Chaotic Phenomenon in Vanadium Redox Flow Battery

Abstract

the vanadium compounds during the charging process. Studies were most focused on the materials of electrodes, [13][14][15] and modification of membrane. [16][17][18][19] Few studies had reported the electrochemical behavior of anolyte during the charging process.All chemicals were analytical grade. Water was purified with a water purification system (HMC-WS 10, Korea). The anolyte was composed of VOSO 4 (1 M) and H 2 SO 4 (2 M), and the catholyte was H 2 SO 4 (2 M) with the same volume. The anolyte and catholyte was separated with a Nafion membrane. The anode and cathode used in the experiments was platinum slice (1.5x2 cm) in which no other unexpected side reaction occurred. They were subjected to ultrasonic cleaning in de-ionized water for 30 min to remove residues before testing. Electrochemical tests were carried out on CHI660D electrochemical workstation. The signal of the potential was amplified, and the times series were recorded and transferred to a personal computer. The macro-instability frequency, oscillation period, of the potential-time series were obtained using Matlab.Electrochemical oscillation was observed during the charging process, while the electrochemical tests were carried out on CHI660D electrochemical workstation with the anolyte of 1 M VOSO 4 +2 M H 2 SO 4 , and the catholyte of 2 M H 2 SO 4 at room temperature, the potential-time series was showed in Figure 1. As indicated in Figure 1 the potential was increased quickly and then electrochemical oscillation emerged. After then, the period of the electrochemical oscillation slowly decreased and then stabilized as showed in Figure 2.The power consumption was investigated to reveal the influence of electrochemical oscillation on the charging efficiency. An extra power consume was a result of the electrochemical oscillation.The relative power-consume (PRC) was calculated as PRC= the average power consumption on anode / (Va·Ia), where Va was the potential, Ia was the charging potential. The results were shown in Figure 3. The influence of electrochemical oscillation on the charging efficiency will be enlarge in long-term charging, and much extra power will be consumed. This part of power consumption should exist in practical charging process, even though it is often ignored. It is beneficial for improving the charge efficiency and energy-saving if the electrochemical oscillation could be regulated. The mechanism of the electrochemical oscillation was investigated. During the charging process, the main chemical reactions in the system were described in Equation (1) Short communicationVanadium redox flow battery is an efficient energy-storage system because it's long cycle life, flexible design, high efficiency and fast response time. Chaotic phenomenon (electrochemical oscillation) was first observed during the charging process of the anolyte, and the mechanism was investigated. The largest Lyapunov exponent was applied to characterize the chaotic phenomenon.Vanadium and its compounds are used for manufacturing iron [1][2][3] steel non-fer...

Electrochemical oscillation of vanadium ions in anolyte

“…The experimental process was nearly the same as presented before [10]. The anolyte was composed of VOSO4 (varied from 0.5 M to 1.5 M) and H2SO4 (2 M), and the catholyte was H2SO4 (2 M) with the same volume.…”

“…The all-vanadium redox flow batteries (VRFBs) proposed by Skyllas-Kazacos et al as an efficient energy-storage systems [6] have attracted attention for their long life time, flexible design, high efficiency and fast response time [7]. The main components of VRFB are electrolytes, membranes [8][9][10] and electrodes [11][12][13]. The reaction that occurs at the positive electrode of the VRFB during charge and discharge process is defined as follows:…”

Separation and Recovery of Vanadium and Chromium from Liquor Solution by Fractional Precipitation

“…Vanadium and chromium are important metalsused for manufacturing iron, steel non-ferrous metals, andpetrochemicals because of their excellent physicochemical properties [1][2][3]. Many hydrometallurgical processes had been applied to leach out vanadium and chromium, including sub-molten salt technology [4,5], alkaline electrochemical advanced oxidation process [6][7][8][9], roasting-leaching technology [10][11][12], pressure leaching [13], .etc.…”