Spherical Ni0 Research Articles

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

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.

Synthesis the Precursor of LiNi<sub>0.5</sub>Mn<sub>0.5</sub>O<sub>2</sub> via an Improved Carbonate Co-Precipitation

Spherical Ni0.5Mn0.5CO3 is synthesized via carbonate co-precipitation method which uses NH4HCO3 as the precipitator. However, obvious agglomerate of secondary particles occurs when NH4HCO3 is used as the precipitator. The agglomerate particles can result in inferior physical characteristic. An improved carbonate co-precipitation which used NH4HCO3 doped with different proportion of NaOH as a new precipitator is tested in our study. Observed by SEM and Mastersizer, spherical morphology with narrow particle size distribution is synthesized with the proportion of NaOH reaches 10%. The element line analysis by Electron Probe Micro-analyzer shows symmetrical distributions of Ni and Mn elements via the improved carbonate co-precipitation.