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

Abstract

Different oxygen functionalization processes occur for N-doped soft carbon (N-SC) and hard carbon (N-HC), and there may be a competitive relationship between the formation of pyridinic-N and C=O groups. For...

The structural changes and sodium storage in the carbon phase of cobalt sulfide/carbon composites

“…30 Notably, the absolute content of carbonyl groups improved from 1.9 at% (HC) to 5.2 at% (Co 4 S 3 –HC) since the C atoms near defects have higher reactivity and electron-donating ability and hence serve as active centers that increase oxygen affinity and facilitate the improvement of oxygen level. 46 Nevertheless, the absolute content of carboxyl groups decreased from 3.3 at% (HC) to 1.2 at% (Co 4 S 3 –HC). This may happen because the carboxyl groups are reduced to carbonyl groups and the C–O bonds in the carboxyl groups are weakened in the presence of transition metals, resulting in lower activation energy for the deoxygenation reaction and the eventual removal of the –OH bonds.…”

“…The connection between current (i) and scan rate (n) is given by the formula i = av b . 35,46 Fig. 4(c) displays the relationship between log(i) and log(v) at different peaks (1-4) with slopes (b value) 0.65, 0.73, 0.68 and 0.75, respectively, which demonstrate the coexistence of diffusion and surface capacitive contributions.…”

Directional Regulation of Surface Chemistry of Graphene Using Carbon Dots for Sodium-Ion Battery Anodes

“…The 0.4 CDs/rGO displays a capacity of 116 mAh g –1 and a capacity retention of 81.2% after 2000 cycles (Figure d). The high reversible capacity of 0.4 CDs/rGO at 2.0 A g –1 is ascribed to the abundant CO groups and edge defects that benefit rapid Na storage. , Additionally, through the same calcination process at 250 °C, the rate performance of CDs was evaluated, and the corresponding result is shown in Figure S9. The poor rate performance of the CDs is owing to the lesser conductivity due to the excessive oxygen content and poor degree of graphitization.…”

Sulfur Encapsulation and Sulfur Doping Synergistically Enhance Sodium Ion Storage in Microporous Carbon Anodes

“…Current research has already proved that carbon materials with pseudocapacitive properties can store Na + through the reversible adsorption process of Faraday capacitance. − Rapid sodium storage of materials can be realized by pseudocapacitive characteristics, leading to materials with excellent rate performance that would meet the market of fast charging and discharging. − Notably, doping heteroatoms into carbon materials can not only effectively enhance the pseudocapacitance of the materials but also adjust the surface wettability and electronic conductivity, thereby promoting charge transfer and improving the interaction between electrodes and electrolytes. Up to now, various heteroatom-doped carbon-based anode materials have been extensively studied and applied in SIBs. − The commonly used heteroatoms in carbon materials are nitrogen, sulfur, , oxygen, phosphorus, − and other elements . Since the covalent radius is similar to that of carbon, nitrogen can be doped to create more defects in carbon materials and increase electronic conductivity.…”