A Miss Is as Good as a Mile: Prediction of Additive Effectiveness in Sodium-Ion Batteries Based on Electrostatic Potential

Electrolyte additives are essential for sodium-ion batteries (SIBs), yet their design based on lithium-ion battery (LIB) principles has limitations. Notably, certain hallmark additives in LIBs, despite their proven effectiveness, fail in SIBs due to unclear mechanisms. This study reveals the critical role of reduced-state structures and electrostatic potential (ESP) distributions in predicting additive behavior. Using vinylene carbonate as a model, we demonstrate that even minor ESP variations can lead to divergent reduction pathways, forming detrimental sodium ethene glycol-like product (NED) in SIBs versus beneficial polycarbonate (LVDC) in LIBs. Furthermore, we establish that ESP similarities can effectively predict additive performance, explaining why fluorinated ethylene carbonate and trans-difluoroethylene carbonate exhibit distinct behaviors in SIBs. Beyond enabling rapid screening of LIB additives for SIB applications, our findings highlight how subtle differences in electrolyte microstructure can profoundly impact interphasial chemistry, underscoring the need for deeper investigations into electrolyte design.