Electrochemical Cells (Batteries)

1. Electrochemical Cells (Batteries) SNC1D

2. Electrochemical Cells • Cell is another name for battery. • Cells are classified as either primaryor 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.*

3. Primary Cells • Primary cells can be further classified as either wetor dry. • The primary wet cell was first developed in 1800 by Italian scientist, Alessandro Volta. • This cell is therefore called the voltaic cell.

4. Primary Wet Cells • A wet cell is made up of two pieces of metal that are placed in a liquid. • The metal plates, usually zincand copper, are called electrodes. • The liquid in the cell is called the electrolyte. • An electrolyte is any liquid that conducts an electric current.

5. Primary Wet Cells • Electrons collect at the positive and negative terminals of the cell. • The cell will only discharge when connected to a closed circuit.

6. Primary Dry Cells • 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. • A group of cells make up a battery.

7. Consists of two different metal electrodes immersed in acidic liquid electrolyte. • In solution, the acid molecules separate into positive and negative ions. Simple Primary Wet Cell Figure 4-1 A simple primary cell

8. Secondary Cells • Unlike primary cells, a secondary cellcan 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: • one to discharge the cell • one to charge the cell • A car battery consists of a group of secondary cells.

9. Lemon Power http://electronics.howstuffworks.com/framed.htm?parent=battery.htm&url=http://members.aol.com/dswart/index.html

10. Battery Arrangements http://electronics.howstuffworks.com/battery8.htm

11. Modern Battery Chemicals 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. http://electronics.howstuffworks.com/battery7.htm

12. Milliamp-Hour & 9 Volt Cutaway Battery Cutaway If you arrange four of these 1.25-volt, 500 milliamp-hour 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!

13. Battery Cutaway

14. Battery Cutaway Figure 7 One of the Cells in a 12-V Lead Storage Battery (LSM 14.1C)

15. Battery Cutaway Figure 6 A Common Dry Cell Battery (LSM 14.1C)