摘要
Redox flow batteries are considered a promising technology for grid energy storage.However,capacity decay caused by crossover of active materials is a universal challenge for many flow battery systems,which are based on various chemistries.In this paper,using the vanadium redox flow battery as an example,we demonstrate a new gel polymer interface(GPI)consisting of crosslinked polyethyleneimine with a large amount of amino and carboxylic acid groups introduced between the positive electrode and the membrane.The GPI functions as a key component to prevent vanadium ions from crossing the membrane,thus supporting stable long-term cycling.Cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)measurements were conducted to investigate the effect of GPI on the electrochemical properties of graphitic carbon electrodes(GCFs)and redox reaction of catholyte.X-ray photoelectron spectroscopy(XPS)and ^(1)H nuclear magnetic resonance(NMR)spectra demonstrated that the crosslinked GPI is chemically stable for 100 cycles without dissolution of polymers and swelling in the strong acidic electrolytes.Results from inductively coupled plasma mass spectrometry(ICP-MS),Fourier-transform infrared(FTIR)spectroscopy,and energy-dispersive X-ray(EDX)spectroscopy proved that the GPI is effective in maintaining the concentration of vanadium species in their respective half-cells,resulting in improved cycling stability because of it prevents active species from crossing the membrane and stabilizes the oxidation states of active species.
基金
The authors would like to acknowledge financial support primarily from the U.S.Department of Energy’s Office of Electricity OE(under Contract No.70247)
The XPS and NMR and UV-vis measurements were performed at the Environmental Molecular Sciences Laboratory EMSL,a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory(PNNL).PNNL is a multiprogram national laboratory operated by Battelle for DOE under Contract DE-AC05-76RL01830.
