The Charge and Discharge Properties and the Optimum Formulation of a Positive Electrode of Nickel Metal Hydride Batteries

Two layered double hydroxides, [Ni4Al(OH)10]OH and [Co4Al(OH)10]NO3, were synthesized by chemical co-precipitation. The former was used as the active material and the latter as well as graphite were used as the conductive additives, respectively. The optimum ratio of the three materials in a positive electrode was estimated through the simplex-centroid design to improve the charge/discharge properties efficiently at a high current density. When the mass fractions of [Ni4Al(OH)10]OH, [Co4Al(OH)10]NO3 and graphite are 64.45%, 12.27% and 23.28%, respectively, the discharge capacity can retain 270.5 mA·h/g(88.7% of the maximum) after 200 cycles a current density of 800 mA/g.