A battery is a portable energy source that is made up of three basic components: an anode, a cathode, and an electrolyte.
The anode is the negative portion, the cathode is the positive portion, and the electrolyte is the liquid solution which conducts ions aiding in the flow of energy. In zinc chloride batteries, the cathode is the inside portion of the battery and the anode is on the outside. In alkaline batteries, the alkaline cathode is on the outside and the alkaline anode is on the inside.
Voltage
The voltage is the force that pushes electricity through a circuit. A battery provides that force in a circuit. The force can be strong or weak, depending on the source. A single cell battery produces a relatively weak force of only 1.5V. A greater voltage, such as one created by linking many such cells together produces a much greater force.
Electron Flow in a Battery
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Electrons flow out of a battery from the negative
end to the positive end. Because electrons
are negatively charged, they are attracted to the positive end
of a battery and repelled by the negative end. When a battery is connected
in a circuit that lets the electrons flow through it, they flow from
negative to positive.
Electrons don't just flow back through the battery until the charge changes enough to make the voltage zero. An electron can't move from one side to the other inside the battery without a chemical reaction occurring. The chemical reaction is what pushes the electrons inside toward the negative end. Electrons flow around the circuit toward the negative end of the battery, pushed by the chemical reaction, and toward the positive end in the outside circuit. |
The one common characteristic for commercial batteries is that they are based on chemical systems with the same principle of operation. These internal reactions are chemically classified as redox, short for reduction-oxidation. That means battery chemistry relies on the reduction and oxidation of molecules--that is, prying oxygen ions off some molecules and gluing them onto others. Oxidation is the same energy-releasing process that makes fire, though in that case the reaction is a bit quicker and often less controlled.
A byproduct of the redox operation is that electrons are freed from molecules in the process, which can produce an electrical current capable of heating a filament in a flashlight bulb or operating the sophisticated electronic circuitry of a computer or other high-tech device.
All commercial batteries work by the same principle. Two dissimilar materials
serving as anode and cathode are linked by a third material that serves as the
electrolyte. The choice of materials for both the electrodes and electrolyte is
wide and allows for a diversity of battery technologies. It also influences the
the amount of energy that can be stored in a given size or weight of battery and
nominal voltage output.
| How a RayoVac Battery is Made
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The alkaline cathode is a mixture of manganese dioxide, graphite and an electrolyte. |
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The mixture is granulated, aged, and then compacted into a pressed tablet assembly. |
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Next, these tablets are inserted into a steel can. The steel can and the mixture become the cathode of the alkaline battery. An indentation is then made near the top of the can and the sealant is placed just above it. These two steps help safeguard the battery against leakage. |
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As with the zinc chloride battery, the cathode and the anode portions of the alkaline battery must be kept from coming into contact with one another. Therefore, we must insert a paper separator, which is soaked with an electrolyte that promotes ionic, or electrolyte, conductivity once the battery is in use. |
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We now insert the anode. In alkaline batteries, the anode is actually a gel made up of mostly zinc powder and several other materials. This gel is inserted into the steel can against the separator paper. |
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With the anode and cathode in place, we now have a usable alkaline
battery. However, because it is unsealed, the battery would not have a
long shelf life. Therefore, a seal must be used to ensue the high
quality and performance of the alkaline battery.
The seal is made up of a brass nail, which acts as the current collector, a plastic gasket, a steel washer and a metal end cap. The four items are pre assembled and inserted into the middle of the steel can, up against the indentation which was formed earlier. |
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A top is welded to the other end of the can to provide the positive
polarity safety feature. The batteries are then stored, given a second voltage test, and a decorative outer label is applied. |
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Baghdad Battery |
A 6-inch high clay pot with a cylinder of sheet copper measuring 5 inches by 1.5 inches on the inside. This was welded by a 60-40 lead-tin alloy to the bitumen (or asphalt) top. The bottom of this cylinder was capped with a crimped in copper disk and was also sealed with bitumen. The rod showed some evidence of having been eroded with an acidic agent, which gave rise to the idea of it being a battery. Testing the device by adding plain old pineapple juice, the most probable acid that could have been used, it was found that the device yielded about 1.5V. In later experiments using vinegar and other weak acids up to about 2V were measured.
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| The carbon rod inside a typical alkaline battery is the positive electrode. The zinc can, in which the components of the battery are encased, is the negative electrode. The chemical reaction occurs in the middle of the battery when the carbon, manganese dioxide, and ammonium chloride combine. |
Dry Cell
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Inside a Nickel Cadmium battery
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Inside a Nickel Hydride rechargeable battery |
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| To avoid injury, manufacturers caution against disassembling batteries. A partially disassembled 9-volt battery would look like this. |
 
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