Halogenated Functional Electrolyte Additive for Li-CO₂ Batteries

In recent years, functional electrolyte additives have been widely studied during the CO₂ evolution reaction (CO₂ER) and CO₂ reduction reaction (CO₂RR) processes for Li-CO₂ batteries. Owing to different concerns, functions of these additives are also multiple and limited. In this work, the multiple impacts of functional electrolyte additives for Li-CO₂ batteries are discussed. N-phenylpyrrolidine (PPD) and 1-(3-bromophenyl) pyrrole (Br-PPD) are investigated as additives successively. First, the corresponding charging potential during the CO₂ER process can be reduced to 3.65 V with PPD; then the Li||Li symmetric cells with Br-PPD possess a superior long-term cycling of 800 h benefited from a stable solid electrolyte interphase (SEI) on the surface of a Li metal by using a Li anode protected with bromine functional groups. In Br-PPD-based Li-CO₂ cells, the charging potential can be maintained at 3.70 V for 120 cycles even with a Super P cathode. In this work, the relationship between the structural properties of organic molecules and their electrochemical applications is discussed and investigated. This is essential for the targeted design and preparation of additives in rechargeable batteries.