| There has been an urgent requirement for exploiting the renewable energy to deal with the energy crisis and environmental issue. Renewable energy such as wind, solar, possesses the feature of environment friendly and exhaust-less. However, it has the inherent faults of intermittent and volatility. Therefore, its broad application must have the advanced large-scale energy storage system as support. All vanadium redox flow battery (VRB) with the advantages of low-cost, high efficiency and deep discharge ability, earns a bright application prospect for large-scale energy storage. This paper introduced the structure and working principle of VRB, reviewed the research progress of critical materials for VRB, and studied several electrode materials for positive or negative side and the performance of 5 kW class VRB stack with mutil-channel flow frame.1?Functional porous carbon (PC) derived from shaddock peel has been explored as catalyst for vanadium redox flow battery (VRB). The prepared PC is micro-mesoporous with high BET surface area of 882.7 m2/g, and has some surface oxygen-containing functional groups and P-doped defect sites. The electrochemical activity of VO2+/VO2+on the PC modified glass carbon (PC-GC) is greatly enhanced. Compared with the GC and graphite modified GC (G-GC), the PC-GC presents a lower peak voltage separation (66 mV), higher anodic current density (17.1 mA/cm2) and cathodic current density (15.0 mA/cm2). The VRB (PC-GF-B) using PC modified graphite felt (GF) as positive electrode demonstrates an enhanced electrochemical performance. It presents a higher average voltage efficiency and energy efficiency of 82.7% and 80.1% at the current density of 60 mA/cm2, enhanced by about 3.8% and 3.4% as compared with viriginal VRB (GF-B), respectively.2?Micrometer Sb particles are well deposited on the surface of graphite felt (GF) as catalysts for the redox reaction of V3+/V2+by pulse electro-deposition. The physical properties of Sb-GF are characterized by Field emission scanning electron microscopy (FE-SEM), Energy diffraction spectroscopy (EDS) and X-ray diffraction (XRD). Cyclic voltammetry (CV). Electrochemical impedance spectroscopy (EIS) and Charge/discharge test verify that Sb particles are of excellent electrochemical catalytic activity for the negative reaction. The voltage efficiency and energy efficiency of VRB (Sb-GF-B) with Sb-GF as negative electrode are 87.6% and 84.6% at the current density of 60 mA/cm2, respectively. These values are much better than those of virginal VRB (GF-B). It also demonstrates an excellent rate performance. The voltage efficiency of Sb-GF-B remains 79%, even at the current density increasing up to 100 mA/cm2, much better than that of GF-B.3?A flow frame with multi-distribution channels is designed and the electrolyte distribution in the electrode is simulated by a commercial computational fluid dynamics (CFD) package of Star-CCM+. The result shows that the flow frame possesses excellent flow distribution ability. Then, a 5 kW class vanadium redox flow battery (VRB) stack is successfully assembled with that flow frame, and its electrochemical performance is investigated. The stack presents an excellent performance. When charging/discharging at the current density of 60 mA cm"2, it delivers a current efficiency and energy efficiency of 93.9% and 80.8%, respectively, with an average output power of 5.5 kW. The higher average output power of 7.2 kW is obtained at the current density of 80 mA cm-2 with energy efficiency of 78.4%. It also presents an excellent cycling performance as well as even voltage distribution, the standard deviation of voltage at the current density of 80 mA cm-2 under the SOC value of 20%,80% and SOD value of 80% are 16.48,16.46 and 23.62 mV, respectively. The results from the kW class stack are of great value to promote the application of VRBs. |
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