Ammonia-low coprecipitation synthesis of lithium layered oxide cathode material for high-performance battery

Abstract

The ammonia-low hydroxide coprecipitation process has successfully synthesized Ni0.6Co0.2Mn0.2(OH)2 precursor by replacing ammonia with NH4+ and lowering the pH of the salt solution with acid. NH4+ and H+ increase the diffusion range of the salt solution and both react with OH−, which would reduce the nucleation rate and increase the complexation under low ammonia concentration conditions. The optimal pH of coprecipitation is determined from the theoretical calculation on the competitive relationship between complexation (Me(NH3)n2+) and precipitation (OH−) using chemical equilibrium and solubility product constant. And compared with other different complexing agents (e.g., NH4+, H+, and NH3), the material obtained with both NH4+ and H+ has the optimized particle morphology, size, composition, and element distribution. The resulting LiNi0.6Co0.2Mn0.2O2 cathode material exhibits superior electrochemical properties, when compared to a commercial sample, with a high initial discharge capacity (176.6 mAh g−1), cycling stability (91.9% retention for 100 cycles), and rate capability (115.7 mAh g−1 at 3C). Moreover, it also demonstrates excellent electrochemical performance in lithium-ion full batteries matched with commercial graphite or Si/C anodes. Ammonia-low coprecipitation synthesis would greatly reduce the treatment cost of production wastewater, improve the working environment of operators, and protect the natural ecological environment of the earth.