Chemically\nActive Sulfonate Additive with Transition\nMetal and Oxygen Dual-Site Deactivation for High-Voltage LiCoO<sub>2</sub>

Modulating a solid electrolyte interphase (SEI) through\nadditives\nrepresents a crucial approach for stable operation of cathode materials.\nTraditional perspectives focus on the electrochemical decomposition\nof the additive itself while underestimating the reactivity and catalytic\nability from cathode surfaces. Inspired by the sulfur-containing species\ncausing catalyst poisoning, the catalytic effects of LiCoO<sub>2</sub> (LCO) for the sulfur-based molecule (−SO<sub><i>x</i></sub>) additives have been investigated. We elucidate the mechanism\nof additives by assessing multiple interactions with the LCO surface,\nwhich are primarily characterized by chemical ring-opening reactions.\nFurthermore, decreasing the saturated carbon in molecules can enhance\nits reactivity, while the −SO<sub><i>x</i></sub> groups\ndeactivate both the lattice oxygen and transition metal center through\ndual-site bond formation. Benefiting from the chemically passivated\nsurface, the sulfonate additive enables LCO cycling at a high temperature\nand a high voltage of 4.65 V. This provides new insights into the\nmechanisms for stabilizing the cathode interface and molecular design\nfor additives.