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August 2000
NICKEL METAL HYDRIDE HANDBOOK, PAGE
7
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.
NICKEL METAL HYDRIDE 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.