Updating the Structure and Electrochemistry of Li_xNiO₂ for 0 ≤ x ≤ 1

Ni-rich transition metal layered oxide materials are of great interest as positive electrode materials for lithium ion batteries. As the popular electrode materials NMC (LiNi1-x-yMnxCoyO2) and NCA (LiNi1-x-yCoxAlyO2) become more and more Ni-rich, they approach LiNiO2. Therefore it is important to benchmark the structure and electrochemistry of state of the art LixNiO2 for the convenience of researchers in the field. In this work, LiNiO2 synthesized from a commercial Ni(OH)2 precursor and modern synthesis methods shows a specific capacity close to the theoretical specific capacity of 274 mAh/g. In-situ X-ray diffraction (XRD) measurements were conducted to obtain accurate structural information versus lithium content, x. The known multiple phase transitions of LixNiO2 during charge and discharge were clearly observed, and the variation in unit cell lattice constants and volume was measured. Differential capacity versus voltage (dQ/dV vs. V) studies were used to investigate the electrochemical properties including regions of composition that show very slow kinetics. It is hoped that this work will be a useful reference for those working on Ni-rich positive electrode materials for Li-ion cells.