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Q & A: Chemical Batteries

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Most recent answer: 10/22/2007
Q:
I would like to know how a battery works, and why it works in that way?
- sissela
Helsingborg, Skania, Sweden
A:

Most batteries have two electrodes made of different materials, with some sort of chemical solution or paste in between. When the battery is used, chemicals near each of the electrodes do different chemical reactions. One reaction deposits electrons on one electorde and the other reaction pulls electrons off the other electrode. The electrons flow through a circuit from the electrode where they're being deposited to the electrode from which they are being pulled. (Flowing electrons are called current.)  On the way through the circuit the current drives a radio or whatever device the battery is running.

The chemical reactions at the two electrodes always have to be different. Otherwise, there would be no reason for the electrons to push from one side to the other.  The chemicals have to start in a high energy (more precisely, high free energy) state, so that in falling down to the lower energy state they can supply energy to the circuit. As the battery is used, the chemicals inside are used up, leaving some lower-energy forms. Eventually, the high-energy forms get used up and the battery is "dead".

Different types of batteries use different chemicals. Car batteries use lead at one electrode and lead oxide at the other with sulfuric acid in between. (https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery) Cell phones and laptop computers used to use nickel-cadmium batteries (https://en.wikipedia.org/wiki/Nickel%E2%80%93cadmium_battery). Now they more often use lithium ion batteries, with electrodes made of graphite and cobalt oxide and the lithium shuttling in between. (https://en.wikipedia.org/wiki/Lithium-ion_battery) The standard alkaline batteries you see in a store use zinc and manganese dioxide electrodes with an alkaline solution in between.(https://en.wikipedia.org/wiki/Alkaline_battery)

Adam (& Mike W.)


(published on 10/22/2007)

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