Operando magnetic susceptibility measurements on the cathode material during repetitive electrochemical cycling were performed, enabling a continuous and bulk sensitive monitoring of the charge compensation process. Upon charging and Li extraction down to the Li contents of x = 1/3, exclusively Ni undergoes oxidation in two consecutive steps, namely, for x > 2/3 and for 2/3 > x > 1/3 with a continuous transition in between. In the regime of low Li concentrations x < 1∕3, both Co- and O-ions contribute to the charge compensation. While the oxidation of Ni and O during charging is reversible, the Co oxidation is found to be irreversible.
Continuous monitoring of the bulk oxidation states in during charging and discharging
G. Klinser, S. Topolovec, H. Kren, S. Koller, W. Goessler, H. Krenn, R. Würschum; Continuous monitoring of the bulk oxidation states in during charging and discharging. Appl. Phys. Lett. 21 November 2016; 109 (21): 213901. https://doi.org/10.1063/1.4968547
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