Piedboeuf Marie-Laure C, Job Nathalie, Aqil Abdelhafid, Busby Yan, Fierro Vanessa, Celzard Alain, Detrembleur Christophe, Léonard Alexandre F
University of Liège, Department of Chemical Engineering-Nanomaterials, Catalysis, Electrochemistry (NCE)-B6a, Sart-Tilman, B-4000 Liège, Belgium.
Center for Education and Research on Macromolecules (CERM)-B6a, University of Liège, Sart-Tilman, B-4000 Liège, Belgium.
ACS Appl Mater Interfaces. 2020 Aug 12;12(32):36054-36065. doi: 10.1021/acsami.0c08297. Epub 2020 Jul 31.
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 postsynthesis treatments in order to modulate its surface chemistry while maintaining its external surface constant. Various surface modifications were obtained by oxidation in air, 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, from 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 to be the key parameter because 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/deinsertion capacities, while oxidation in air adds carbonyl groups, increasing the Li ion storage capacity, thanks to an improved accessibility to the carbon network, which is not caused by any textural change.
本研究阐明了表面氧官能团在多孔碳用作锂离子电池阳极时的电化学行为中所起的作用。为实现这一目标，通过间苯二酚 - 甲醛凝胶热解得到的碳干凝胶（CX），经过不同的后合成处理进行改性，以调节其表面化学性质，同时保持其外部表面不变。通过在空气中氧化、多巴胺聚合，以及最后在聚多巴胺涂层上接枝聚环氧乙烷层，获得了各种表面改性。虽然在空气中氧化不影响CX的孔结构，但通过涂层技术进行的改性显著降低了微孔分数。通过电容测量和恒电流循环对作为电极处理的材料进行了详细的电化学表征。X射线光电子能谱的表面化学结果表明，当CX上形成羰基（R - C═O）基团时，可及性和容量会增加，但形成氧化物和羟基时则不会。发现表面羰基的量，特别是醛基（O═CH）基团的量是关键参数，因为它与改性CX的电化学行为直接相关。总体而言，所探索的表面涂层倾向于减少微孔体积并主要添加羟基官能团，但几乎不改变锂的嵌入/脱出容量，而在空气中氧化会添加羰基，由于改善了对碳网络的可及性，增加了锂离子存储容量，这并非由任何结构变化引起。
