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 (LiNi 1-x-y Mn x Co y O 2 ) and NCA (LiNi 1-x-y Co x Al y O 2 ) become more and more Ni-rich, they approach LiNiO 2 . Therefore it is important to benchmark the structure and electrochemistry of state of the art Li x NiO 2 for the convenience of researchers in the field. In this work, LiNiO 2 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 Li x NiO 2 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.