Optimized Synthetic Conditions of LiNi0.5Co0.2Mn0.3O2 Cathode Materials for High Rate Lithium Batteries via Co-Precipitation Method

Abstract

A synthetic condition for LiNi0.5Co0.2Mn0.3O2 cathode materials to improve their rate capability and elevated temperature performance at 60°C was optimized with Ni0.5Co0.2Mn0.3(OH)2 precursors prepared using a co-precipitation method. Under conditions of pH = 11, NH3/MSO4 = 0.8, and stirring speed = 1000 rpm, spherical Ni0.5Co0.2Mn0.3(OH)2 precursors with a tap density of 2.2 gcm−3 and particle size of 7μm were successfully obtained. Using these optimized precursors, LiNi0.5Co0.2Mn0.3O2 material (denoted as LU3) with an average particle size and tap density of 7 μm and 2.6 gcm−3, respectively, was prepared and electrochemical performances at 23°C and 60°C were characterized. The first discharge capacity of the optimized sample was 204 mAh/g with a coulombic efficiency of 92% at 0.1C rate in a lithium half-cell between 3 and 4.5V. Further, it maintained 50% capacity retention (electrode density of 2.9 gcc−1) at a 7C rate, while a commercial sample showed only 37% (electrode density of 2.6 gcc−1) at the same rate under electrode. In other words, the LU3 cathode delivered specific energy of 380 Wh/kg under specific power of 290W/kg, while a CS cathode delivers only specific energy of 206 Wh/kg under power of 220W/kg. At 60°C, the LU3 sample had higher capacity retention than the commercial one. XPS and TEM results of the samples after cycling showed that distribution of Ni atoms on the surface played a key role in sustaining the structural stability during the cycling.