A Wide-Temperature-Range, Low-Cost, Fluorine-Free Battery Electrolyte Based On Sodium Bis(Oxalate)Borate

Common battery electrolytes comprise organic carbonate solvents and fluorinated salts based on hexafluorophosphate (PF6–) anions. However, these suffer from high flammability, limited operating temperature window, cost. To address those issues, we here propose a fluorine-free electrolyte sodium bis(oxalate)borate (NaBOB). Although lithium (LiBOB) has previously been investigated for lithium-ion batteries, NaBOB was considered too insoluble in to be used practice. Here, show that can dissolved mixtures of N-methyl-2-pyrrolidone (NMP) trimethyl phosphate (TMP) each sole solvent. NMP provides higher solubility with concentration almost 0.7 M, resulting an ionic conductivity up 8.83 mS cm–1 at room temperature. The physical electrochemical properties salt TMP their binary are investigated. results include the thermal behavior mixtures, flammability tests, solubility, measurements mixtures. Full-cell sodium-ion batteries hard carbon anodes Prussian white cathodes were evaluated 55 °C using aforementioned electrolytes. much improved performance compared conventional 1 M NaPF6 currents elevated temperatures. proposed provide wide range ?60 as NMP–TMP have low freezing points. tests indicate nonflammable when contains more than 30 vol % TMP.