Effect of Mg and Al cosubstitution on the structure and electrochemical performance of a Co-free LiNiO2 Mode material

A LiNiO2 cathode material was cosubstituted with Mg and Al to obtain LiNi0.90Mg0.05Al0.05O2 via solid-state sintering of a mixture containing stoichiometric amounts of Ni(OH)(2) precursor, LiOH center dot H2O, MgO, and Al2O3. The number of Li/Ni anti-site defects shown by X-ray diffraction was significantly reduced after cosubstitution of Mg and Al, and a 2-3 nm spinel-like structure was directly observed on the surface of LiNi0.90Mg0.05Al0.05O2 by Cs-corrected scanning transmission electron microscopy. This cosubstitution-induced structural modification enhanced the stability of the material during cycling. LiNi0.90Mg0.05Al0.05O2 half-cell showed an initial capacity of 210.8 mAh/g at 0.1 C (2.75-4.3 V) and excellent capacity retention of similar to 93.1% after 300 subsequent cycles at 1 C. In contrast, the bare LiNiO2 half-cell exhibited a capacity retention of only similar to 23.4% under the same cycling conditions, despite a high initial specific capacity of 238.1 mAh/g. Furthermore, the LiNi0.90Mg0.05Al0.05O2 half-cell also showed a much better rate performance than its bare LiNiO2 counterpart, with capacity retention levels at 5 C of 68.1% for the former and only 5.2% for the latter.