Carboxyl‐Dominant Oxygen Rich Carbon for Improved Sodium Ion Storage: Synergistic Enhancement of Adsorption and Intercalation Mechanisms
Fei Sun, Hua Wang, Zhibin Qu, Kunfang Wang, Lijie Wang, Jihui Gao, Jihui Gao, Jianmin Gao, Jianmin Gao, Shaoqin Liu, Yunfeng Lu
Abstract
Abstract Oxygen‐containing groups in carbon materials have been shown to affect the carbon anode performance of sodium ion batteries; however, precise identification of the correlation between specific oxygen specie and Na + storage behavior still remains challenging as various oxygen groups coexist in the carbon framework. Herein, a postengineering method via a mechanochemistry process is developed to achieve accurate doping of (20.12 at%) carboxyl groups in a carbon framework. The constructed carbon anode delivers all‐round improvements in Na + storage properties in terms of a large reversible capacity (382 mAg −1 at 30 mA g −1 ), an excellent rate capability (153 mAg −1 at 2 A g −1 ) as well as good cycling stability (141 mAg −1 after 2000 cycles at 1.5 A g −1 ). Control experiments, kinetic analysis, density functional theory calculations, and operando measurements collectively demonstrate that carboxyl groups not only act as active sites for Na + capacitive adsorption through suitable electrostatic interactions, but also gradually expand d ‐spacing by inducing a repulsive force between carbon layers with Na + preadsorbed, and hence facilitate diffusion‐controlled Na + insertion process. This work provides a new insight in the rational tunning of oxygen‐containing groups in carbon for boosting reversible Na + storage through a synergy of adsorption and intercalation processes.