Abstract:

Compared with conventional aqueous electrolyte, deep eutectic solvent(DES) has been studied as the electrolyte of flow battery for its unique advantages. However, its physical and electrochemical properties are more sensitive to the temperature and related researches can hardly be found in open literature. The aim of the work is to study the physical and electrochemical properties of vanadium ions in DES through varying the operating temperatures. The curves of cyclic voltammetry indicate that vanadium ions show a quasi-reversible reaction. As the temperature increased from ambient temperature to 55℃, the difference between oxidation and reduction peaks decreases from 0.271 V to 0.249 V at the scan rate of 100 mV·s^-1. At the same time, both the anodic and the cathodic peak current densities of the V(Ⅱ)/V(Ⅲ) have the similarly incremental trend. The conductivity also has an obvious increment from 2.2 mS·cm^-1 at ambient temperature to 11.16 mS·cm^-1 at 55℃, but the viscosity of DES vanadium ions have a huge drop. The results prove that the operating temperature plays a vital effect on the characteristics of DES and it deserves a further study.

Key words: deep eutectic solvent, vanadium ion, electrochemistry, temperature effect, electrolytes

摘要：

相比于传统水系电解质，低共熔溶剂（DES）因其所具有的独特优势，越来越多地被作为液流电池的电解液进行研究。DES的物理属性和电化学特性对温度较为敏感，但迄今为止对其研究较少。报道了温度对VCl₃在DES中的物理化学特性的影响。在100 mV·s^-1的扫速时，循环伏安（CV）曲线说明在25℃时，钒离子呈现准可逆的状态；随着温度从室温升高至55℃，氧化峰与还原峰之差从0.271 V降低至0.249 V。随着温度的增加，电导率也明显增加，从室温时的2.2 mS·cm^-1升高至55℃时的11.16 mS·cm^-1，而且黏度出现较大的下降。结果表明温度对DES特性的影响巨大，有必要更加深入研究温度对非水系电解液液流电池性能的影响。

关键词: 低共熔溶剂, 钒离子, 电化学, 温度效应, 电解质