Synthesis of Zirconium-Based Material-Coated LiNi0.8Co0.2O2 Cathode Using a New Coating Method

Zr-compound-coated LiNi0.8Co0.2O2 is prepared in a single step using a new powder coating process, a modified flame spray pyrolysis method using a water-in-oil emulsion precursor solution. Only the Zr precursor is dissolved in the oil phase and the precursors of LiNi0.8Co0.2O2 are dissolved in the water phase. In a flame, precursors in the water phase transform into LiNi0.8Co0.2O2 core particles and the Zr precursor in the oil phase transforms into a coating layer on the LiNi0.8Co0.2O2 surface. After Zr compound coating, both the electrochemical performance and cycle stability are enhanced because the Zr compound coating layer prevents the oxidation of Ni3+ of LiNi0.8Co0.2O2 by acidic electrolyte. Since the Zr compound material is coated to prevent the Li2CO3 formation on the LiNi0.8Co0.2O2 surface, the effectiveness of the Zr compound coating in preventing Li2CO3 formation is investigated. After the as-prepared Zr-compound-coated LiNi0.8Co0.2O2 particles and bare LiNi0.8Co0.2O2 particles were exposed in an air for a month, the changes in morphologies and structures before and after aging were observed by using thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is confirmed that Zr compound coating effectively reduces the amount of Li2CO3 formation. (C) 2012 The Japan Society of Applied Physics