The electrolyte is one of the most important components of the vanadium redox flow battery and its properties will affect cell performance and behavior in addition to the overall battery cost. Vanadium exists in several oxidation states with significantly different half-cell potentials that can produce practical cell voltages. It is thus possible to use the same element in both half-cells and thereby eliminate problems of cross-contamination inherent in all other flow battery chemistries. Electrolyte properties vary with supporting electrolyte composition, state-of-charge, and temperature and this will impact on the characteristics, behavior, and performance of the vanadium battery in practical applications. This Review provides a broad overview of the physical properties and characteristics of the vanadium battery electrolyte under different conditions, together with a description of some of the processing methods that have been developed to produce vanadium electrolytes for vanadium redox flow battery applications.
This paper provides a systematic approach to investigate the reaction of V(IV)/V(V) redox couple and mainly focuses on the effect of surface roughness and functional groups derived from the pre-treatment on the electrochemical behavior of glassy carbon in V(IV)/V(V) solutions. 600-grit, 1200-grit and 4000-grit SiC sandpapers were utilized to change the roughness of the electrode surfaces. Cyclic voltammetry (CV) within different potential ranges were applied in advance to alter oxygen functional groups on the electrode surface as well as surface roughness. CV and electrochemical impedance spectroscopy (EIS) were then used to investigate the electrode behavior in 1 M V(IV)/V(V) (1:1) solution on glassy carbon electrodes. Scanning electron microscopy (SEM) was employed to characterize the surface roughness. X-ray photoelectron spectroscopy (XPS) was adopted to analyze the surface oxygen functional groups. It is shown that polishing and CV scans within different potential ranges can vary the electrochemical response of glassy carbon to V(IV)/V(V) couples significantly. Increased surface roughness is seen to be beneficial for the redox reaction while oxygen functional groups such as C=O and C-O-C tends to reduce the activity of glassy carbon.
A multilayer structured cathode for zinc ion batteries is created by using vertical graphene nano-maze to hold MnO2 and encapsulating with an ionic conductive PEDOT:PSS layer. The new electrode exhibits exceptional capacity and cycle performance.
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