| Layered double hydroxides (short as LDHs) are composed of rigid hydroxide layers, interlamellar anions and co-crystallized water. They outstand there because of their marvelous reversible anion-exchange capabilities and have been found uses in anion exchange, preparations of various materials, chemical separations of organic geometric isomers, controls of chemical reactions, storage and control release of biomolecules, preparation of flame retarding materials/addictives, catalysts and catalysts supports and topochemical syntheses in the recent years. They can also be employed as electrode materials. In this paper, electrochemical performances, especially the electrochemical reversibilities and charge-discharge capacities at high currents, of layered double hydroxides with a ideal composition of [Ni4Al(OH)10]X?mH2O (X = OH-, NO3-)are investigated.In the second chapter of this paper, cyclic voltammetry, X-ray diffraction, X-ray photoelectron spectrum, inductively coupled plasma are employed to investigate electrochemical behaviours of a layered double hydroxide, [Ni4Al(OH)10]OH, as well as any changes of its crystal structure and valance transformation of nickel ions during charge-discharge cycles. The results show that the layered structure of [Ni4Al(OH)10]OH is stable to charge-discharge cycles; and the valence transformation of nickel ions in the hydroxide layer is confirmed by XPS. The discharge capacities of the electrode are found to be 248 mAh?g-1 at the first cycle, a maximum of 330 mAh?g-1 are found at the 25th cycle, and 315 mAh?g-1 at the 60th cycle.The electrochemical performances of a layered double hydroxide, [Ni4Al(OH)10]NO3 of different particle sizes are reported. The results show that the particle size of the sample has evident effect on its discharge capacity at high current densities: sample of bigger particle size may have a larger capacity when they are discharged at lower current density; but their capacity decreases quickly when the current density is increased; however, the capacity of samples of smaller particle size remains high even at very high current density, i.e. 4000 mA?g-1.Electrochemical comparisons of [Ni4Al(OH)10]OH and [Ni4Al(OH)10]NO3 were done in the last chapter of this paper, which show that the former has better performance, especially when the discharge is carried out at very high current densities. For example, the discharge capacity of the former, which is 348.8 mAh?g-1 (corresponding to 1.78 electrons exchanged per nickel atom), is higher than that of the latter, which is 332.9 mAh?g-1 (1.66 electrons exchanged per nickel atom) at a current density of 50 mA?g-1; the former also has a capacity of 195 mAh?g-1 at a current density as high as 2500 mA?g-1, which is also larger than that of [Ni4Al(OH)10]NO3, 144.6 mAh?g-1. In addition, studies on the effect of charge current densities on the discharge capacities of the two samples show that each sample has very similar discharge capacity no matter it is charged at 1666 mA?g-1, 833.3 mA?g-1 or 416.7 mA?g-1 when the sample is overcharged and discharged at a current density of 833.3 mA?g-1.
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