Reynard Danick, Maye Sunny, Peljo Pekka, Chanda Vimanshu, Girault Hubert H, Gentil Solène
Laboratoire d'Électrochimie Physique et Analytique, École Polytechnique Fédérale de Lausanne, EPFL, Valais Wallis, Rue de l'industrie, 17, 1950, SION, Switzerland.
Research group of Physical Electrochemistry and Electrochemical Physics, Department of Chemistry and Materials Science, Aalto University, Keminstintie 1, PO BOX 16100, 00076, Aalto, Finland.
Chemistry. 2020 Jun 5;26(32):7250-7257. doi: 10.1002/chem.202000340. Epub 2020 May 19.
The Mn /Mn redox couple with a standard potential of +1.51 V versus the standard hydrogen electrode (SHE) has attracted interest for the design of V/Mn redox flow batteries (RFBs). However, Mn disproportionation leads to a loss of capacity, an increase in pressure drop, and electrode passivation caused by the formation of MnO particles during battery cycling. In this work, the influence of Ti or/and V on Mn stability in acidic conditions is studied by formulating four different electrolytes in equimolar ratios (Mn, Mn/Ti, Mn/V, Mn/V/Ti). Voltammetry studies have revealed an EC process for Mn oxidation responsible for the electrode passivation. SEM and XPS analysis demonstrate that the nature and morphology of the passivating oxides layer depend strongly on the electrolyte composition. Spectroelectrochemistry highlights the stabilization effect of Ti and V on Mn . At a comparable pH, the amount of Mn loss through disproportionation is decreased by a factor of 2.5 in the presence of Ti or/and V . Therefore, V is an efficient substitute for Ti to stabilize the Mn electrolyte for RFB applications.
相对于标准氢电极（SHE），标准电位为+1.51 V的Mn/Mn氧化还原电对已引起人们对钒/锰氧化还原液流电池（RFB）设计的兴趣。然而，在电池循环过程中，锰的歧化反应会导致容量损失、压降增加以及由MnO颗粒形成引起的电极钝化。在这项工作中，通过配制四种等摩尔比的不同电解质（Mn、Mn/Ti、Mn/V、Mn/V/Ti），研究了Ti或/和V在酸性条件下对Mn稳定性的影响。伏安法研究揭示了导致电极钝化的Mn氧化的EC过程。扫描电子显微镜（SEM）和X射线光电子能谱（XPS）分析表明，钝化氧化层的性质和形态强烈依赖于电解质组成。光谱电化学突出了Ti和V对Mn的稳定作用。在可比的pH值下，在存在Ti或/和V的情况下，通过歧化反应损失的Mn量减少了2.5倍。因此，V是Ti的有效替代品，可稳定用于RFB应用的Mn电解质。
