Synthesis, characterization and electrochemical performance of high-density aluminum substituted α-nickel hydroxide cathode material for nickel-based rechargeable batteries

Positive electrode active materials, AI-substituted alpha-Ni(OH)(2), with a high tap-density and high performance for alkaline nickel-based rechargeable batteries have successfully been synthesized using a polyacrylamide (PAM) assisted two-step drying method and subsequent hydrothermal treatment at 140 degrees C for 2 h. X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), laser particle size analysis, tap-density measurement, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge test are used to characterize the physical and electrochemical properties of the synthesized material. The tap-density of the resulting powders reaches 1.84 g cm(-3), which is significantly higher than that of alpha-Ni(OH)(2) powders obtained by the conventional co-precipitation (CCP) and hydrothermal (HT) methods. Compared with commercial spherical beta-Ni(OH)(2), the resulting sample is electrochemically more active, providing discharge capacities of 315.0 and 255.2 mAh g(-1), and volume capacities of 579.6 and 469.6 mAh cm(-3) at rates of 0.2 C and 5 C, respectively. It is also found that although the hydrothermal treatment has a slight negative effect on the tap-density, it can improve the crystallinity of alpha-Ni(OH)(2) and promote the anion exchange of NO3- by OH-, resulting in a much better electrochemical performance. (C) 2014 Elsevier B.V. All rights reserved.