二价与四价金属离子等摩尔共掺杂的锂离子电池正极材料LiMn1.9Mg0.05Ti0.05O4的制备与表征

An Mg(II) and Ti(IV), iso-molar, co-doped cathode material Li Mn1.9Mg0.05Ti0.05O4 for lithium-ion batteries was successfully synthesized via a sol-gel method, using lithium hydroxide, manganese acetate, magnesium nitrate, and butyl titanate as raw materials, and citric acid as a chelating agent. The as-prepared materials were characterized using thermogravimetric analysis(TGA), X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and electrochemical tests(including cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS) measurements). The results demonstrated that the cathode material Li Mn1.9Mg0.05Ti0.05O4, which was obtained after calcination at 780 °C for 12 h, exhibited a fine microstructure and good electrochemical performance. When cycled at 4.35-3.30 V at room temperature,Li Mn1.9Mg0.05Ti0.05O4 delivered a discharge specific capacity of 126.8 m Ah·g-1at 0.5C rate, and maintained a capacity of 118.5 m Ah·g-1after 50 cycles; the capacity retention of this material reached 93.5%. This material showed a discharge-specific capacity of 111.9 m Ah·g-1at 0.5C rate after 30 cycles, when it was cycled at 55 °C;under these conditions the capacity retention reached 91.9%, far superior to the capacity retention of undoped Li Mn2O4. The iso-molar co-doping of Li Mn2O4 with Mg(II) and Ti(IV) ions led to significant modification of the electronic and ionic conductivity, and increased the rate properties and electrochemical performance of the spinel lithium manganate at elevated temperatures.