Active Organic Salts Enabling Non-Intrusive Electrolyte Presodiation Strategy

Abstract

Na-ion batteries show great promise, but their practical utilization is hindered by irreversible Na-ion loss during cell formation, resulting in initial coulombic efficiencies typically below 80%. Conventional presodiation methods, which involve solid additives in the cathode, can compromise electrode integrity and leave deteriorated residues, especially with high Na ion compensation (20%). An electrolyte presodiation approach is introduced that utilizes sodium thiocyanate (NaSCN) as an electrolyte additive, discovered through cheminformatics and machine learning. This organic salt decomposes at 3.3–4.0 V, releasing active Na ions and forming a cosolvent without damaging the electrode and the cell, as confirmed by spectroscopic and microscopic analyses. The method improves the initial coulombic efficiency of a hard carbon|P2-Na_2/3Ni_1/3Mn_1/3Ti_1/3O₂ pouch cell from 80.8% to 95.2%, with a capacity retention of 84.5% over 400 cycles. These findings present a practical and non-intrusive way to address Na-ion deficiency challenges in Na-ion batteries.