The Chemistry Of Batteries Essay, Research Paper
The Chemistry Of Batteries
People use batteries in their everyday life without thinking of their
impact. Batteries help us get around, keep in touch, have fun, and tell the
time. They do this by powering our cars, cell phones, pagers, portable CD
players, watches and many other useful tools. They can even save our lives
by powering things like smoke detectors, carbon dioxide detectors and
glucose meters. In this term paper I will discuss how batteries function,
what types of batteries exist, what gives them their power and many other
topics related to batteries.
The battery, also known as an electric cell, is a device that converts
the energy from chemicals into electricity. Chemical reactions that are able
to produce electrons are called Electro-chemical reactions. A battery
basically consists of two or more cells that are connected in a series or
parallel. All cells are made of a liquid, paste, or solid electrolyte and a
positive electrode, as well as a negative electrode. The electrolyte works as
an ionic conductor, this causes one of the electrodes to react. This reaction
produces electrons while the other electrode accepts the electrons. Every
battery has two terminals, one positive and the other negative. Electrons
collect on the negative terminal of the battery. If the negative and positive
terminal are connected together, then connected to whatever device that
needs to be powered, also called a load, the electrical current will flow freely
into the device.
The speed of the electron production by the chemical reaction is called
the battery s internal resistance. This controls how many electrons can flow
between the two terminals. Because electrons must flow from the battery
into a wire, and then must travel from the negative to the positive terminals
in order for the chemical reaction to take place. This is why batteries can go
unused for a year and still have plenty of power.
There are two general types of batteries. Batteries that have chemicals
that cannot be reconstituted into their original form after the energy has been
used are called primary cells or voltaic cells. Batteries that contain
chemicals which can be reconstituted when an electric current is passed
through them in an opposite direction of normal cell operation are called
rechargeable cells, storage cells, secondary cells, or accumulators.
Primary cells or dry cell batteries are the most common type of battery
used today. Primary cells were invented by the French chemist Georges
Leclanche in the late 1860 s. During that period this invention was very
important and helped the start of the industrial revolution. It is commonly
know as a dry cell or flashlight battery. The Leclanche cell is very similar to
the dry cell that is used today. The electrolyte is made of zinc, on the
outside shell of the cell, the positive electrode is made of carbon and is
surrounded by a mixture of carbon and manganese dioxide. zinc-carbon
chemistry is used in all AA, C and D dry cell batteries. When the cell is in
use, atoms of the zinc in the outer cases are oxidized, giving up electrons and
forming zinc ions.
Another type of primary cell is a mercury cell. This cell uses zinc as
the negative electrode, mercuric oxide as the positive electrode and an
electrolyte made of a solution of potassium hydroxide. This cell can be
made in the shape of a very small flat disk and is used in electric
wristwatches, hearing aids, and photoelectric cells.
The lead acid cell, also called commercial secondary or storage cell
was invented in 1859 by French physicist Gaston Plante. As mentioned
before, this cell can be recharged by reversing the chemical reaction.
Plante s original cell was a lead acid battery, which is still widely used
today. Just as with Leclanches s cell, it has been vastly improved on over
time. It consists of a lead negative electrode, a sulfuric acid electrolyte, a
porous polymer or glass separator and a lead dioxide positive electrode. As
the cell is used, lead sulfate forms at both electrodes and the sulfuric acid is
consumed. When it is recharged, the lead and lead oxide are remade and
more sulfuric acid is formed. This secondary cell produces 2V, a number of
these cells are typically combined in series to make up 6 or 12V batteries.
Advances in technology have recently made it possible for lead batteries to
have useful lives of 50 to 70 years. Lead acid batteries are commonly used
in automobiles for starting, lighting, and ignition. Another very important
use is for uninterruptable power supply systems for computer and telephones
systems.
The lead acid battery is known to be the lowest costing of secondary
batteries. When it is used in a way where it is never fully discharged, like
starting an automobile, it can last for up to 20 years and for many recharging
cycles. It has a much shorter lifetime when it is used for other applications,
for example powering a golf cart, when it is greatly discharged. If the
battery is overcharged it will quickly wear out due to internal corrosion and
loss of water. During these times when environmental pollution is such a
problem, over 95 percent of lead acid batteries are recycled into new
batteries.
An improvement on the nickel iron battery that was developed by
inventor Thomas Edison in the 1900 s, is the nickel cadmium battery. The
nickle cadmium battery has a cadmium negative electrode, a potassium
hydroxide electrolyte, a nonwoven fabric separator, and a nickel positive
electrode. It produces 12V and endures many more full discharges cycles
than the lead acid battery ( up to 1000). It s a small cell that is commonly
used in portable tools like telephone, electric toothbrushes and shavers.
Interestingly enough it is also used in air planes where long life is truly
important.
An improvement of the nickle-cadmium cell is the nickel metal
hydride cell, the cadmium negative electrode is replaced with a complex
metal alloy that, absorbs hydrogen gas as it is charged and sends it to the
electrolyte as it discharges. This solves the problem of the hydrogen
potentially causing an explosion. The nickel metal hydride cell has 50
percent more power then the nickel cadmium cell. It has mostly replaced the
nickel cadmium cells in notebook computers and cellular phones
Batteries are a vital tool to our everyday lives. With technology
rapidly expanding by the day, researchers in battery technology are
continually exploring different ways to make batteries. There is now more
then ever, an expanding array of technologies that need batteries to power
them. There are numerous types of batteries that have been developed for
electric cars and more powerful portable devices. Size, short range,
environmental issues and high expense are all problems to be solved for
these new endeavors. Cutting edge batteries that show promise for electric
vehicles are sodium sulfur, lithium ion sulfide, zinc chlorine, and nickel
metal hydride all seem to show promise. Solar batteries are another kind of
cell technology. They produce electricity by a photoelectric conversion
process. Electricity is made from a photo sensitive semiconducting
substance like silicon crystal. It s functions by light hitting the crystal
causing electrons to be dislodged from the surface of the crystal. These
electrons then move to an opposite surface. They are then collected as a
currant of electricity. Solar batteries have the advantages of long lifetimes.
They are used in space to provide electricity for operation of equipment
abord spacecraft s.
Research is currently being done on the possible use of organic
polymers and solid inorganic conductors as electrolytes. New materials for
the use of both positive and negative electrodes is also being researched.
Batteries play a very important role in our everyday lives. Many different
devices we have come to reply upon require batteries to supply them with
the power they need. Advancement in battery technology are working to
reduce environmental hazards caused by batteries and to make them more
compact.
The battery is a true universal source of energy that is used around the
world. Learning about how batteries function and about the many different
types of batteries has helped me to appreciate them a lot more. Batteries are
a valuable source of power that people use everyday but also take for
granted. Batteries will continue improving the quality of our lives.
Bibliography
Battery Funk & Wagnalls New Encyclopedia. 1987, Volume 3, pp.
346-347
Funk and Wagnalls. (on line) Available http://www.funkandwagnalls.com/
May 3, 2000
Marshall, Brian How batteries work (online). Available
http://www.hotstuffworks.com/ April 25, 2000
Microsoft Encarta 97 Encyclopedia. On CD-Rom. 1993-1996 Microsoft
Corporation.