抄録
In lithium–oxygen batteries (LOBs), the chemical stability of electrolyte solvents is a critical factor determining cell performance. While sulfonamides represent a promising class of solvents for LOB electrolytes, systematic investigations into the structure–stability relationship of their analogs remain limited. In particular, although reactions involving the α-hydrogen (i.e., hydrogen abstraction and/or deprotonation of the hydrogen atom α to the sulfonyl group) have been widely considered to be initiating steps of solvent decomposition in various electrolytes, their actual impact on solvent decomposition and subsequent battery performance remain unclear. In this study, we performed a comparative analysis to elucidate the structure–stability relationships of sulfonamides with the general structure R1–SO2–NCH3(C4H9). Differential electrochemical mass spectrometry (DEMS) measurements revealed that the presence of α-hydrogens is not the dominant factor in solvent decomposition. Instead, the decomposition of the N-alkyl (butyl) chain plays a major role. These results suggest that longer alkyl chains lower the corresponding C–H bond dissociation energies through stabilization of the resulting alkyl radicals, thereby enhancing susceptibility to hydrogen abstraction by reactive oxygen species generated during the discharge/charge process. Our findings indicate that considering only the presence or absence of α-hydrogens is insufficient for designing chemically stable solvents. Rather, minimizing the number of C–H bonds susceptible to hydrogen abstraction is crucial for improving solvent stability.
