cm8b02720_si_001.pdf (3.6 MB)
Phase Evolution and Degradation Modes of R3̅m LixNi1–y–zCoyAlzO2 Electrodes Cycled Near Complete Delithiation
journal contribution
posted on 2018-10-09, 00:00 authored by Nicholas V. Faenza, Nathalie Pereira, David M. Halat, Julija Vinckeviciute, Lejandro Bruce, Maxwell D. Radin, Pinaki Mukherjee, Fadwa Badway, Anna Halajko, Frederic Cosandey, Clare P. Grey, Anton Van der Ven, Glenn G. AmatucciPractical
utilization of energy densities near the theoretical
limit for R3̅m layered oxide
positive electrode materials is dependent on the stability of the
electrochemical performance of these materials at or near full delithiation.
To develop new chemistries and novel approaches toward the improvement
of the electrochemical performance of these materials at such high
states of charge, a robust understanding of the failure mechanisms
limiting current materials is necessary. Thorough analysis of LixCo1–yAlyO2 and LixNi1–yAlyO2 as well as LixNi0.8Co0.2O2 and LixNi0.8Co0.15Al0.05O2 (1 ≥ x ≥ 0 and 0.2 ≥ y ≥ 0) enabled the identification of key relationships
between the transition metal chemistry of the electrode, its structural
stability, and cycling characteristics at or near complete delithiation
(4.75 V). Extensive characterization of these materials was achieved
by a multitude of physical and electrochemical techniques to investigate
the relative importance of surface vs bulk phenomena. The resulting
insights derived from these analyses highlight the importance of the
intrinsic structural and mechanical stability of the electrode when
highly delithiated and establish guidelines for identifying positive
electrode materials with improved high state of charge performance.
Particularly important is the contrasting electrochemical impact of
Al substitution into LiCoO2- and LiNiO2-based
materials, which is shown to likely arise from the enhanced propensity
for Al ions to migrate to the tetrahedral site in Co-rich compounds
at high states of delithiation.