The influence of Na2CO3 content and Ni2+ concentration on the physicochemical properties of nanometer Y-substituted nickel hydroxide

Nanometer Y-substituted nickel hydroxide was prepared by supersonic co-precipitation method with Na2CO3 as a buffer and NiCl2 as a nickel source. The crystal structure, morphology, particle size distribution and electrochemical performance affected by the buffer (Na2CO3) content and Ni2+ concentration are characterized. The results indicate most of the samples are co-existence with α and β phases and the proportion of α-Ni(OH)2 increases with the increase of Na2CO3, but decreases with the increase of Ni2+ concentration. The primary particles of samples are nanometer particles and the shape of primary particles transform from acicular to quasi-spherical with increasing Na2CO3 content, but converse process for the increase of Ni2+ concentration. The average particle size decreases initially and then increases. Complex electrodes were prepared by mixing 8 wt.% nickel hydroxides with commercial micro-size spherical nickel. The discharge capacities of samples increase initially and then decrease with increasing Na2CO3 content or decreasing Ni2+ concentration. When Na2CO3 content is 0.08 g and Ni2+ concentration is 0.2 mol/L, the sample has better electrochemical performance, such as larger discharge capacity (316.3 mAh/g at 0.2 C rate), lower charge voltage and higher discharge plateau, than those of other samples.