Solvent Effect of Room Temperature Ionic Liquids on Electrochemical Reactions in Lithium–Sulfur Batteries

Park, Jun‐Woo; Yamauchi, Kento; Takashima, Eriko; Tachikawa, Naoki; Ueno, Kazuhide; Dokko, Kaoru; Watanabe, Masayoshi

doi:10.1021/jp400153m

Cited by 193 publications

(219 citation statements)

References 84 publications

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“…A constant current (0.1C) was applied as short pulses, between which the system was allowed to relax to quasiequilibrium (Materials and Methods). Remarkably, a reversible capacity close to the theoretical value of sulfur (1,667 mAh·g −1 ) was achieved during the first cycle under this quasi-equilibrium condition, which cannot be achieved in nonaqueous systems (32,33). Moreover, the gap between the potential at the end of each pulse (polarization potential, as indicated by the black line in Fig.…”

Section: Resultsmentioning

confidence: 62%

Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility

Yang

Suo

Borodin

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

177

182

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Leveraging the most recent success in expanding the electrochemical stability window of aqueous electrolytes, in this work we create a unique Li-ion/sulfur chemistry of both high energy density and safety. We show that in the superconcentrated aqueous electrolyte, lithiation of sulfur experiences phase change from a highorder polysulfide to low-order polysulfides through solid-liquid two-phase reaction pathway, where the liquid polysulfide phase in the sulfide electrode is thermodynamically phase-separated from the superconcentrated aqueous electrolyte. The sulfur with solid-liquid two-phase exhibits a reversible capacity of 1,327 mAh/(g of S), along with fast reaction kinetics and negligible polysulfide dissolution. By coupling a sulfur anode with different Li-ion cathode materials, the aqueous Li-ion/sulfur full cell delivers record-high energy densities up to 200 Wh/(kg of total electrode mass) for >1,000 cycles at ∼100% coulombic efficiency. These performances already approach that of commercial lithium-ion batteries (LIBs) using a nonaqueous electrolyte, along with intrinsic safety not possessed by the latter. The excellent performance of this aqueous battery chemistry significantly promotes the practical possibility of aqueous LIBs in large-format applications.water-in-salt | rechargeable aqueous battery | aqueous sulfur battery | gel polymer electrolyte | phase separation I n the past two decades, rechargeable lithium-ion batteries (LIBs) have revolutionized consumer electronics with their high energy density and excellent cycling stability, and are the state-of-the-art candidates for applications ranging from kilowatt hours for electric vehicles up to megawatt hours for grids (1, 2). The latter applications in large-format present much more stringent requirements for safety, cost, and environmental friendliness, besides energy density and cycle life. The shortcomings of LIB are mostly due to the flammable and toxic nonaqueous electrolytes and moderate energy densities (<400 Wh·kg −1 ) provided by the electrochemical couples currently used (3). Among the various "beyond Li-ion" high-energy chemistries (>500 Wh·kg −1 ) explored currently, the nonaqueous lithium/sulfur (Li/S) battery based on sulfur as a cathode (theoretical capacity of 1,675 mAh·g −1 ) and metallic lithium as an anode seems to be the most practical, as evidenced by the mushrooming literature and significant advances in this system in the past 5 y (4-7). However, commercialization of this system still faces challenges because of severe safety concerns associated with the dendrite growth of metallic Li anode in highly inflammable ether-based electrolytes (8), and the high self-discharge associated with parasitic shuttling of the intermediate polysulfide species. Moreover, the moisture-sensitive nature of the nonaqueous electrolyte would contribute significantly to the cost of the Li/S battery pack due to the stringent moisture-exclusion infrastructure required during the manufacturing, processing, and packaging of the cells. The indispensabl...

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Section: Resultsmentioning

confidence: 62%

Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility

Yang

Suo

Borodin

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

177

182

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“…117,122 Consequently, solvate ILs are suitable for use as electrolytes in lithium ion batteries [111][112][113][114] and lithium-sulfur batteries. [115][116][117][118][119][120] The most striking and significant findings of our research on solvate ILs are the formation criteria of solvate ILs, 101 the enhanced oxidation stability of coordinating solvents, 95 the low coordinating properties of solvate cations and anions, and their electrode reactions with graphite. 121,122 Figure 8 shows how the anionic structures of lithium salts affect the formation of solvate ILs.…”

Section: © -Conducting Ils and Solvate Ilsmentioning

confidence: 80%

“…[115][116][117][118][119][120] The theoretical capacity of the S cathode is ten times greater than that of conventional cathode materials used in current Li-ion batteries. However, Li-S batteries suffer from the dissolution of lithium polysulfides, which are formed by the redox reactions at the S cathode.…”

Section: © -Conducting Ils and Solvate Ilsmentioning

confidence: 99%

Design and Materialization of Ionic Liquids Based on an Understanding of Their Fundamental Properties

Watanabe

2016

Electrochemistry

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Ionic liquids (ILs) are defined as salts that have melting points lower than 100°C. Most are organic salts, and these may be designed and tailored to have suitable properties. ILs are recognized as a third group of solvents (and electrolytes), after water and organic solvents. They are characterized by their unique properties such as nonvolatilities, high thermal stabilities, and high ionic conductivities. In this article, our work on the design and preparation of ILs is briefly reviewed. The concept of ionicity is proposed as a metric to characterize the basic nature (dissociativity) of ILs, which is affected by the Lewis acidity/basicity of cations/anions (i.e., coulombic interactions), the directionality of interactions between cations and anions, and van der Waals interactions between ions. The ionicity of ILs is dominated by a subtle balance between coulombic and van der Waals interactions, which clearly discriminates ILs from conventional high-temperature inorganic molten salts. Here, the design of protic ILs for fuel cell electrolytes, electron-transporting ILs for dye-sensitized solar cell electrolytes, and Li + -conducting solvate ILs for lithium battery electrolytes are discussed based on an understanding of the fundamental properties of ILs. Furthermore, the combination of ILs with polymers and colloidal particles affords intriguing quasi-solid materials (ion gels), and the ion transport in these gels is decoupled from the mechanical relaxation time of these materials, yielding new solid electrolytes. The possibility of temperature and photo-sensitive solubility dependence of polymers in ILs allows the creation of stimuli-responsive materials. Finally, protic ILs/protic salts are demonstrated to be good precursors for N-doped carbon materials.

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“…随着室温离子液体作为绿色溶剂而被广泛关注, 研究者们也将离子液体引入锂硫电池中, 其主要目的是利用离子液体的高黏度减少 2 S n -(4≤n≤8)向锂负极的扩散, 而锂离子在其中的传输不受影响, 最终提高锂硫电池的循环性能 [36,37] . Figure 3 Structural formula of PP14 and PP13…”

Section: Figureunclassified

“…2013 年, Watanabe 研究小组 [36] 合成了 N,N-二乙基- Figure 5 The contribution of the various components in DOL/LiTFSI＋ Li 2 S 6 ＋LiNO 3 solutions to the surface chemistry of Li electrodes [48] 除此之外, 还有其它不同类型的电解液添加剂被研究. …”

Section: Figureunclassified

Review of Electrolyte for Lithium Sulfur Battery

Jin¹,

Xie²,

Hong³

2014

Acta Chim. Sinica

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Of the high energy density chemical power systems currently being considered, lithium/sulfur (Li/S) batteries which use elemental sulfur as the cathode and lithium metal as the anode, are attracting increased attention in recent decades. Li/S batteries have a high energy density (2600 Wh/kg in theoretical, about 400 Wh/kg in practice nowadays), consist of abundant raw materials, are low cost and environmentally friendly. Although the rechargeable Li/S batteries possess more advantages over the conventional lithium ion batteries, the practical use faces with a variety of problems such as low utilization of sulfur and bad cycle life. Central to the operation of Li/S batteries are polysulfide anions ( 2 S n -, 4≤n≤8)], which are intermediate products generated during the electrochemical reduction process. These anions have high solubility in organic electrolytes. On the one hand, these anions typically diffuse to the lithium anode according to a concentration gradient and directly react with the anode. This diffusion causes an internal shuttle phenomenon and significantly corrodes the anode, which decreases active material utilization during the discharge process and reduces its cycle life. On the other hand, there are residual Li 2 S 2 and/or Li 2 S on the surface of sulfur cathode and Li anode even at 100% depth of charge. The formation of Li 2 S 2 and Li 2 S increasing with cycling results in active material loss. These drawbacks have seriously retarded industrial production of Li/S batteries. In this paper, combining with the works of our research team, the main research directions and the latest development of the electrolyte to enhance the cycle performance of Li-S batteries are reviewed from the aspects of the composition of the liquid electrolyte, the additives in liquid electrolyte, the polymer electrolyte and the inorganic electrolyte. At the meanwhile, the principle, the preparation of electrolyte, the influence on the performance of Li-S batteries, and problem in each research are analyzed. Finally, the further development of the electrolyte in Li-S battery is discussed.

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Solvent Effect of Room Temperature Ionic Liquids on Electrochemical Reactions in Lithium–Sulfur Batteries

Cited by 193 publications

References 84 publications

Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility

Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility

Design and Materialization of Ionic Liquids Based on an Understanding of Their Fundamental Properties

Review of Electrolyte for Lithium Sulfur Battery

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