| Project/Area Number |
10650826
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
無機工業化学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NAKAJIMA Tsuyoshi Kyoto University, Graduate School of Engineering, Associate Professor, 工学研究所, 助教授 (50026233)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Surface fluorination / Intercalation / Lithium ion battery / Carbon anode / フッ素化反応 |
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| Research Abstract |
Surface fluorination of graphite powder with average diameters, 7, 25 and 40 μm has been made by elemental fluorine at 80-520℃, and the electrochemical intercalation and deintercalation of lithium ion has been investigated in 1 mol dmィイD1-3ィエD1 LiClOィイD24ィエD2 ethylene carbonate/diethyl carbonate (1:1) solution. Fluorine contents were less than ca. 2 at% by elemental analysis and surface fluorine concentrations obtained by XPS were 6〜15 at%. Carbon-fluorine bonding is intermediate between the ionic and covalent, approaching the covalent bond with increasing fluorination temperature. Raman spectroscopy revealed that surface disorder is increased by fluorination. Graphite samples with average diameters 7, 25, 40 μm have the reversible capacities of 360, 350 and 330 mAhgィイD1-1ィエD1, respectively at 60 mAgィイD1-1ィエD1, however all the fluorinated samples have shown the larger capacities of 380〜400 mAhgィイD1-1ィエD1 than the theoretical value 372 mAhgィイD1-1ィエD1. The capacity and reaction rate increase would be due to increase in surface areas and formation of surface pores for lithium accumulation.
NMR study on C-F bonding has indicated that carbon-fluorine bond is ionic in the region of x>8 in CィイD2xィエD2F and semi-ionic nature increases with decreasing x. Addition of fluoroester and fluoroether to EC/DEC increases the reversible capacities of graphite electrode.
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