The impact of solvent properties on the performance of oxygen reduction and evolution in mixed tetraglyme-dimethyl sulfoxide electrolytes for Li-O2 batteries: Mechanism and stability
The impact of solvent properties on the performance of oxygen reduction and evolution in mixed tetraglyme-dimethyl sulfoxide electrolytes for Li-O2 batteries: Mechanism and stability
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DOI：
10.1016/j.electacta.2017.06.012
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发表时间：
2017-08-10
影响因子：
6.6
通讯作者：
Baltruschat, Helmut
中科院分区：
文献类型：
--
作者：
Amin, Hatem M. A.;Molls, Christoph.;Baltruschat, Helmut
电解液的不稳定性和反应动力学缓慢阻碍了锂离子电池的应用。本研究利用旋转环盘电极（RRDE）和差分电化学质谱（DEMS）技术，深入研究了二甲亚砜（DMSO）、四烯胺（G4）及其共混物DMSO-G4中氧还原（ORR）和进化（OER）反应的行为，重点研究了溶剂性质在反应机理和反应途径中的作用。有趣的是，RRDE结果表明，形成的O-2（-）的稳定性和比例。： G4中DMSO的加入使Li2O2增加。讨论了一种拟议的ORR机制。根据溶剂的溶剂化能力，这主要决定了超氧化物中间体在溶液中的寿命和溶解度，遵循溶液或表面途径：在高溶剂化溶剂中（例如具有高供体或受体数的溶剂），如DMSO，超氧化物在溶液中稳定；而在低溶剂化溶剂中，它进一步还原为Li2O2，阻塞表面。在DMSO中定义的质量传递下，扫描速率变化的结果表明，在还原过程中，Li2O2单层的顺序形成。在g4溶液中，尽管Li2O2的形成是可逆的，但电极的失活发生了，这是由dem证明的。这可能是由于还原产物引起的电解液分解，在ORR过程中在表面形成失活膜，在高电位释放二氧化碳时仅部分去除。此外，我们发现DMSO比G4对OER更活跃。电极材料也影响动力学，特别是OER。这些发现可能会对锂空气电池的发展产生影响。(C) 2017 Elsevier Ltd.版权所有。
The instability of the electrolyte and the sluggish kinetics of the reactions hinder the application of Li-O-2 batteries. In this study, we aim to better understand the behavior of oxygen reduction (ORR) and evolution (OER) reactions in dimethyl sulfoxide (DMSO), Tetraglyme (G4) and their blend DMSO-G4, with emphasis on the role of solvent nature in the mechanism and reaction route, using rotating ring-disc electrode (RRDE) and differential electrochemical mass spectrometry (DEMS). Interestingly, RRDE results showed that the stability and the ratio of the formed O-2(-.) : Li2O2 increase with addition of DMSO to G4. A proposed mechanism for ORR is discussed. Depending on the solvation ability of the solvent, which primarily determines the lifetime and solubility of the superoxide intermediate in solution, a solution or a surface-based pathway is followed: in highly solvating solvents (e.g. those with high donor or acceptor number) such as DMSO, superoxide is stabilized in solution; while in low solvating solvent, it is further reduced to Li2O2, blocking the surface. The results of the scan rate variation under defined mass transport in DMSO suggest a sequential formation of monolayers of Li2O2 during reduction. In G4-solutions, despite of the reversible formation of Li2O2, deactivation of the electrode takes place, as evidenced by DEMS. This could arise from a reduction products-induced decomposition of the electrolyte, forming a deactivating film on the surface during ORR, which is only partially removed at higher potentials evolving CO2. Also, we found that DMSO is more active towards OER than G4. The electrode material as well influences the kinetics, in particular of OER. These findings could have implications for the development of Li-air battery. (C) 2017 Elsevier Ltd. All rights reserved.