it was found that larger, lamellae structure of Li 2 S were formed at high discharge rate whereas smaller nanoparticles of Li 2 S 2 were formed during lower rate discharge. The experimental setup in both imaging studies, however, were not representative of a real Li-S battery that has much lower electrolyte-to-sulfur mass ratio.…”

mentioning

confidence: 99%

What Limits the Rate Capability of Li-S Batteries during Discharge: Charge Transfer or Mass Transfer?

Zhang

Marinescu

Waluś

et al. 2017

J. Electrochem. Soc.

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Li-S batteries exhibit poor rate capability under lean electrolyte conditions required for achieving high practical energy densities. In this contribution, we argue that the rate capability of commercially-viable Li-S batteries is mainly limited by mass transfer rather than charge transfer during discharge. We first present experimental evidence showing that the charge-transfer resistance of Li-S batteries and hence the cathode surface covered by Li 2 S are proportional to the state-of-charge (SoC) and not to the current, directly contradicting previous theories. We further demonstrate that the observed Li-S behaviors for different discharge rates are qualitatively captured by a zero-dimensional Li-S model with transport-limited reaction currents. This is the first Li-S model to also reproduce the characteristic overshoot in voltage at the beginning of charge, suggesting its cause is the increase in charge transfer resistance brought by Li 2 S precipitation. Achieving a high practical energy density in Li-S batteries requires increased sulfur loading and reduced electrolyte loading at cell level. However, increasing the sulfur-to-electrolyte mass ratio lowers the sulfur utilization as well as the rate capability.1-3 The charge rate of Li-S batteries is mainly limited by the large initial overpotential associated with the activation of precipitated Li 2 S, 4 as well as the slow subsequent dissolution that could lead to incomplete Li 2 S conversion at the end of charge. 5 The mechanisms behind the low discharge rate capability have been explained in terms of mass transport limitation and surface passivation caused by the accumulation of precipitated Li 2 S.The transport limitation could arise from high electrolyte viscosity and pore-blocking due to localized Li 2 S precipitation. We recently demonstrated that a Li-S cell discharged at high current can provide extra capacity after an hour of relaxation.6 With a one-dimensional Li-S model, it was found that slow ionic transport could force polysulfides to accumulate temporarily in the separator, leading to the known reduced capacity at high discharge rates. The capacity recovery phenomenon is the result of redistribution of polysulfides across the cell during relaxation. Danner et al. 7 further demonstrated with a multiscale Li-S model that localized precipitation tends to occur at the carbon-sulfur particle surface, leading to pore-blocking and transport-limited discharge capacity for high sulfur loading.The insulating and insoluble discharge product, Li 2 S, has been shown experimentally to cover active cathode surfaces during discharge and increase the charge-transfer resistance. The relation between discharge rate and morphology of the precipitate, however, remains under debate. Based on ex-situ SEM imaging of a carbon fiber ultramicroelectrode of a Li-S cell, Fan et al. 8 revealed that Li 2 S formed as a thin, continuous coating after a fast discharge but appeared as a small number of large particles after a slow discharge. It was therefore hypothesized that ...

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Insight into the Interfacial Process and Mechanism in Lithium–Sulfur Batteries: An In Situ AFM Study

Cited by 127 publications

References 32 publications

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

Solvent‐Mediated Li₂S Electrodeposition: A Critical Manipulator in Lithium–Sulfur Batteries

What Limits the Rate Capability of Li-S Batteries during Discharge: Charge Transfer or Mass Transfer?

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Insight into the Interfacial Process and Mechanism in Lithium–Sulfur Batteries: An In Situ AFM Study

Cited by 127 publications

References 32 publications

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

Solvent‐Mediated Li2S Electrodeposition: A Critical Manipulator in Lithium–Sulfur Batteries

What Limits the Rate Capability of Li-S Batteries during Discharge: Charge Transfer or Mass Transfer?

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Solvent‐Mediated Li₂S Electrodeposition: A Critical Manipulator in Lithium–Sulfur Batteries