Ionic liquid of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide(PP13TFSI)-based electrolytes for lithium–sulfur batteries
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- 英文论文题名：Ionic liquid of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide(PP13TFSI)-based electrolytes for lithium–sulfur batteries
- 论文作者：王丽娜 ; Minglin Sun ; Yonggang Wang ; Tianxi Liu ; Yongyao Xi
- 英文论文作者：Lina Wang ; Minglin Sun ; Yonggang Wang ; Tianxi Liu ; Yongyao Xi ; State Key Laboratory of Modification of Chemical Fibers and Polymer Materials ; College of Materials Science and Engineering ; Donghua University ; Department of Chemistry ; Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials ; Institute of New Energy ; and Collaborative Innovation Center of Chemistry for Energy Materials ; Fudan University
- 年：2016
- 作者机构：State Key Laboratory of Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University;Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Institute of New Energy, and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University;
- 会议召开时间：2016-10-28
- 会议录名称：2016淮海绿色功能材料论坛暨第三届徐州清洁能源材料论坛摘要集
- 语种：英文
- 分类号：TM912
- 学会代码：ZGHY
- 会议名称：2016淮海绿色功能材料论坛暨第三届徐州清洁能源材料论坛
- 会议地点：中国江苏徐州
- 主办单位：中国化学会
- 学会名称：中国化学会
- 页数：3
- 文件大小：714k
- 原文格式：D
- 会议级别：全国
摘要
The Lithium-sulfur(Li–S) batteries are receiving tremendous attention due to their potential for high energy-density batteries in emerging electronics and vehicle applications. However, severe self-discharge associated with a rapid polysulfide redox shuttle process has remained a grand challenge, preventing the practical application of this attractive technology. Soluble polysulfide species(Li_2S_x, 4 ≤ x ≤ 8) would continue to dissolve and migrate to negative side because of concentration gradient, and then react with metallic Li, resulting in decrease of open-circuit voltage, loss of upper discharge plateau and discharge capacity. The dissolution and diffusion of polysulfides is determined largely by the physicochemical properties of organic electrolytes. Owing to the strongly nucleophilic reactivity of polysulfide anions, the electrolyte solvents of Li–S cells are mainly limited within the cyclic and linear ethers, such as 1,3-dioxolane(DOL) and 1,2-dimethoxyethane(DME).1,2 However, this type of electrolyte readily solubilizes the Li_2S_x species(especially, x ≥ 4) and actually functions as a catholyte after the first discharge in Li-S cells.3 To address this issue, we take a different approach to Li–S batteries by developing a room temperature ionic liquid(RTIL) of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide(PP13TFSI)-based electrolytes. When working together with LiNO_3, zero self-discharge can be achieved to rest a full-charged cell for two days. To confirm the effect of PP13 TFSI on the cell performance, solubility test was conducted by synthesizing 0.5 M of Li_2S_x in DOL/DME or PP13TFSI/DOL/DME mixture solvent according to the method reported by Rauh et al.4 The images after 24 h of standing are shown in Fig. 1a. Most of Li_2S_8 is dissolved in DOL/DME solvent with negligible precipitation, giving rise to a dark-brown solution. Less dissolution is expected in the solvent of PP13TFSI/DOL/DME by the more precipitation observed at the vial bottom. It is concluded that the high solubility of Li_2S_x in DOL/DME result in a rapid diffusion of polysulfide species into the electrolyte. Instead, the large ratio of PP13 TFSI leads to less polysulfide dissolution and slower diffusion speed of polysulfides. The function mechanism is proposed in the schematic illustration of Fig. 1b. The low solubility of Li_2S_x in the PP13TFSI-based solution can be explained in terms of the donor ability of solvents, because dissolution of ionic Li_2S_x is thought to be principally dominated by the solvation of Li+ ions of Li_2S_x with solvent molecular/anions.3,5 Indeed, TFSI-anions are able to solvate the Li+ of Li_2S_x through O atoms of two sulfony groups.6 Nevertheless, the typical RTIL of PP13 TFSI consist of weakly Lewis acidic cation and weakly Lewis basic anion. The weakly Lewis basic nature of TFSI-anion induces decreased coordination ability with Li~+. Instead, the ether solvents have high donor number would preferentially coordinate with Lewis acidic cations of Li+. For this reason, DME and DOL can readily solubilize Li_2S_x. 100% CE also can be achieved for the cells with electrolytes containing LiNO_3 additive, implying the prohibited polysulfide shuttle.
The Lithium-sulfur(Li–S) batteries are receiving tremendous attention due to their potential for high energy-density batteries in emerging electronics and vehicle applications. However, severe self-discharge associated with a rapid polysulfide redox shuttle process has remained a grand challenge, preventing the practical application of this attractive technology. Soluble polysulfide species(Li_2S_x, 4 ≤ x ≤ 8) would continue to dissolve and migrate to negative side because of concentration gradient, and then react with metallic Li, resulting in decrease of open-circuit voltage, loss of upper discharge plateau and discharge capacity. The dissolution and diffusion of polysulfides is determined largely by the physicochemical properties of organic electrolytes. Owing to the strongly nucleophilic reactivity of polysulfide anions, the electrolyte solvents of Li–S cells are mainly limited within the cyclic and linear ethers, such as 1,3-dioxolane(DOL) and 1,2-dimethoxyethane(DME).1,2 However, this type of electrolyte readily solubilizes the Li_2S_x species(especially, x ≥ 4) and actually functions as a catholyte after the first discharge in Li-S cells.3 To address this issue, we take a different approach to Li–S batteries by developing a room temperature ionic liquid(RTIL) of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide(PP13TFSI)-based electrolytes. When working together with LiNO_3, zero self-discharge can be achieved to rest a full-charged cell for two days. To confirm the effect of PP13 TFSI on the cell performance, solubility test was conducted by synthesizing 0.5 M of Li_2S_x in DOL/DME or PP13TFSI/DOL/DME mixture solvent according to the method reported by Rauh et al.4 The images after 24 h of standing are shown in Fig. 1a. Most of Li_2S_8 is dissolved in DOL/DME solvent with negligible precipitation, giving rise to a dark-brown solution. Less dissolution is expected in the solvent of PP13TFSI/DOL/DME by the more precipitation observed at the vial bottom. It is concluded that the high solubility of Li_2S_x in DOL/DME result in a rapid diffusion of polysulfide species into the electrolyte. Instead, the large ratio of PP13 TFSI leads to less polysulfide dissolution and slower diffusion speed of polysulfides. The function mechanism is proposed in the schematic illustration of Fig. 1b. The low solubility of Li_2S_x in the PP13TFSI-based solution can be explained in terms of the donor ability of solvents, because dissolution of ionic Li_2S_x is thought to be principally dominated by the solvation of Li+ ions of Li_2S_x with solvent molecular/anions.3,5 Indeed, TFSI-anions are able to solvate the Li+ of Li_2S_x through O atoms of two sulfony groups.6 Nevertheless, the typical RTIL of PP13 TFSI consist of weakly Lewis acidic cation and weakly Lewis basic anion. The weakly Lewis basic nature of TFSI-anion induces decreased coordination ability with Li~+. Instead, the ether solvents have high donor number would preferentially coordinate with Lewis acidic cations of Li+. For this reason, DME and DOL can readily solubilize Li_2S_x. 100% CE also can be achieved for the cells with electrolytes containing LiNO_3 additive, implying the prohibited polysulfide shuttle.
The Lithium-sulfur(Li–S) batteries are receiving tremendous attention due to their potential for high energy-density batteries in emerging electronics and vehicle applications. However, severe self-discharge associated with a rapid polysulfide redox shuttle process has remained a grand challenge, preventing the practical application of this attractive technology. Soluble polysulfide species(Li_2S_x, 4 ≤ x ≤ 8) would continue to dissolve and migrate to negative side because of concentration gradient, and then react with metallic Li, resulting in decrease of open-circuit voltage, loss of upper discharge plateau and discharge capacity. The dissolution and diffusion of polysulfides is determined largely by the physicochemical properties of organic electrolytes. Owing to the strongly nucleophilic reactivity of polysulfide anions, the electrolyte solvents of Li–S cells are mainly limited within the cyclic and linear ethers, such as 1,3-dioxolane(DOL) and 1,2-dimethoxyethane(DME).1,2 However, this type of electrolyte readily solubilizes the Li_2S_x species(especially, x ≥ 4) and actually functions as a catholyte after the first discharge in Li-S cells.3 To address this issue, we take a different approach to Li–S batteries by developing a room temperature ionic liquid(RTIL) of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide(PP13TFSI)-based electrolytes. When working together with LiNO_3, zero self-discharge can be achieved to rest a full-charged cell for two days. To confirm the effect of PP13 TFSI on the cell performance, solubility test was conducted by synthesizing 0.5 M of Li_2S_x in DOL/DME or PP13TFSI/DOL/DME mixture solvent according to the method reported by Rauh et al.4 The images after 24 h of standing are shown in Fig. 1a. Most of Li_2S_8 is dissolved in DOL/DME solvent with negligible precipitation, giving rise to a dark-brown solution. Less dissolution is expected in the solvent of PP13TFSI/DOL/DME by the more precipitation observed at the vial bottom. It is concluded that the high solubility of Li_2S_x in DOL/DME result in a rapid diffusion of polysulfide species into the electrolyte. Instead, the large ratio of PP13 TFSI leads to less polysulfide dissolution and slower diffusion speed of polysulfides. The function mechanism is proposed in the schematic illustration of Fig. 1b. The low solubility of Li_2S_x in the PP13TFSI-based solution can be explained in terms of the donor ability of solvents, because dissolution of ionic Li_2S_x is thought to be principally dominated by the solvation of Li+ ions of Li_2S_x with solvent molecular/anions.3,5 Indeed, TFSI-anions are able to solvate the Li+ of Li_2S_x through O atoms of two sulfony groups.6 Nevertheless, the typical RTIL of PP13 TFSI consist of weakly Lewis acidic cation and weakly Lewis basic anion. The weakly Lewis basic nature of TFSI-anion induces decreased coordination ability with Li~+. Instead, the ether solvents have high donor number would preferentially coordinate with Lewis acidic cations of Li+. For this reason, DME and DOL can readily solubilize Li_2S_x. 100% CE also can be achieved for the cells with electrolytes containing LiNO_3 additive, implying the prohibited polysulfide shuttle.
引文
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