EPR, NMR, and Electrochemical Studies of Surface-Modified Carbon Microbeads
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- 作者：Ricardo Alcá ; ntara ; Gregorio F. Ortiz ; Pedro Lavela ; José ; L. Tirado ; Radostina Stoyanova ; and Ekaterina Zhecheva
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：May 2, 2006
- 年：2006
- 卷：18
- 期：9
- 页码：2293 - 2301
- 全文大小：189K
- 年卷期：v.18,no.9(May 2, 2006)
- ISSN：1520-5002
文摘
Nongraphitic carbon microbeads were prepared by hydrothermal treatment of a glucose aqueous solutionat 180 
C. Impregnation of glucose-derived carbon microbeads with citric acid was used to control themicrobeads' surface and electrochemical properties. The microspherical sample thus obtained exhibiteda highly disordered nanocrystalline structure and a low BET surface area. The electrochemical performanceof carbon microbeads was evaluated from discharge/charge experiments in lithium and sodium cells, aswell as from electrochemical impedance spectroscopy measurements. The intercalation of Li and Na insurface-modified carbon microbeads was explored by EPR and NMR spectroscopy. It was shown thatsimilar mechanisms operate for lithium and sodium insertion into disordered carbons. The observed Curie-like behavior and the change in intensity of the EPR signals as a function of cell voltage agreed wellwith lithium insertion into different sites of disordered carbon structures forming paramagnetic centers.Microspherical carbon samples with high reversible capacities in both Li and Na cells commonly exhibitlow concentrations of paramagnetic centers.
C. Impregnation of glucose-derived carbon microbeads with citric acid was used to control themicrobeads' surface and electrochemical properties. The microspherical sample thus obtained exhibiteda highly disordered nanocrystalline structure and a low BET surface area. The electrochemical performanceof carbon microbeads was evaluated from discharge/charge experiments in lithium and sodium cells, aswell as from electrochemical impedance spectroscopy measurements. The intercalation of Li and Na insurface-modified carbon microbeads was explored by EPR and NMR spectroscopy. It was shown thatsimilar mechanisms operate for lithium and sodium insertion into disordered carbons. The observed Curie-like behavior and the change in intensity of the EPR signals as a function of cell voltage agreed wellwith lithium insertion into different sites of disordered carbon structures forming paramagnetic centers.Microspherical carbon samples with high reversible capacities in both Li and Na cells commonly exhibitlow concentrations of paramagnetic centers.