Suppression of structural phase transformation of Li-rich Mn-based layered cathode materials with Na ion substitution strategy

Abstract

Li-rich Mn-based layered cathode materials are subjected to unsatisfactory cycle stability, rate performance and voltage fading from the undesirable structure evolution during cycling despite its ultrahigh specific capacity. In this paper, Na-doped Li1.15Na0.05[Mn0.54Ni0.13Co0.13]O2 is prepared via introducing larger ionic radius Na ion into the lithium layer of the Li-rich layered cathode material via co-precipitation and high temperature soild-state reaction method. As prepared Na-doped cathode exhibits excellent electrochemical performances, including initial discharge capacity as high as 281 mAh g−1 at 0.1 C and good rate capacity with reversible discharge capacity of 142 mAh g−1 at 5 C. Furthermore, the Na ion substitution substantially suppresses the occurrence of Li+/Ni2+ mixing and phase transformation of layered Li-rich Mn-based oxide materials during continuous cycling, stabilizing the host layered structure. Higher capacity retention of 93.4% can be maintained on Na-doped cathode material after 100 cycles at 1 C rate compared with the undoped cathode (86.3%). Besides, the Na ion substitution also effectively reduces the internal charge transfer impedance and promotes the Li-ion diffusion kinetics, manifesting a promising cathode alternative for new-generation Li-ion battery benefiting from the outstanding performances and simple procedure.