Sodium-ion storage behavior in carbon nanohorns in a diglyme-based electrolyte

The interaction behavior of solvated sodium ions in ether-based electrolytes with graphite electrodes via the co-intercalation mechanism captures wide research interest due to the remarkable reversible sodium-ion storage capacity, which cannot be achieved in ester-based electrolytes. However, the understanding of the sodium-ion storage mechanism and the structure-performance correlation is not fully established. This work aims to understand the origin of the unprecedented rate and cycling performance of sodium ions in diglyme solvent in carbon nanohorns with disordered graphitic domains and micropores. Ex-situ scanning electron microscope images reveal the formation of a uniformly thin solid electrolyte interphase on the surface of the carbon nanohorn electrode. The sodium-ion storage behavior is found to be closely related to the microstructure of the carbon nanohorns. In the diglyme-based electrolyte, the carbon nanohorn electrode displays a specific capacity of around 332 mA h g⁻¹ at the current density of 50 mA g⁻¹, along with good rate tolerance and stable cycling stability over 500 cycles. The enhanced electrochemical performance is further elucidated through galvanostatic intermittent titration technique (GITT), in-situ electrochemical impedance spectroscopy (EIS), and distribution relaxation time (DRT) analysis. To the best of our knowledge, this is the first study to understand sodium-ion storage behavior in carbon nanohorns.