Electrochemical and Kinetic Studies of
Li1.156Mn1.844O4
Zonghai Chen and K. Amine
Chemical Engineering Division, Argonne National Laboratory, Argonne,
Illinois 60439, USA
Abstract
The electrochemical and kinetic properties of a lithium-rich spinel material,
Li1.156Mn1.844O4, were investigated to illustrate the impact of the excessive
lithium on the performance of spinel-based lithium-ion cells. It was found that
the capacity retention of such mesocarbon microbead/spinel cells was
significantly deteriorated when the upper cutoff voltage was raised from 4.1 to
4.3 V at 55°C. The significant difference on the capacity retention was
attributed to the irreversible reaction at about 4.22 V, which was further
related to the electrochemical reaction of lithium-rich spinel at high voltages.
The low rate cycling of Li/spinel cells at different temperatures showed the
evolution of at least three irreversible peaks above 4.2 V. Moreover, the Li/spinel
cells showed continuous impedance growth after extraction of the excessive
lithium. The kinetic study showed that the irreversible peaks shifted toward low
potential as the temperature increased. It is predicted that the first
irreversible peak shows up at about 4.25 V vs Li/Li+ at 55°C. It suggests that
the upper cutoff voltage of such graphite/spinel cells should be limited to 4.1
V at 55°C. The kinetic study also indicates that such graphite/spinel cells can
be cycled up to 4.4 V at 25°C without triggering any detrimental impact.
©2006 The Electrochemical Society
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