Synthesis and electrochemical performance of Ni and F doped LiMn2O4 cathode materials

Abstract

A series of Ni and F ion doped LiMn₂O₄ composite cathode materials are synthesized via a sol–gel method with citric acid as the chelating agent. The morphology and structure of LiNi_xMn_2−xO_4−yF_y were characterized by XRD, SEM, EDS and the electrochemical performance was tested and characterized by CV and EIS. The results showed that Ni and F ions were uniformly dispersed in the lattice without changing the structure and morphology of LiMn₂O₄. LiNi_0.03Mn_1.97O_3.95F_0.05 exhibits an excellent electrochemical performance among all the samples, and delivers an initial discharge capacity of 120.3 mA h g⁻¹ at 1C and with a retention of 94.5% (25 °C) and 80.4% (55 °C) after the 100th cycle respectively. The results demonstrated that the dual-doping of Ni and F ions in lithium manganate can prevent the manganate from dissolving in the electrolyte and enhance the cycling performance at elevated temperatures, exhibiting excellent performance at different discharge rates.