Impact of the Surface on the Delithiation Mechanism of LiNi0.8Co0.15Al0.05O2 positive Electrodes for Li-Ion Batteries

Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
A. Grenier, H. Liu, K. M. Wiaderek, O. J. Borkiewicz, P. J. Chupas, and K. W. Chapman (Argonne National Laboratory)
The occurrence of an apparent two-phase delithiation mechanism reported for LiNi0.8Co0.15Al0.05O2 (NCA)is not intrinsic to the material but is due to a surface layer.

Ni-rich layered oxides like NCA are the most important class of positive electrodes for high-energy-density Li-ion batteries. These materials react with H2O and CO2 from air to form surface layers mainly composed of Li2CO32–5. The presence of such a surface layer is deleterious to the electrochemical performance of this class of material. We show, using in-situ synchrotron X-ray diffraction measurements, that this surface layer also induces the presence of a second phase during the 1st electrochemical delithiation. Such a mechanism is however not intrinsic to NCA. Indeed, a sample stored and handled in an argon atmosphere presents a typical solid solution behavior, as expected for this class of material.

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