Effect of boric acid on the properties of Li_2MnO_3LiNi_(0.5)Mn_(0.5)O_2 composite cathode powders prepared by large-scale spray pyrolysis with droplet classifier

摘要

Spherically shaped 0.3Li_2MnO_3-0.7LiNi_(0.5)Mn_(0.5)O_2 composite cathode powders with filled morphology and narrow size distribution are prepared by large-scale spray pyrolysis. A droplet classification reduces the standard deviation of the size distribution of the composite cathode powders. Addition of boric acid improves the morphological properties of the product powders by forming a lithium borate glass material with low melting temperature. The optimum amount of boric acid dissolved in the spray solution is 0.8 wt% of the composite powders. The powders prepared from the spray solution with 0.8 wt% boric acid have a mixed layered crystal structure comprising Li_2MnO_3 and LiNi_(0.5)Mn_(0.5)O_2 phases, thus forming a composite compound. The initial charge and discharge capacities of the composite cathode powders prepared from the 0.8 wt% boric acid spray solution are 297 and 217mAh g~(-1), respectively. The discharge capacity of the powders decreases from 217 to 196 mAh g~(-1) by the 30th cycle, in which the capacity retention is 90%.