Research progress and prospect in element doping of lithium-rich layered oxides as cathode materials for lithium-ion batteries

At present, alpha-NaFeO2 lithium-rich layered oxides (LLO) as cathode materials for lithium-ion batteries have attracted widespread attention due to their structure and performance characteristics and have become the mainstream research materials for lithium-ion batteries. However, during the charge and discharge process, the irreversible phase transition, cation mixing, and oxygen loss on the surface will lead to the inevitable severe capacity attenuation. Aiming at these problems, researchers have carried out a lot of modification on the material to improve the electrochemical performances without changing the crystal structure. Element doping is one of the commonly used effective strategies. In this work, the recent progress in understanding the influences of dopants in LLO cathode materials were summarized through five types: dopants substituted for transition metal (TM), lithium, oxygen, respectively, and multiple-dopants, the element doping combined with other strategies. In addition, the development trend of element doping in LLO cathode materials was prospected. It is believed that this review can guide researchers on developing ion doping strategies for the LLO cathode materials.