The state of water in 1-butly-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide and its effect on Zn/Zn(II) redox behavior
The state of water in 1-butly-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide and its effect on Zn/Zn(II) redox behavior
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DOI：
10.1016/j.electacta.2013.03.027
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发表时间：
2013-05
影响因子：
6.6
通讯作者：
M. Xu;D. Ivey;Zhong Xie;W. Qu;E. Dy
中科院分区：
文献类型：
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作者：
M. Xu;D. Ivey;Zhong Xie;W. Qu;E. Dy
将水作为稀释剂添加到疏水性室温离子液体1-丁基-1-甲基吡咯烷双(三氟甲磺酰基)亚胺(BMP-TFSI)中，以提高其导电性，该离子液体被认为是锌空气电池潜在的电解液。研究了水在BMP-TFSI中的添加行为及其对BMP-TFSI中锌/锌(II)氧化还原行为的影响。通过DSC和FTIR分析以及密度泛函理论(DFT)模拟，确定了BMP-TFSI中存在两种类型的水，即自由水、非结合水和结合水。当水含量小于~2.0wt%时，水分子通过氢键与[TFSI]−阴离子相互作用。当水含量大于2.0wt%时，观察到水分子簇(游离水)。BMP-TFSI中的结合水降低了电化学反应的活化过电位，从而提高了锌/锌(II)氧化还原的可逆性。根据BMP-TFSI中锌/锌(II)氧化还原反应的动力学性质，最佳的加水量为2.0wt%。与未加水的BMP-TFSI相比，在水含量为2.0wt%的BMP-TFSI中，锌物种的扩散系数和锌/锌(II)氧化还原反应的交换电流密度都提高了约70%。
Water was added as a diluent into the hydrophobic room temperature ionic liquid (RTIL) 1-butly-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) with the purpose of improving the conductivity of the RTIL, which is being considered as a potential electrolyte for rechargeable Zn-air batteries. The behavior of water additions in BMP-TFSI and its effect on Zn/Zn(II) redox behavior in BMP-TFSI were studied. Two types of water, free or unbound water and bound water, were identified in BMP-TFSI through DSC and FTIR analysis and density functional theory (DFT) modeling. When the water content was less than ~2.0wt%, water molecules interacted with [TFSI]−anions through hydrogen bonding. When the water amount was greater than 2.0wt%, clusters of water molecules (free water) were observed. Bound water in BMP-TFSI improved Zn/Zn(II) redox reversibility by reducing the activation overpotential for electrochemical reactions. The optimal amount of water, in terms of the kinetic properties for Zn/Zn(II) redox in BMP-TFSI, was 2.0wt%. Compared with water-free BMP-TFSI, both the diffusion coefficient for the Zn species and the exchange current density for Zn/Zn(II) redox reactions increased by approximately 70% in BMP-TFSI with 2.0wt% water addition.