Highly stable nickel-rich cathode materials LiNi0.90Co0.05Mn0.05O2 with Mn concentration gradient for lithium-ion batteries

Ni-rich layered cathode materials (LiNixCoyMn1-x-yO2) have attracted much attention due to their high energy density and environmentally friendly advantages. However, the capacity fading and structural instability with the increase of Ni content are still the main problems restricting the commercialization of high nickel cathodes. In this paper, the method of co-precipitation and calcination is used to prepare LiNi0.90Co0.05Mn0.05O2 (CG-NCM5) with Mn concentration gradient, which the Ni content is decreasing from the core to the outer of CG-NCM5, while the Mn content is increasing. The CG-NCM5 has less Li/Ni mixing and a good layered structure. More importantly, the Mn-rich outer plays a key role in preventing the appearance of microcracks and enhancing the structure stability, because it can effectively suppress the volume change stemming from the phase transition during charge/discharge process. Meanwhile, the low Ni on the surface reduces the highly reactive Ni4+ that easily reacts with electrolyte, mitigates material surface degradation and accelerates lithium-ion transport. Therefore, it exhibits a superior reversible capacity of 191.4 mAh/gat 1C and a capacity retention of 83.7 % after 200 cycles in 2.7–4.3 V. These results indicate that Mn concentration gradient materials may provide a practical approach to highly stable nickel-rich cathode materials for lithium-ion batteries.