Preparation of porous spherical α-Ni(OH) 2 and enhancement of high-temperature electrochemical performances through yttrium addition

Abstract

Through homogeneous precipitation method, uniform spherical α-Ni(OH) 2 particles were obtained at appreciate aging time in urea solution without any help of templates or dispersants. From SEM images, aging time exhibited great effects on the morphology of as-synthesized α-Ni(OH) 2. Also, long aging time helped to improve the electrochemical performances of α-Ni(OH) 2. It was found that the proper aging time was 12 h. However, α-Ni(OH) 2 showed low charge/discharge capacities at high temperatures. Therefore, yttrium was added to improve the high-temperature electrochemical performances of α-Ni(OH) 2. The influences of doping ratios of Y on the morphologic and high-temperature electrochemical characteristics were investigated through XRD, SEM, TEM, constant current charge/discharge, and cyclic voltammetric measurements. The α-Ni(OH) 2 samples with the addition of about 5.8 mol% Y showed a discharge capacity of 250 mAh/g at 0.2 C rate and 60 °C, much higher than that of α-Ni(OH) 2 without Y dopants (157 mAh/g).