Ni-rich LiNi0.905Co0.043Al0.052O2 cathode material for high-energy density Li-ion cells: Tuning lithium content, structural evolution, and full-cell performance

Abstract

Ni-rich LiNi0.905Co0.043Al0.052O2 oxides with the Li excess (x) up to 7 mol.% used in the synthesis are prepared by a facile dry-mixing method. It is shown that the Li/Ni mixing level and crystallite size are dependent on the Li amount, while Al from the precursor acts as a scavenger of the excessive Li. Operando X-ray diffraction (XRD) studies enable explaining differences in the structural evolution of materials exhibiting high and low Li/Ni mixing, especially in the H2↔H3 transition region. Soft X-ray absorption spectroscopy (XAS) studies show differences in the charge state evolution of the surface and bulk Ni. The optimized oxide with the Li excess x = 2 mol.% delivers excellent electrochemical performance, with an initial discharge capacity of 205.5 mAh g−1 at 0.1C, and 91.4 % capacity retention after 100 cycles at 1C. The unmodified in any other way cathode material allows achieving the discharge capacity of 178.5 mAh g−1 at the high rate of 5C, and works well in the full-cells.