A new battery, made only of solid materials charges into the market
AN AMERICAN company, Ultralife
Batteries, has launched the world's first
lightweight rechargeable battery made
entirely from solid materials. The battery, launched a few weeks ago, can be
recharged more than 1,000 times with
only a tiny loss of capacity. In comparison, conventional batteries can be
recharged a maximum of 200 times
(New Scientist, Vol 146, No 197 1).
Being completely solid, Ultralife
batteries can be shaped to suit any size
to power portable equipment such as
laptop computers, camcorders and
mobile telephones, or if current
research efforts succeed, even automobiles, according to Colin Newnham, the
vice-president of rechargeable product
development at Ultralife. The batteries
can be made thinner than a millimetre
and with as large an area as that of an
A4 sheet of paper.
Unlike conventional nickel-cadmium, rechargeable batteries, which contain liquid electrolytes, Ultralife batteries contain lightweight lithium-based
electrodes and a solid polymer electrolyte - whose exact composition is a
closely guarded secret. As it is entirely
solid, there is no danger of any chemicals leaking out. The manufacturer
says that the safety factor of the batteries
on this account gives them an edge
over Japanese companies, including
Sony, Sanyo and Matsushita, which
have launched rechargeable lithium
ion-based batteries, but with liquid
electrolytes.
The new battery is known as "rocking chair" or "shuttle -cock" cell,
because it relies on lithium ions passing
to and fro as it is charged and discharged. While discharging, lithium
ions migrate from the flat carbon anode,
cross a layer of polymer electrolyte and
combine with the cathode material on the other
side to form lithiated
manganese oxide. Sheets
of metallic mesh on the
top and the bottom of the
cell act as current collectors. Recharging reverses
this process. The cell is
sealed in laminated aluminium foil to keep the
moisture out.
Ultralife will soon be
supplying an unnamed
multinational communications company with the
first commercial version
of the battery, for use in
,d mobile phones. Newnham says that the new
batteries would cost around us $1 per
watt-hour - the same price as energy
from nickel-cadmium rechargeable batteries. He expects the product to undercut other lithium-based rechargeable
batteries as it uses cheaper lithiated
manganese oxide cathode material.
The motor industry has taken a keen
interest in lithium battery technology
for possible use in electric cars.
American car manufacturers Ford,
General Motors and Chrysler are collaborating with the us government in their
own us $1.5 billion lithium battery
development programmes.
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