Rapid presodiation to improve the initial coulombic efficiency of an organic electrode material for sodium-ion batteries

Organic electrode materials are garnering increasing interest from academia as a potential negative electrode material for sodium-ion batteries (NIBs). Organic electrode materials offer unique advantages in comparison to inorganic materials as they can be derived from sustainable sources, such as biomass. However, their low initial coulombic efficiency (ICE) decreases energy density and cyclability. In a strategy designed to alleviate these issues, a presodiation technique with the reducing agent sodium biphenyl (NaBP) was used to improve the ICE of an organic electrode material, sodium naphthalene-2,6-dicarboxylate (Na₂NDC). Powder x-ray diffraction and Raman spectroscopy were employed to investigate the rapid sodiation procedure. Cyclic voltammetry and galvanostatic cycling elucidated the charge storage behavior. The addition of presodiation additive can be tuned to improve the ICE from 61% up to 150%. An improvement in the rate performance due to presodiation was demonstrated. This procedure can be applied to other organic electrode materials that suffer from low ICE in future investigations. Therefore, this methodology can assist in the adoption of organic electrode materials for NIB negative electrodes.