Facile synthesis of LiMn2O4 microsheets with porous micro-nanostructure as high-rate cathode materials for Li-ion batteries

摘要

Porous LiMn2O4 microsheets with micro-nanostructure have been successfully prepared through a simple carbon gel-combustion process with a microporous membrane as hard template. The crystal structure, morphology, chemical composition, and surface analysis of the as-obtained LiMn2O4 microsheets are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscope (XPS). It can be found that the as-prepared LiMn2O4 sample presents the two-dimensional (2-D) sheet structure with porous structure comprised with nano-scaled particles. As cathode materials for lithium-ion batteries, the obtained LiMn2O4 microsheets show superior rate capacities and cycling performance at various charge/discharge rates. The LiMn2O4 microsheets exhibit a higher charge and discharge capacity of 137.0 and 134.7 mAh g(-1) in the first cycle at 0.5 C, and it remains 127.6 mAh g(-1) after 50 cycles, which accounts for 94.7% discharge capacity retention. Even at 10 C rate, the electrode also delivers the discharge capacity of 91.0 mAh g(-1) after 300 cycles (93.5% capacity retention). The superior electrochemical properties of the LiMn2O4 microsheets could be attributed to the unique microsheets with porous micro-nanostructure, more active sites of the Li-ions insertion/deinsertion for the higher contact area between the LiMn2O4 nano-scaled particles and the electrolyte, and better kinetic properties, suggesting the applications of the sample in high-power lithium-ion batteries.