Research On Electrolyte And Electrode Materials Of Zn/Fe Flow Battery

Widespread use of renewable energy sources such as solar and wind to replace fossil fuels is one of the best strategies to avoid catastrophic consequences of the greenhouse effect.But the intermittent nature of solar and wind energy poses a huge challenge to the safety of the grid.The development of smart grid requires a reliable energy storage device to adjust the power input and output to achieve the highest energy utilization efficiency.The redox flow battery has become one of the most promising large-scale energy storage devices due to its fast response,rapid charge and discharge and high safety performance.In this paper,the properties of positive and negative electrolyte and electrode material of Zn/Fe liquid flow battery were studied.The structures and properties of various electrode materials were characterized.The results are as follows:Fe²⁺/Fe³⁺electric pair is combined with different ligands,and its form potential is different,which decreases with the increase of acid concentration in sulfuric acid medium.The oxidation process and reduction process of Fe²⁺/Fe³⁺electric pair in ammonium sulfate solution are calculated by calculation.The diffusion coefficients are 7.02×10^-66 cm²/s,1.81×10^-5 cm²/s,respectively,and the iron ion pair is a quasi-reversible system;the ferrous ion is easily oxidized at normal temperature,and hydrolysis occurs to form a precipitate.The stability of the solution can be improved by adjusting the pH.When the solubility of iron ions is 0.1 mol/L and the acid concentration is 2.0 mol/L,the solution is the most stable;1.5 mol/L ZnSO₄ solution is used as the negative electrode electrolyte,the 1.5 mol/L FeCl₂ and 2 mol/L H₂SO₄ solution was used as the positive electrode electrolyte for the static charge and discharge experiments.The coulombic efficiency of Zn/Fe RFB reached 83.6%,the energy efficiency was 56%,and the discharge medium pressure was 1.12 V.The diffusion rates of Zn/Zn²⁺pairs in weak acid medium,neutral strong electrolyte and weak alkali medium are 1.74×10^-44 cm²/s,2.21×10^-4cm²/s and 1.6×10^-77 cm²/s,respectively.the reversibility of Zn/Zn²⁺electrical pair can be improved by adding a high hydrogen evolution potential ion.When the zinc sheet is used as the negative electrode material of the liquid flow battery,the surface corrosion is severe,and the number of charge and discharge times increases,and the surface of the zinc sheet is severely corroded and exhibits different shapes.A chemically reduced graphene oxide（RGOT）electrode material with large voids,high strength and flexibility was prepared by the method of reducing GO by NaBH4.When chemical reduction graphene oxide（RGOC）was used as the working electrode,the diffusion coefficients of Ce³⁺and Fe²⁺were calculated to be 3.6x10^-5 cm²/s and 2.17×10^-6cm²/s,respectively.The electrochemically active RGOC reacted to the electrode is superior to RGOT,and RGOT is superior to GO.When different materials are used as the electrode material of the redox flow battery,in the charge-discharge process of Zn/Ce RFB,RGOC is used as the positive electrode,the coulombic efficiency reaches 89.6%,and the energy efficiency reaches 79.6%;during the charging and discharging process of Zn/Fe RFB,The charge and discharge capacity measured by RGOC is significantly higher than that of graphite felt,and the charge and discharge platform and coulombic efficiency are high.