NICKEL METAL HYDRIDE BATTERIES
Overview
As electronic products have come to feature more sophisticated functions, more compact sizes and lighter weights, the sources of power that operate these products have been required to deliver in- creasingly higher levels of energy. To meet this requirement, nickel-metal hydride batteries have been developed and manufactured with nickel hydro- xide for the positive electrode and hydrogen-absorb- ing alloys, capable of absorbing and releasing hydro- gen at high-density levels, for the negative electrode. Because Ni-MH batteries have about twice the energy density of Ni-Cd batteries and a similar operating voltage as that of Ni-Cd batteries, they are expected to become a mainstay in the next genera- tion of rechargeable batteries.
Construction
Nickel-metal hydride batteries consist of a positive plate containing nickel hydroxide as its principal active material, a negative plate mainly composed of hydro- gen-absorbing alloys, a separator made of fine fibers, an alkaline electrolyte, a metal case and a sealing plate provided with a self-resealing safety vent. Their basic structure is identical to that of Ni-Cd batteries. With cylindrical nickel-metal hydride batteries, the positive and negative plates are seperated by the separator, wound into a coil, inserted into the case, and sealed by the sealing plate through an electrically insulated gasket.
With prismatic nickel-metal hydride batteries, the positive and negative plates are sandwiched together in layers with separators between them, inserted into the case, and sealed by the sealing plate.
NICKEL METAL HYDRIDE HANDBOOK, PAGE 7 | August 2000 |
