Synthesis of Zirconium-Based Material-Coated LiNi_(0.8)Co_(0.2)O_2 Cathode Using a New Coating Method

摘要

Zr-compound-coated LiNi_(0.8)Co_(0.2)O_2 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 LiNi_(0.8)Co_(0.2)O_2 are dissolved in the water phase. In a flame, precursors in the water phase transform into LiNi_(0.8)Co_(0.2)O_2 core particles and the Zr precursor in the oil phase transforms into a coating layer on the LiNi_(0.8)Co_(0.2)O_2 surface. After Zr compound coating, both the electrochemical performance and cycle stability are enhanced because the Zr compound coating layer prevents the oxidation of Ni~(3+) of LiNi_(0.8)Co_(0.2)O_2 by acidic electrolyte. Since the Zr compound material is coated to prevent the Li_2CO_3 formation on the LiNi_(0.8)Co_(0.2)O_2 surface, the effectiveness of the Zr compound coating in preventing Li_2CO_3 formation is investigated. After the as-prepared Zr-compound-coated LiNi_(0.8)Co_(0.2)O_2 particles and bare LiNi_(0.8)Co_(0.2)O_2 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 Li_2CO_3 formation.