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

Abstract

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-Al2O3-coated LiMn2O4 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-Al2O3 layer tightly coupling with the surface of the LiMn2O4 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 Al2O3-coating content). Moreover, the ICP-AES tests of Mn2+ reveal that the Al2O3 layers with two step coating layer plays an important role in protecting LiMn2O4 from the electrolyte corrosion.