Spinel LiMn2O4 with Two-step Nano-Al2O3 Coating as High Performance Positive Materials

To study the influence of the uniformity and integrity of amphoteric metal oxide coating layers on the performance of positive materials in Lithium-ion batteries, nano-Al 2 O 3 -coated LiMn 2 O 4 positive material were synthesized by using a two-step sol-gel process. The products were characterized by power X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), energy-dispersive X-ray spectrum (EDX), X-ray photoelectron spectroscopy ( XPS), galvanostatic charge-discharge test system, and inductively-coupled plasma emission spectrograph (ICP-AES). The results show that the two step method coating can bring with the uniform and glabrous nano-Al 2 O 3 layer tightly coupling with the surface of the LiMn 2 O 4 particles, when being positive material for Lithium-ion batteries, which exhibits capcity losses of only 13.2 % at 60 °C, after 300 cycles, much better than those of the pristine material and the sample synthesized by conventional one step sol-gel method (with the same Al 2 O 3 -coating content). Moreover, the ICP-AES tests of Mn 2+ reveal that the Al 2 O 3 layers with two step coating layer plays an important role in protecting LiMn 2 O 4 from the electrolyte corrosion.