| Summary: | 碩士 === 輔仁大學 === 化學系 === 107 === In this study, the diammonium phosphate ((NH4)2HPO4) and ammonium dihydrogen phosphate (NH4H2PO4) are investigated as additives to improve the stability of a vanadium electrolyte(1.67 M Vn+ / 3 M H2SO4) for a vanadium redox flow battery (VRFB) at operating temperatures of 5℃ and 45℃. The most effective additive is chosen based on the thermal stability and electrochemical performance with a long inhibition time. Through precipitation time and electrochemical measurements, the results show that the best inhibition effect is achieved by adding 0.1M NH4H2PO4 as an additive, indicating an improved redox reversibility and electrochemical activity. At the temperature of 45 ° C and a current density of 60 mA / cm2, the charge/discharge energy efficiency of the electrolyte with 0.10 M NH4H2PO4 is 86 %, same as the origin electrolyte. In the cycle-life test, the cycling number is increased from 40 cycles to 205 cycles after adding 0.10 M NH4H2PO4. At a low temperature of 5 °C and a current density of 60 mA/cm2, the charge/discharge energy efficiency of electrolyte without and with 0.10 M NH4H2PO4 are 84.7 % and 83.5 %, respectively. In the cycle-life test, the cycling number is increased from 46 cycles to 147 cycles after adding 0.10 M NH4H2PO4.
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