Components of Cells and Batteries
Cells are comprised of 3 essential components.
The Anode is the negative or reducing electrode that releases electrons to the external circuit and oxidizes during and electrochemical reaction.
The Cathode is the positive or oxidizing electrode that acquires electrons from the external circuit and is reduced during the electrochemical reaction.
The Electrolyte is the medium that provides the ion transport mechanism between the cathode and anode of a cell. Electrolytes are often thought of as liquids, such as water or other solvents, with dissolved salts, acids, or alkalis that are required for ionic conduction. It should however be noted that many batteries including the conventional (AA/AAA/D) batteries contain solid electrolytes that act as ionic conductors at room temperature.
Considerations in selection of Cathode, Anode and Electrolyte
Desirable properties for anode, cathode, and electrolyte materials are noted below.
Anode material should exhibit the following properties
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Efficient reducing agent
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High coulombic output
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Good conductivity
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Ease of fabrication
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Low cost
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Metals such as Zinc and Lithium are often used as anode materials.
Cathode material should exhibit the following properties
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Efficient oxidizing agent.
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Stable when in contact with electrolyte
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Useful working voltage
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Ease of fabrication
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Low cost
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Metallic oxides such as are often used as cathode materials
The most desirable anode-cathode material combinations are those that result in light-weight cells with high voltage and capacity. Such combinations may not always be practical as a result of extenuating factors such as material handling difficulty, reactivity with other cell components, difficulty of fabrication, polarization tendencies, and cost prohibitive materials.
Electrolytes should exhibit the following properties
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Strong ionic conductivity
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No electric conductivity
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Non-reactivity with electrode materials
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Properties resistance to temperature fluctuations
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Safeness in handling
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Low cost
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Aqueous solutions such as dissolved salts, acids, and alkalis are often used as electrolytes
