Electrochemical Cells
(Batteries)
SNC1D
Electrochemical Cells
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Cell is another name for battery.
Cells are classified as either primary or
secondary.
In a primary cell, chemical reactions use up
some of the materials in the cell as electrons
flow from it. They can’t be recharged.
When these materials have been used up, the
cell is said to be discharged and cannot be
recharged.*
Primary Cells
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Primary cells can be further classified as either
wet or dry.
The primary wet cell was first developed in
1800 by Italian scientist, Alessandro Volta.
This cell is therefore called the voltaic cell.
Primary Wet Cells
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A wet cell is made up of two pieces of metal
that are placed in a liquid.
The metal plates, usually zinc and copper,
are called electrodes.
The liquid in the cell is called the electrolyte.
An electrolyte is any liquid that conducts an
electric current.
Primary Wet Cells
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Electrons collect at the positive and negative
terminals of the cell.
The cell will only discharge when connected to
a closed circuit.
Primary Dry Cells
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The dry cell is similar to the wet cell, but the
electrolyte is a moist paste instead of a
liquid.
When most of the negative electrode has been
used up by the chemical reaction, the
electrons stop flowing and the cell is
discharged.
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A group of cells make up a battery.
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Simple Primary Wet Cell
 Consists of two different metal electrodes
immersed in
acidic liquid
electrolyte.
 In solution, the
acid molecules
separate into
positive and
negative ions.
Figure 4-1 A simple primary cell
Secondary Cells
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Unlike primary cells, a secondary cell can be
discharged and recharged many hundreds of
times.
Secondary cells are often referred to
rechargeable batteries.
Secondary cells are so named since there are two
chemical processes involved:
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one to discharge the cell
one to charge the cell
A car battery consists of a group of secondary
cells.
Lemon Power
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Battery Arrangements
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Modern Battery Chemicals
Modern batteries use a variety of chemicals to power their reactions. Typical battery
chemistries include:
Zinc-carbon battery - Also known as a standard carbon battery, zinc-carbon chemistry is
used in all inexpensive AA, C and D dry-cell batteries. The electrodes are zinc and carbon,
with an acidic paste between them that serves as the electrolyte.
Alkaline battery - Used in common Duracell and Energizer batteries, the electrodes are
zinc and manganese-oxide, with an alkaline electrolyte.
Lithium photo battery - Lithium, lithium-iodide and lead-iodide are used in cameras
because of their ability to supply power surges.
Lead-acid battery - Used in automobiles, the electrodes are made of lead and lead-oxide
with a strong acidic electrolyte (rechargeable).
Nickel-cadmium battery - The electrodes are nickel-hydroxide and cadmium, with
potassium-hydroxide as the electrolyte (rechargeable).
Nickel-metal hydride battery - This battery is rapidly replacing nickel-cadmium because it
does not suffer from the memory effect that nickel-cadmiums do (rechargeable).
Lithium-ion battery - With a very good power-to-weight ratio, this is often found in high-end
laptop computers and cell phones (rechargeable).
Zinc-air battery - This battery is lightweight and rechargeable.
Zinc-mercury oxide battery - This is often used in hearing-aids.
Silver-zinc battery - This is used in aeronautical applications because the power-to-weight
ratio is good.
Metal-chloride battery - This is used in electric vehicles.
Modern Battery Chemicals
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Battery Cutaway
IfMilliamp-Hour
you arrange four of these
500 milliamp-hour
& 9 1.25-volt,
Volt Cutaway
batteries in a serial arrangement, you get 5 volts (1.25 x 4) at
500 milliamp-hours. If you arrange them in parallel, you get
1.25 volts at 2,000 (500 x 4) milliamp-hours.
Have you ever looked inside a 9-volt battery?
It contains six, very small batteries producing 1.5 volts each in
a serial arrangement!
Battery Cutaway
Battery Cutaway
Figure 7 One of the Cells in a 12-V Lead Storage Battery (LSM 14.1C)
Battery Cutaway
Figure 6 A Common Dry Cell Battery (LSM 14.1C)