Many investigations of high potential cathodes in lithium systems have shown evidence of oxygen evolution, which can lead to thermal runaway problems. It will be shown that this is to be expected on the basis of thermodynamic considerations. Experiments involving 10 phases in the Li-Co-O, Li-Fe-O and Li-Mn-O systems were performed in a glove box over a limited range of both oxygen pressure and voltage, and the results interpreted in terms of ternary phase stability diagrams. They showed a linear relation between the logarithm of the equilibrium oxygen pressure and the potential, independent of both the chemical compositions and the crystal structures of the phases involved. Extrapolation to higher potentials indicates very high values of the equilibrium oxygen pressures in high voltage cathode materials. These results show that the critical issue related to the equilibrium oxygen pressure of high potential cathodes is their potential, not their compositions or crystal structures.
[1]
Yi Cui,et al.
Investigations of the Electrochemical Stability of Aqueous Electrolytes for Lithium Battery Applications
,
2010
.
[2]
P. Ruetschi.
Silver-silver sulfate reference electrodes for lead-acid batteries
,
2003
.
[3]
Cause of the memory effect in “nickel” electrodes
,
2007
.
[4]
P. Ruetschi,et al.
Anodic Oxidation of Lead at Constant Potential
,
1964
.
[5]
P. Ruetschi,et al.
Ion Selectivity and Diffusion Potentials in Corrosion Layers Films on Pb in
,
1973
.
[6]
Robert A. Huggins,et al.
Mechanism of the memory effect in “Nickel” electrodes
,
2006
.
[7]
R. Huggins,et al.
Relationships among electrochemical, thermodynamic, and oxygen potential quantities in lithium-transition metal-oxygen molten salt cells
,
1984
.