Surface Modification of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂Cathode Material with Al₂O₃/SiO₂Composite for Lithium-Ion Batteries

Lithium-rich layered oxide Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 is synthesized by solid phase method and followed by surface modification with 2 wt% nAl 2 O 3 /SiO 2 (n means the molar ratio of Al 2 O 3 and SiO 2 ). The morphology, structure and electrochemical properties of the material samples before and after coating treatment are systematically investigated by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, linear sweeping voltammetry, potentiostatic intermittent titration and electrochemical impedance spectroscopy. The results show that a protective multilayer is formed on the material particle surface with a new coating layer like Li x [Al y Si z O 4 ] and an intermediate layer with lithium-deficient disordered spinel structure after annealing treatment. This multilayer can prevent the material from corrosion of the electrolyte deposition product, provide improved lithium ion transportation and suppress the evolution from layered structure to spinel. The coated samples present the improved initial coulombic efficiency, capacity retention, cycling stability, rate capability and reduced voltage decay compared to the pristine material and it delivers the best comprehensive electrochemical performance when the molar ratio of Al 2 O 3 and SiO 2 is 2:1. The main role of Al 2 O 3 and SiO 2 in coating for the improvements of the material performance is further discussed.