Study Of Positive Electrolyte For Zinc-cerium Redox Flow Battery Application

Investigation of Ce3+/Ce4+electrolyte for zinc-cerium redox flow battery application has been intensively carried out. This paper is divided into six parts:Redox flow cell technology is a new electrical energy storage technology with advantages of large scale and high efficiency. It can meet the great demands of boosting the wide application of the renewable resources, facilitating the construction of smart grid and accomplishing the target for energy saving and emission reduction. In this charpter, we centre around the introduction to the working principles, characteristics, research status at home and abroad of the all-vanadium, all-chromium, sodium polysulfide-bromine, zinc-bromine, soluble lead and zinc-cerium redox flow battery et al.. Chemical properties of some redox couples have been introduced detailedly.Electrode process and electrolyte stability of Ce3+/Ce4+in methane sulfonic acid (MSA) media were investigated. The standard rate constant of the Ce3+/Ce4+electrode reaction on graphite is4.06×10-4cm s-1. The diffusion coefficient of Ce3+in MSA is5.18～5.56×10-6cm2s-1,it is2.56～2.68×10-6cm2s-1for Ce4+. The rate of electrolyte precipitation is dependent on temperature, cerium and MSA concentrations as well as the state of charge of the electrolyte. The energy efficiency of zinc-cerium redox flow cell is74.8%at20mA cm-2current.Electrode process and electrolyte stability of Ce3+/Ce4+in mixed acid media were investigated. The standard rate constant of the Ce3+/Ce4+electrode reaction in mixed acid media is4.17×10-4cm s-1. The diffusion coefficients of Ce3+/Ce4+in mixed acid are larger than that in single acid. The solubility of cerium salt in mixed acid is larger than that in sulfuric acid; a solution of1mol dm-3Ce3+/Ce4++2mol dm-3CH3SO3H+0.5mol dm-3H2SO4is sufficiently stable for30days at temperatures up to313K. Energy efficiency of the test cell using mixed acid electrolyte is higher than that using single CH3SO3H electrolyte.The effect of additives (sulfosalicylic acid, DTPA, Cobaltous acetate et al.) on kinetics of Ce3+/Ce4+electrode reaction and solubility of Ce3+/Ce4+electrolyte was investigated. Some additives (Sulfosalicylic acid and DTPA et al.) can improve kinetics of Ce3+/Ce4+electrode reaction and solubility of Ce3+/Ce4+electrolyte; Cobaltous acetate only has positive effect on kinetics of Ce3+/Ce4+electrode reaction without improvement of electrolyte stability.Study of mixed electrolyte used in redox flow cell to improve volume special energy was carried out. The results show that, charge-discharge capacity of zinc-cerium&nitroso as well as zinc-cerium&ferrum redox flow cell is larger than that of zinc-cerium redox flow cell. Performance of zinc-cerium&ferrum redox flow cell is better than that of zinc-cerium&nitroso redox flow cell at large charge-discharge current.Some important conclusions, market prospect, development bottleneck and development direction about redox flow battery were summarized in this charpter. It is pointed out that development of zinc-cerium redox flow battery technology is important area and direction for change step by step from country with rich rare earths sources to strong country with technology.