A protic ionic liquid is designed and implemented for the first time as a solvent for a high energy density vanadium redox flow battery. Despite being less conductive than standard aqueous electrolytes, it is thermally stable on a 100 °C temperature window, chemically stable for at least 60 days, equally viscous and dense with typical aqueous solvents and most importantly able to solubilize to 6 mol L^-1 vanadium sulfate, thus increasing the VRFB energy density by a factor of 2.5. Electrochemical measurements revealed quasi-reversible redox transitions for both catholyte and anolyte at 25 °C while a proof-of-concept redox flow cell with the proposed electrolyte was tested for a total of 150 cycles at 25 °C, showing an open circuit potential of 1.39 V and energy and coulombic efficiencies of 65% and 93%, respectively. What’s more, the battery can be equally cycled at 45 °C showing good thermal stability. This study underlines a new route to improve the energy-to-volume ratio of this promising energy storage system.

质子性离子液体首次设计和实现为高能量密度钒氧化还原液流电池的溶剂。尽管其导电性不如标准的水性电解质，但它在100°C的温度范围内具有热稳定性，化学稳定性至少60天，与典型的水性溶剂一样粘稠且稠密，最重要的是能够溶解至6 mol L ^-1硫酸钒，因此将VRFB能量密度提高了2.5倍。电化学测量显示，在25°C时，阴极电解液和阳极电解液均发生准可逆的氧化还原转变，而在25°C下测试了带有拟议电解质的概念验证氧化还原流通池共进行150次循环，表明开路电位为1.39 V和能量和库仑效率分别为65％和93％。此外，电池可以在45°C下均匀循环，显示出良好的热稳定性。这项研究强调了改善这种有前途的储能系统的能量体积比的新途径。