Influence of Electrolyte Additives on the Corrosion Behavior of Current Collectors for Lithium-Sulfur Batteries

Lithium–sulfur (Li–S) batteries are promising next-generation energy storage systems, offering higher energy density than conventional lithium-ion batteries, making them ideal for use in electric vehicles and portable electronics. A crucial design challenge is the corrosion of current collectors, which can significantly influence the performance and lifespan of a Li–S battery. Understanding and mitigating this corrosion are key to improving the durability of Li–S batteries. This study investigates the galvanic corrosion of aluminum (Al) and copper (Cu) current collectors in the presence of electrolyte additives, specifically triethyl phosphate (TEP) and bis(2,2,2-trifluoroethyl) ether (BTFE), using potentiodynamic polarization studies, electrochemical impedance spectroscopy (EIS), and surface characterization through XPS, FTIR, and FESEM. The electrochemical and morphological results show that the additive molecules are adsorbed on the surface of the current collectors via weak ionic interaction and promote the formation of a protective passivation layer on the surface, significantly enhancing corrosion resistance. This study proposes the corrosion mechanism of Al and Cu current collectors in the presence of the TEP and BTFE electrolyte additives. The interaction of BTFE through F δ− with Cu 2+ /Al 3+ on the surface of current collectors facilitate the formation of a stable passivation layer. BTFE exhibits a low corrosion rate in both the current collectors, even after a period of three months, making it suitable for long-term applications. XPS peaks corresponding to Al–F, Al–O, and C–F confirm the contribution of additive on the surface layer of current collectors. Fluorine-based additives, such as BTFE, are preferable for mitigating corrosion on both aluminum and copper current collectors over extended periods.