Fig. 5: Analysis of defects-related sodium storage properties of AC, CMS-800, and CMS-1300 negative electrodes.
From: Redefining closed pores in carbons by solvation structures for enhanced sodium storage
a Raman spectra of the three carbon negative electrodes in their original state, after aging, and after the first cycle. The D-band, situated at around 1350 cm−1, originates from sp2 carbon atoms in rings at defects. The G-band, located at around 1580 cm−1, originates from aromatic sp2 carbon atoms. b, c Operando Raman spectra of three carbon negative electrodes during the initial discharge/charge in the region centered on b G-band and c D-band. The transition point from discharge to charge is labeled by dashed lines. The discharge/charge process was performed at 25 °C using specific current of 50 mA g−1. d Calculated model of Na+ absorbed in various kinds of defects based on DFT, along with e the optimized structure of NaC7.5 and sequential difference of energy as a function of the number of Na+ adsorbed. Source data are provided as a Source Data file.
