(95z) Stable Cyclic Performance of Li1.2Mn0.54Ni0.13Co0.13O2 Modified By Conductive CeO2 Film

Surface is imperative for electrode material in lithium ion battery. Formation of solid electrolyte interface (SEI) layer, and electrochemical and chemical reactions all start from surface. As a promising technique, atomic layer deposition (ALD) has been used to provide an initially safeguarding and uniform ultrathin film with a controllable thickness. In this work, CeO₂ was deposited by ALD with different thicknesses to modify the surface of lithium rich Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LRNMC) particles. The thickness was observed by transmission electron microscopy (TEM). At a condition of 1C rate and 55℃, the initial capacity of the electrode with an optimal thickness of coating exhibited 8% higher than 184 mAh/g of the uncoated LRNMC (UC) particles; there was still ~120 mAh/g retained after 400 cycles of charge/discharge, whereas only ~40 mAh/g for UC after 180 cycles of charge/discharge. A robust kinetic of electrochemical reaction was interpreted for the CeO₂ coated samples through electrochemical impedance spectroscopy (EIS). By applying AC and DC impedance spectra, conductivity of the coated samples was observed to be much higher than that of the UC at 60~140℃. CeO₂ thin coating increased conductivity of particles and blocked Mn²⁺ dissolution during charge/discharge cycling.