Understanding the Influence of Surface Oxygen Groups on the Electrochemical Behavior of Porous Carbons as Anodes for Lithium-Ion Batteries

Abstract

The present study elucidates the role of surface oxygen functional groups on the electrochemical behavior of porous carbons when used as anodes for Li-ion batteries. To achieve this objective, a carbon xerogel (CX) obtained by pyrolysis of a resorcinol-formaldehyde gel was modified by different post-synthesis treatments in order to modulate its surface chemistry while maintaining its external surface constant. Various surface modifications were obtained by oxidation in air, insitu polymerization of dopamine and, finally, by grafting of a polyethylene oxide layer on the polydopamine coating. While oxidation in air did not affect the pore texture of the CX, modifications by coating techniques substantially decreased the micropore fraction. Detailed electrochemical characterizations of the materials processed as electrodes were performed by capacitance measurements and galvanostatic cycling. Surface chemistry results, by X-ray photoelectron spectroscopy, show that the accessibility and the capacity increase when carbonyl (R-C=O) groups are formed on the CX, but not with oxides and hydroxyls. The amount of surface carbonyls, and in particular aldehyde (O=CH) groups, is found as the key parameter since it is directly correlated with the modified CX electrochemical behavior. Overall, the explored surface coatings tend to reduce the micropore volume and add mainly hydroxyl functional groups but hardly change the Li + insertion/de-insertion capacities, while oxidation in air adds carbonyl groups, increasing the Li + ions storage capacity thanks to an improved accessibility to the carbon network, which is not caused by any textural change.

Hydrothermal Activation of Porous Nitrogen-Doped Carbon Materials for Electrochemical Capacitors and Sodium-Ion Batteries

“…Our results agree well with previously reported data that the increased concentration of nitrogen, mainly pyridinic form, is one of the reasons for improving Na-ion storage capacity [14,15,18]. Piedboeuf et al found that among the oxygen-containing functionalities only carbonyl groups resulted in the increased storage capacity of Li + ions [93]. That also is in accordance with our results.…”

Design of Hierarchical NiCo2O4 Nanocages with Excellent Electrocatalytic Dynamic for Enhanced Methanol Oxidation

“…C-O=C at a binding energy of 530.5 eV corresponded to the high number of defect sites containing low oxygen coordination [20]. O=C at a binding energy of 531.7 eV could be ascribed to the multiplicity of physisorbed water at and within the surface [17,21]. The results of XPS demonstrated a mixed valence containing Co 2+ , Co 3+ , Ni 2+ and Ni 3+ , which was consistent with previous reports [22].…”

Carbon Nanocluster‐Mediated Nanoblending Assembly for Binder‐Free Energy Storage Electrodes with High Capacities and Enhanced Charge Transfer Kinetics

“…This result was consistent with previous reports on oxygen‐functionalized carbon materials in Li cells. [ 53,54 ] Thus, the CCNs exhibited a substantially higher specific capacity of ≈420 mAh g −1 compared to nonfunctionalized CNs (≈197 mAh g −1 ) with a double‐layer capacitance‐based Li storage mechanism. Additionally, to better understand the electrolyte‐derived surface layer, the differential capacity vs. potential profiles of the electrodes were plotted from the 5 th GCD cycle at a current density of 0.1 A g −1 (Figure 2c).…”