Facile Redox Synthesis of Layered LiNi1/3Co1/3Mn1/3O2 for Rechargeable Li-ion Batteries

The present work reports on the development of layered-type Lix(Ni1/3Co1/3Mn1/3)O2 (x = 1.05 and 1.1) cathodes by a simple ambient temperature redox synthesis followed by post-heat treatments with added lithium source. The intermediate precursor (Ni1/3Co1/3Mn1/3Oy) was synthesized through redox reaction between KMnO4, CoCl2 and NiCl2 in aqueous KOH medium. Synchrotron XANES and ICP measurements were performed to confirm the changes in the oxidation states and successful control in stoichiometric ratio of ternary transition metal oxide (Ni2+0.33Co3+0.35Mn4+0.32Oy) during the redox reaction. Synchrotron X-ray diffraction studies of post lithiation confirmed the formation of a well-developed layer-type hexagonal phase of α-NaFeO2 with least cation mixing, as observed from the estimated lattice parameters (a = 2.858 Å and c = 14.228 Å), integrated intensity ratio (I003/I104 = 1.79), and c/3a ratio (∼1.659) values. FE-SEM images revealed loosely agglomerated particles with average diameters of 60 nm in the intermediate product while the particle-size grows to a few hundred nanometers after lithiation at elevated temperatures. The electrochemical performances in the potential range of 3.0-4.3 V vs. Li/Li+ at 14 mAg−1 indicated that reasonable specific capacities and cycle performances are registered for all the prepared cathodes. In particular, the Li1.05(Ni1/3Co1/3Mn1/3)O2 composition demonstrated the highest capacity retention value (∼99%) after 50 cycles and better rate performances (104, 91, 76, and 67 mAhg−1) at high current densities (229, 457, 914, and 1429 mAg−1 respectively).