Synthesis of single-crystal magnesium-doped spinel lithium manganate and its applications for lithium-ion batteries

Single-crystal magnesium-doped spinel lithium manganate cathode materials are prepared by the hydrothermal method followed by the heat treatment. XRD patterns reveal that Mg2+ions have already diffused into the Li1.088Mn1.912O4 crystal structure and not affect the Fd3m space group. SEM images demonstrate that the magnesium-doped spinel lithium manganates show uniform polyhedral single crystals with 2–4 μm. Electrochemical performance demonstrates that the optimized composition of Li1.088Mg0.070Mn1.842O4 electrode exhibits the best electrochemical properties. It delivers 92.0 mAh g−1 at 8C rates and corresponds to 90.8% capacity retention (vs. 1C), far higher than those of the pristine electrode (70.4 mAh g−1 and 69.2%). In addition, the Li1.088Mg0.070Mn1.842O4 electrode also shows 95.5% capacity retention after 100 cycles at 1C, while the pristine electrode only shows 91.0% capacity retention. The excellent electrochemical performances of Li1.088Mg0.070Mn1.842O4 electrode are ascribed to the suppressed polarization, more stable crystal structure, and better kinetic characteristics.