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

Abstract

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 LiNi 0.49 Mn 1.49 Y 0.02 O 4-x F x (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. Y 3+ and F − co-doping led to the morphological evolution of LiNi 0.5 Mn 1.5 O 4 material. The introduction of Y 3+ and F − ions decreased the content of Mn 3+ 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 Y 3+ and F − co-doping, which can enhance the strength of crystal structure, resulting in better cyclic stability. The LiNi 0.49 Mn 1.49 Y 0.02 O 0.34 F 0.06 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. • A strategy for enhancing cycling stability of LNMO positive material is illustrated. • The morphological evolution of LiNi 0.5 Mn 1.5 O 4 materials. • The formation of microcrack can be suppressed by Y-F co-doping during cycles.