Effect of TiO₂ Layer Thickness on Electrode Degradation in Redox Flow Batteries

In this work, TiO2 coatings of various thicknesses were deposited on carbon felt fibers using the ALD (Atomic Layer Deposition) method, and the mechanical and electrochemical properties of the electrodes were studied. The experimental results show that the TiO2 coating effectively protects and enhances the stability of carbon wet electrodes. While a mass loss of 4% was observed in the untreated cathode electrode, this figure decreased to 1.6-1.7% when a TiO2 coating was applied. When the coating thickness was increased from 50 nm to 300 nm, no significant change in mass loss was observed, which indicates that even thin coatings provide effective protection. The mass loss in the anode electrode was relatively small, ranging from 2% in the untreated state and 0.5-1.1% in the coated states. This is explained by the lower anode potential than the cathode and the low sensitivity of the V2+/V3+ redox reaction at the anode. It was found that the titanium dioxide coating plays an important role in increasing the electrochemical degradation and corrosion resistance of the electrodes, as well as in extending the battery life. It was also shown that a 50 nm thick TiO2 coating can provide effective protection, while very thick coatings can limit electron mobility. These results confirm that TiO2 coatings are one of the promising solutions for protecting electrode materials in vanadium flow batteries.

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