Branched Diamine Electrolytes for Na⁺-Solvent Cointercalation into Graphite

Recently, graphite has been recognized as a potential negative electrode for sodium (Na)-ion batteries via the use of a solvent cointercalation mechanism. However, nearly all works exploring this mechanism have focused on glymes, which are stable for reversible cointercalation. Herein, we demonstrate branched diamines, such as 1,3-diaminopentane, as alternative cointercalating solvents showing initial capacities up to 130 mAh/g for graphite in Na cells. X-ray diffraction indicated a reversible and smaller expansion of the lattice compared to glymes, which nearly doubles the volumetric capacity. In all, our work indicates some appealing characteristics when amine electrolytes are cointercalated into graphite.