The action of Y-F co-doping in LiNi0.5Mn1.5O4 positive electrode materials

The addition of either yttrium or fluorine has been reported to enhance electrochemical properties of spinel layered cathode material. In this work, pristine and Y-F co-doped LiNi0.49Mn1.49Y0.02O4-xFx (x = 0.02, 0.04, 0.06) spinel powders were synthesized by a citric acid aided route. The correlation between structural, morphological and electrochemical properties of all four cathodic materials was systematically studied. Y3+ and F− co-doping led to the morphological evolution of LiNi0.5Mn1.5O4 material. The introduction of Y3+ and F− ions decreased the content of Mn3+ ions and lattice volume, which can alleviate the Jahn-Teller distortion and maintain the stability of spinel structure. The predominantly disordered of Y-F co-doped samples exhibited better rate capability. Moreover, the formation of microcracks within Y-F co-doped sample can be suppressed during cycles by Y3+ and F− co-doping, which can enhance the strength of crystal structure, resulting in better cyclic stability. The LiNi0.49Mn1.49Y0.02O0.34F0.06 LNMO sample exhibited optimal electrochemical properties, delivering a discharge capacity of 136.044 mAh g−1 after 200 cycles at 1C with superior retention of 96.8%, and the specific capacity reaching 102.030 mAh g−1 at 5C. The synergistic influence of crystalline structure and morphology on electrochemical properties shows that Y-F co-doping has a positive impact on rate capability and cycling stability of LNMO materials.