Carbon dots promoting surface defect and interphase high anion concentration for sodium-ion battery carbon anodes

The interphase chemistry of electrode/electrolyte significantly affects the electrochemical performance. This investigation explores the solid-liquid interphase alteration of an economical asphalt-derived carbon by incorporating multifunctional carbon dots, aiming to clarify the impact of interfacial properties on sodium-ion storage mechanisms. Enhanced by high density defects and carbonyl groups, the capacity, primarily within the sloping discharge, rise from 247 to 361 mA h g-1 in non-aqueous sodium ion batteries. Integrating experimental and computational methods reveals a marked improvement in PF6- anions absorption at the interface, refining the solvation structure and concentrating these anions. Consequently, a NaF/Na2CO3-dominated, inorganic-rich solid-electrolyte interphase (SEI) forms, attributed to the swift PF6- anion dissociation facilitated by the electrode's rapid electron mobility. This effect promotes sodium ion diffusion and accelerates the kinetics of sodium (de)intercalation. Beyond elucidating interfacial property contributions to the sodium storage in disordered carbon, this study highlights the genesis of irreversible capacity and draws connections between SEI's inorganic components and Coulombic efficiency. The insights offered furnish a pioneering perspective for engineering high-performance carbon anodes.