The demand for many varieties of rechargeable batteries is due to their
lower cost and lower environmental impact.
LEARNING OBJECTIVE [ edit ]
Discuss the general characteristics of rechargeable batteries
KEY POINTS [ edit ]
Rechargeable batteries store energy through a reversiblechemical reaction, which allows charge to
be stored again after the battery has been drained.
Rechargeable batteries have lower total cost of use and environmental impact than disposable
batteries, which might be why the U.S. demand for rechargeable batteries is growing much faster
than is the demand for non-rechargeable batteries.
Common types of rechargeable batteries are lead-acid, nickel-cadmium (NiCd), nickelmetal hydride (NiMH), lithium-ion (Li-ion), lithium-ion polymer (LiPo), and
rechargeable alkalinebatteries.
TERMS [ edit ]
energy density
The amount of energy that can be stored relative to the volume of the battery.
secondary cell
An electric cell that is rechargeable because it converts chemical energy into electrical energy by a
reversible chemical reaction.
Give us feedback on this content: FULL TEXT [edit ]
Rechargeable Batteries
A rechargeable battery is a type of electrical battery that is comprised of one or
more electrochemical cells. It is known as asecondary cell because its electrochemical
reactions are electrically reversible. In
other words, after the stored charge has
been drained, the battery's chemical
reactions can occur again, in reverse, to
store a new charge. The U.S. demand for
rechargeable batteries is growing twice as
fast as the demand for non-rechargeable
batteries, in part because rechargeable
batteries have lower environmental impact
and total cost of use than do disposable
Register for FREE to stop seeing ads
batteries.
Grid energy storage applications use rechargeable batteries for load-leveling. Load-leveling
involves storing electric energy for use during peak load period. By charging batteries during
periods of low electrical demand for use during periods of high demand, load-leveling helps
eliminate the need for expensive peaking power plants and helps reduce the cost of
generators over more hours of operation.
Rechargeable Battery Construction
As with all batteries, rechargeable batteries consist of an anode, a cathode, and an electrolyte.
During charging, the anode material is oxidized, producing electrons, and the cathode is
reduced, consuming electrons.
Current
Charge
Charger
Positive
Negative
Separator
Cathode
Charging a battery
Electrolyte
Anode
Diagram of charging a battery.
These electrons constitute the current flow in the external circuit. The electrolyte may serve
as a simple buffer for internal ion flow between the electrodes, as in lithium-ion and nickelcadmium cells, or it may be an active participant in the electrochemical reaction, as in leadacid cells.
Types of Rechargeable Batteries
Several different combinations of chemicals are commonly used in rechargeable batteries.
Different types include lead-acid, nickel-cadmium (NiCd), nickel-metal hydride (NiMH),
lithium-ion (Li-ion), lithium-ion polymer (LiPo), and rechargeable alkaline batteries.
Lead-Acid Batteries
Lead-acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of
rechargeable battery. Their ability to supply high-surge currents means that the cells
maintain a relatively large power-to-weight ratio. These features, along with their low cost,
make them attractive for use in motor vehicles, which require high currents.
Nickel-Metal Hydride Batteries
A nickel-metal hydride battery, abbreviated NiMH or Ni-MH, is very similar to the nickelcadmium cell (NiCd). NiMH batteries use positive electrodes of nickel oxyhydroxide
(NiOOH), as does the NiCd, but the negative electrodes use a hydrogenabsorbingalloy instead of cadmium. A NiMH battery can have two to three times the capacity
of a NiCd battery of equivalent size, and its energy density approaches that of a lithium-ion
cell.
Lithium-Ion Batteries
The lithium-ion battery is a family of rechargeable batteries in which lithium ions move from
the negative electrode to the positive electrode during discharge, and back when charging.
The negative electrode of a conventional lithium-ion cell is made from carbon. The positive
electrode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent. They are
one of the most popular types of rechargeable battery for portable electronics, with one of the
best energy densities and only a slow loss of charge when not in use. Lithium ion batteries are
more expensive than NiCd batteries but operate over a widertemperature range while being
smaller and lighter. They are fragile and thus need a protective circuit to limit peak voltages.
Lithium-Ion Polymer Batteries
Lithium-ion polymer (LiPo) batteries are usually composed of several identical secondary
cells in parallel to increase the discharge-current capability. They are often available in series
"packs" to increase the total available voltage. Their primary distinction from lithium-ion
batteries is that their lithium salt electrolyte is not held in an organic solvent. Instead, it is in
asolid polymer composite, such as polyethylene oxide or polyacrylonitrile. The advantages of
LiPo over the lithium-ion design include potentially lower cost of manufacture, adaptability
to a wide variety of packaging shapes, reliability, and ruggedness. Their major disadvantage is
that they hold less charge.
Alkaline Batteries
There are also rechargeable forms of alkaline batteries, which are a type of primary battery
dependent upon the reaction between zinc (Zn) and manganese dioxide (MnO2). They are
manufactured fully charged and have the ability to carry their charge for years, longer than
most NiCd and NiMH batteries, which self-discharge. Rechargeable alkaline batteries can
also have a high recharging efficiency and have less environmental impact than disposable
cells.