The effect of fluorides in the TiO2(B) anode on the hydrogen evolution reaction in aqueous electrolytes

Aqueous lithium-ion batteries (A-LIBs) have become an exciting field of research due to their potential for sustainable energy storage. However, one major challenge they face is the hydrogen evolution reaction (HER), which occurs when water molecules in the electrolyte split into protons and electrons at the anode. This reaction competes with the primary electrochemical processes of the anode, resulting in capacity loss and reduced cycling stability. Understanding and mitigating HER is crucial for improving the performance and longevity of A-LIBs.

To tackle the HER challenge, researchers explored the use of fluorine-based additives in anodes. Fluorine is a highly reactive element that can form stable and hydrophobic layers on the surface of materials. By incorporating these additives into the TiO2(B) anode, researchers aimed to reduce the reactivity of the water molecules and slow down the HER process.

In this study, researchers synthesized and incorporated three distinct fluorine-based additives into the TiO2(B) anode: aluminum fluoride (AlF3), lithium fluoride (LiF), and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS). The FAS containing anodes demonstrated the highest HER delay with the smallest amount of additives due to its hydrophobic nature. This innovation has the potential to expand the energy density and improve the operational stability of A-LIBs.

The researchers found that the FAS containing anodes delayed the onset of HER by 45–160mV compared to the bare TiO2(B) anode. This delay is significant because it means that the anode can withstand more charge-discharge cycles without experiencing capacity loss and reduced stability. The results underscore the potential of fluorine-based passivation layers in mitigating the HER.

The discovery of fluorine-based passivation layers has significant implications for the development of sustainable energy storage technologies. By mitigating the HER challenge, A-LIBs can achieve higher energy densities and improved operational stability. This innovation paves the way for the broader application of A-LIBs in various fields, including renewable energy systems, electric vehicles, and grid-scale energy storage.