High capacity 0.5Li2MnO3·0.5LiNi0.33Co0.33Mn0.33O2 cathode material via a fast co-precipitation method

Solid solution material of 0.5Li2MnO3·0.5LiNi0.33Co0.33Mn0.33O2 (alternatively Li[Li0.2Mn0.54Ni0.13Co0.13]O2) was synthesized by a fast co-precipitation method which takes sulfates with high solubility as the transition metal sources of mixed hydroxide precursor. The optimal synthetic conditions were determined through the design of orthogonal experiments. The properties of samples synthesized under the best conditions were investigated in detail. The XRD pattern of 0.5Li2MnO3·0.5LiNi0.33Co0.33Mn0.33O2 revealed a well ordered hexagonal layered structure with the evident feature of super lattice caused by Li2MnO3. FESEM images showed that the powders possess small and unagglomerated particles with size range of 100–300 nm. XPS analysis results demonstrated that the valence states of Ni, Co, Mn are +2, +3, and +3.52 respectively. The electrochemical measurements showed that the optimal material delivers initial discharge capacity of 315.3 mAh g−1 at 1/20 C between 2.0 and 4.8 V with good cycle stability after firstly several cycles. CV test proved that the high capacity performance is ascribed to the redox of oxygen or its species at the electrode surface. Rate test showed that 179.5 mAh g−1 was obtained at 2 C which is considerably high, as far as we concerned.