Fe3+ and PO43- co-doped Li-rich Li1.20Mn0.56Ni0.16Co0.08O2 as cathode with outstanding structural stability for Lithium-ion battery

Abstract

The Li-rich Mn-based cathode materials exhibit great potential due to their ultrahigh specific capacity, but still suffer from low initial coulombic efficiency, inferior cycling stability, voltage decay and poor rate performance. In this study, we propose to enhance the structural stability and the electrochemical performances of Li1.20Mn0.56Ni0.16Co0.08O2 through the co-doping of Fe3+ and PO43-. The Fe3+ and PO43- are simultaneously doped in the precursor via a novel wet chemical method. In comparison with the undoped or mono-doped samples, the co-doped sample exhibits the best electrochemical performances owing to the synergistic effect of Fe3+ and PO43-, such as a high initial coulombic efficiency (88%), great cyclic stability (remains a specific capacity of 214 mAh g−1 after 130 cycles at 1 C) and mitigated voltage fade (2.12 mV per cycle). The synergistic mechanism of Fe3+ and PO43- is revealed based on X-ray diffraction, transmission electron microscope, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements. The co-doping of Fe3+ and PO43- constructs a stable oxygen-packed framework, which can alleviate lattice distortion, reduce the mixing of cations and increase the reversible reaction of 2 O2-/(O2)n-, contributing to outstanding structural stability. The synergetic strategy of anion and cation and the co-doping method in this work may provide some inspiration for designing the high-performance cathode materials of Lithium-ion battery.