Effects of Ag coating on the structural and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 as cathode material for lithium ion batteries

Abstract

Ni-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode materials are synthesized using Ni0.8Co0.1Mn0.1(OH)2 precursors obtained from a co-precipitation reaction and then coated with of metal Ag for the first time. X-ray diffraction results verify that Ag+ ions can hardly dope into the bulk NCM811 particles and the ion mixing degree of Li+/Ni2+ has been reduced. Amorphous Ag coating layers formed on the surface of Ag coated NCM811 materials are proved by scanning electron microscope and transmission electron microscope. X-ray photoelectron spectroscopy demonstrates that more Ni3+ ions on the surface of Ag coated NCM811 materials than that of pure NCM811. Galvanostatic charge-discharge tests indicate that 1 wt% Ag coated NCM811 exhibits initial discharge capacity of 209.1 mAh·g−1 and superior capacity retention of 90.5% after 90 cycles between 2.8 and 4.3 V, which shows greatly improved cycling stability compared with the pure NCM811 (87.9%). After Ag coating, reduced electrode polarization is certified by cyclic voltammetry, and better electron conductivity and higher Li+ diffusion coefficient are testified by electrochemical impedance spectroscopy. These results clearly indicate Ag coating can enhance the structural and electrochemical properties of NCM811 materials.