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Exploring the Kinetic Limitations Causing Unusual Low-Voltage Li Reinsertion in Either Layered or Tridimensional Li2IrO3 Cathode Materials
journal contribution
posted on 2020-02-24, 20:10 authored by Biao Li, Gaurav Assat, Paul E. Pearce, Victoria A. Nikitina, Antonella Iadecola, Charles Delacourt, Jean-Marie TarasconThe
α- and β-Li2IrO3 polymorphs
were recently studied in view of their anionic redox capabilities
that were triggered by full Li removal. Herein, we solely focused
on the reacting mechanism involved during the first reversible Li
removal (Li2IrO3 → LiIrO3).
We found that the charge and discharge processes show significant
deviations from the equilibrium potential especially with the appearance
of a peculiar low-voltage feature during discharge with increasing
the discharge current. Through detailed electrochemical experiments,
such as rate dependence and relaxation, we show that this feature
is associated with a kinetically limited phase transition behavior.
Moreover, we demonstrated that the large voltage hysteresis pertaining
to the removal and uptake of one Li from Li2IrO3 is nested in a different way that the biphasic transition proceeds
between charge and discharge, as deduced by operando X-ray diffraction.
Additionally, electroanalytical measurements coupled with scanning
electron microscopy unveils that the sluggish biphasic transition
is rooted in the slow diffusion of Li+ ion together with
the existence of high nucleation barrier of the biphasic reaction.
Finally, the similarities and differences between the kinetics limitations
in both Li2IrO3 polymorphs are then discussed
with respect to the similar type of limitations occasionally encountered
in conventional layered oxides and other cathodes.