Improved Electrochemical Performance of Al(OH)3-coated LiCoO2 Cathode Materials at severe conditions

Abstract

Recently, layered Li[NixCo1-xMnx]O2 materials have been promoted as cathode materials with higher energy density to replace LiCoO2 in Li-ion batteries. In response to this pressure, substantial efforts have been made to increase the specific capacity of LiCoO2 by using a wide range cutoff potential(~4.5V) without other electrochemical defects, especially in capacity retention. For example, many other research groups had reported that metal oxide coated LiCoO2 have a highly improved electrochemical performances at a higher upper cutoff potential(~4.5V). But there are many difference opinions about why the improved performance is occurred. Someone have been insisting that metal oxide coating is prevent the structural defect at higher potential, but another says that the improved performance is derived only by using surface refreshing. In this work, we attempted to coat LiCoO2 with metal hydroxide and oxide form. The Al(OH)3 coated LiCoO2 had the highest electrochemical performances and excellent capacity retention, which results are owing to prevent dissolution of transition metals and unwanted reactions between cathode and electrolyte. Electrochemical properties of the various cathode materials were characterized by means of galvanostatic charge/discharge test(3.5~4.5V).