Grant-in-Aid for Scientific Research (A)
|Allocation Type||Single-year Grants |
|Research Institution||KYUSHU UNIVERSITY |
OKADA Shigeto Kyushu Univ., Institute for Materials Chemistry and Engineering, Associate Professor, 先導物質化学研究所, 助教授 (10304841)
YAMAKI Jun-ichi Kyushu Univ., Institute for Materials Chemistry and Engineering, Professor, 先導物質化学研究所, 教授 (70294981)
EGASHIRA Minato Yamaguchi Univ., Department of Applied Chemistry and Chemical Engineering, Associate Professor, 工学部, 助教授 (20304842)
|Project Period (FY)
2002 – 2004
Completed (Fiscal Year 2004)
|Budget Amount *help
¥45,240,000 (Direct Cost: ¥34,800,000、Indirect Cost: ¥10,440,000)
Fiscal Year 2004: ¥5,980,000 (Direct Cost: ¥4,600,000、Indirect Cost: ¥1,380,000)
Fiscal Year 2003: ¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000)
Fiscal Year 2002: ¥33,020,000 (Direct Cost: ¥25,400,000、Indirect Cost: ¥7,620,000)
|Keywords||Lithium-ion battery / Cathode active material / Intercalation / Host compound|
Our research of realize low-cost and high-energy density post Li-ion batteries for EV use can be summarized as follows;
1)New synthesis process for iron phosphate :
a)High temperature melting synthesis for LiFePO_4 :
In order to use low reactive iron oxide as starting material, FeO was melted with P_2O_5 and LiOH-H_2O at 1500 ℃ for a few minutes and cooled in an Ar atmosphere. The slow-cooled sample with 140 mAh/g shows a similar profile to solid-state synthesized olivine LiFePO_4, though the quenched amorphous sample shows a monotonically decreasing discharge profile with poor capacity.
b)Low temperature soft chemistry method for FePO_4 :
In the use of low cost iron powder as a starting material, metallic iron powder and P_2O_5 were reacted in water at room temperature. The highest capacity obtained by annealing at 500 ℃ was 153 mAh/g.
We could obtained LiVP_2O_7 andTiP_2O_7 as new compounds. They show both M^<2+>/M^<3+> and M^<3+>/M^<4+> redox reactions on charge/discharge cycle. Moreover, (MoO_2)_2P_2O_7 shows the largest reversible capacity (150 mAh/g) as a cathode fur Na battery.
We synthesized the calcite-type iron borate (FeBO_3) as polyanionic anode with higher capacity than that of graphite. In order to reduce the voltage, the redox couple replacement from Fe to V or Ti could be done successfully.
We could synthesized the single-phase Li_2CoSiO_4. The theoretical capacity of the olivine-type silicate is two times larger than that of the olivine-type phosphate such as LiFePO_4.
As a new fluorophosphate system, single phase Li_2CoPO_4F could be obtained by solid-state synthesis method and the structure was identified by neutron diffraction. The theoretical capacity is two times larger than that of LiFePO_4 and the cell voltage is 4.8 V.versus Li.