The application of Co-Al-hydrotalcite as a novel additive of positive material for nickel-metal hydride secondary cells

Co-Al-CO3 layered double hydroxide (LDH) with the different Co/AI molar ration is synthesized by hydrothermal method and investigated as an additive for positive material of the Ni-MH cells. The Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) show the Co-Al-LDH with Co/Al = 4:1 (molar ration) is well-crystallized and hexagon structure. The electrochemical performances of the nickel electrode added with different Co/Al molar ration Co -Al-LDH, the pure nickel electrode and the nickel electrode added with CoO are investigated by the ;cyclic voltammograms (CV), galvanostatic charge-discharge measurements, and AC electrochemical impedance spectroscopy (EIS). Compared with the pure nickel electrode and the nickel electrode added with CoO, the nickel electrode added with Co/AI = 4:1 (molar ration) Co-Al-LDH has higher discharge capacity and more stable cycling performances. This cell can undergo at least 400 charge discharge cycles at constant current of 1 C. The discharge capacity of this cell remains about 287 mAh g(-1) after the 400th cycle. Meanwhile, compared with the pure electrode, the nickel electrode added with Co/Al=4:1 (molar ration) Co-Al-LDH possess a higher rate capability to meet the needs of high-storage applications. (C) 2014 Elsevier B.V. All rights reserved.