Organic acid assisted solid-state synthesis of Li1.2Ni0.16Co0.08Mn0.56O2 nanoparticles as lithium ion battery cathodes

Lithium-rich layered oxide Li1.2Ni0.16Co0.08Mn0.56O2 can be referred as a crystalline mixture of Li2MnO3 and LiNi0.4Co0.2Mn0.4O2 at equal molar ratio. In the paper, the solid state reaction of M(AC)2·4H2O (M = Mn, Co and Ni) and LiOH·H2O has been performed to obtain nanocrystalline Li1.2Ni0.16Co0.08Mn0.56O2 using a small molecular organic acid (i.e., oxalic acid (OA), citric acid (CA) or tartaric acid (TA)) as additive. The introduction of organic acids can help to improve the layered structure and inhibit the particle growth of Li1.2Ni0.16Co0.08Mn0.56O2, and the different organic acids exert distinct influences on the structural and electrochemical properties of Li1.2Ni0.16Co0.08Mn0.56O2. In detail, the nanoparticles obtained in the presence of OA have the smallest average size of 50–150 nm, which correspondingly exhibit the highest initial discharge capacity of 267.52 mAh g−1 at 0.1C and the best high-rate capability (e.g., 152.22 mAh g−1, 5C) when applied as a lithium ion battery cathode. Furthermore, the active substance obtained from TA shows the best cycling stability and a discharge capacity of 202.42 mAh g−1 can be retained after 50 cycles at 0.5C.