Although the utilization of deep eutectic solvents (DES) as non-aqueous electrolyte of redox flow batteries has received enormous attention, its properties like high viscosity and low conductivity always remain a matter of concern, due to their negative effect on final battery power performance. Herein, the introduction of two types of additive supporting electrolytes (one: a mixture of dimethyl carbonate (DMC) and ethylene carbonate (EC) and the other: ethyl acetate (EA)) remarkably decreasing the viscosity and impedance of the DES with iron ions is reported, especially for DMC+EC. In addition, the cyclic voltammetry results show that the reversibility of Fe(III)/Fe(II) redox couple, and the reaction kinetics are improved after adding DMC+EC, while EA has little effect on improving the electrochemical performance. From Raman spectroscopy, it is found that a distinct characteristic peak occurs at 895 cm⁻¹ for DMC+EC mixture, whereas the intensity of this peak is weak for EA. It is highly probable that the appearance of this characteristic peak serves to improve the electrochemical properties of DES.

Graphical abstract

尽管将深共熔溶剂（DES）用作氧化还原液流电池的非水电解质受到了广泛的关注，但由于其对最终电池功率性能的负面影响，其高粘度和低电导率之类的特性始终令人关注。在此，引入了两种类型的添加剂支持电解质（一种：碳酸二甲酯（DMC）和碳酸亚乙酯（EC）的混合物，另一种：乙酸乙酯（EA））显着降低了DES与铁离子的粘度和阻抗据报道，特别是对于DMC + EC。此外，循环伏安法结果表明，添加DMC + EC后，Fe（III）/ Fe（II）氧化还原对具有可逆性，反应动力学得到改善，而EA对改善电化学性能影响不大。根据拉曼光谱，对于DMC + EC混合物，为^-1，而对于EA，此峰的强度较弱。该特征峰的出现很有可能用于改善DES的电化学性能。

图形概要