Effects of inorganic salts on the morphological, structural, and electrochemical properties of prepared nickel-rich Li[Ni0.6Co0.2Mn0.2]O2

The cathode active materials Li[Ni0.6Co0.2Mn0.2]O2 are synthesized using different inorganic salts, sulfate [NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O], nitrate [M(NO3)2·6H2O (M = Ni, Co, Mn)] and acetate [M(CH3COO)2·4H2O (M = Ni, Co, Mn)]. The X-ray diffraction (XRD) patterns indicate that sulfate and nitrate starting materials formed a well-ordered hexagonal α-NaFeO2 layered structure (space group: 166, R3¯m). However, acetate starting material is led to a poorly layered structure compared to the other materials. Field emission scanning electron microscope (FE-SEM) images show that sulfate and acetate starting materials formed nano-sized primary particles with a size of about 200-500 nm and 300 nm, and void channels. However, the primary particles with a size of 300 nm from nitrate starting material agglomerate together to form micro-sized secondary particles. The initial discharge capacities of the sulfate, nitrate, and acetate starting materials are 138.3, 142.4, and 135.9 mAh g−1 at 1 C-rate in the voltage range 3.0-4.3 V vs. Li/Li+, respectively. The discharge capacity retentions of sulfate, nitrate, and acetate starting materials are 92.5%, 63.9%, and 78.1% at 1 C-rate after 50 cycles, and 83.2%, 48.0%, and 71.7% at 6 C-rate after 100 cycles, respectively.