Mechanochemical Modification of Oxygen/Nitrogen Species on Surface of Hard Carbon for Improved Sodium Storage

Abstract

Oxygen and nitrogen are common but efficient heteroatoms for carbon materials to enhance electronic conductivity and electrochemical reactivity. The carbon−oxygen and carbon−nitrogen bonds are significant for the electrochemical performance of the doped carbon. Among these, CO groups and pyridinic-N have been widely recognized as the most active adsorption sites for Na + . In this work, the percentages of active O/N species on the surface have been regulated by a mechanochemical approach. The high content of CO groups along with pyridinic-N can be achieved in N-doped carbon nanospheres (NCS). NCS as an anode thus delivers a capacity of 281.6 mA h g −1 at 0.03 A g −1 after 120 cycles, which is enhanced by 75.1% in comparison to the untreated sample. It retains 134.9 mA h g −1 at 1 A g −1 up to 2000 cycles. The enhanced sodium storage properties are created by plentiful sodium adsorption sites, including CO groups and defects, and good electronic conductivity induced by pyridinic-N. The present work should supply a reference for adjusting heteroatoms on carbonaceous materials and their application in the energy storage field.

Directional modification of oxygen functional groups by N heteroatoms on soft/hard carbons for sodium storage

“…The reason for the improved performance of N-HC is that the N doping not only changes the electron distribution and electronic conductivity, but also introduces more defects and creates additional active sites. 14 As expected, N-SC exhibits the greatest rate capability with reversible capacities of 249, 215, 197, 179, 169, and 157 mA h g −1 obtained at 0.05–2 A g −1 , respectively. N-SC has the highest content of CO groups, which greatly promote the adsorption of Na + and storage capacity.…”

“…1,2 It has been proved that N doping has an effect on the content of oxygen and the formation of OFGs on the surface of HC by mechanochemical and thermochemical methods. 13,14 But there have been fewer investigations on oxygen functionalization of SC during N doping. Therefore, selecting representative carbon materials (SC and HC) as research objects and observing the evolutions of OFGs during N doping have a universal value for investigation and application in the fields of batteries, supercapacitors, and even electrocatalysis.…”

Highly efficient utilization of sodium storage sites for MOF-derived carbon by rapid carbonization

“…12 As shown in Table S1 (ESI†), the absolute content of N element for Co/NC- x ( x = 5, 10, 30, 60) decreases continuously from 24.9 at% to 15.3 at% with carbonization time. With the carbonization proceeding to 60 min, Co/NC-60 shows the lowest content of the active N species (Pyri-N and Pyrr-N), since a portion of them is converted to Grap-N 13 and a portion escapes in the form of gas. Importantly, the oxygen functionalization process also changes after carbonation.…”