TY - JOUR
T1 - Thermal stability of LixCoO2 cathode for lithium ion battery
AU - Baba, Yasunori
AU - Okada, Shigeto
AU - Yamaki, Jun ichi
N1 - Funding Information:
The authors wish to thank Rigaku for the measurement of high-temperature X-ray diffraction, and Mitsubishi Heavy Industries, for financial support.
Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2002/6
Y1 - 2002/6
N2 - It is well known that charged Lix)CoO2 (x < 1) is metastable, and that oxygen evolution has been observed at temperatures above 200 °C. LixCoO2, delithiated by a chemical method using H2SO4, was investigated by means of differential scanning calorimetry (DSC) with/without an electrolyte (1 M LiPF6/ethylene carbonate (EC) + dimethyl carbonate (DMC)). The lithium content x in the delithiated LixCoO2 was determined by atomic absorption spectroscopy. The DSC profile of Li0.49CoO2 showed two exothermic peaks, one beginning at 190 °C and the other beginning at 290 °C. From high-temperature X-ray diffraction (XRD), it was found that the first peak, from 190 °C, was the phase transition from a monoclinic (R3̄m) to a spinel structure (Fd3m). The DSC measurements of Li0.49CoO2 with the electrolyte at various mixing ratios showed two exothermic peaks, one beginning at 190 °C and the other at 230 °C. The exothermic heat of each peak was proportional to the amount of Li0.49CoO2. The peak starting at 190 °C probably resulted from the decomposition of solvent due to an active cathode surface, and the peak starting at 230 °C was electrolyte oxidation caused by released oxygen from Li0.49CoO2. The exothermic heat from 190 to 230 °C based on cathode weight was 420 ± 120 J/g, and that from 230 to 300 °C was 1000 ± 250 J/g.
AB - It is well known that charged Lix)CoO2 (x < 1) is metastable, and that oxygen evolution has been observed at temperatures above 200 °C. LixCoO2, delithiated by a chemical method using H2SO4, was investigated by means of differential scanning calorimetry (DSC) with/without an electrolyte (1 M LiPF6/ethylene carbonate (EC) + dimethyl carbonate (DMC)). The lithium content x in the delithiated LixCoO2 was determined by atomic absorption spectroscopy. The DSC profile of Li0.49CoO2 showed two exothermic peaks, one beginning at 190 °C and the other beginning at 290 °C. From high-temperature X-ray diffraction (XRD), it was found that the first peak, from 190 °C, was the phase transition from a monoclinic (R3̄m) to a spinel structure (Fd3m). The DSC measurements of Li0.49CoO2 with the electrolyte at various mixing ratios showed two exothermic peaks, one beginning at 190 °C and the other at 230 °C. The exothermic heat of each peak was proportional to the amount of Li0.49CoO2. The peak starting at 190 °C probably resulted from the decomposition of solvent due to an active cathode surface, and the peak starting at 230 °C was electrolyte oxidation caused by released oxygen from Li0.49CoO2. The exothermic heat from 190 to 230 °C based on cathode weight was 420 ± 120 J/g, and that from 230 to 300 °C was 1000 ± 250 J/g.
UR - http://www.scopus.com/inward/record.url?scp=0036604238&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036604238&partnerID=8YFLogxK
U2 - 10.1016/S0167-2738(02)00067-X
DO - 10.1016/S0167-2738(02)00067-X
M3 - Article
AN - SCOPUS:0036604238
VL - 148
SP - 311
EP - 316
JO - Solid State Ionics
JF - Solid State Ionics
SN - 0167-2738
IS - 3-4
ER -