What’s inside a battery?
A battery, like everything else, is made up of atoms. An atom is composed of three types of particles:
- protons (positive)
- electrons (negative)
Ideally, the charge is balanced, with an equal number of negative and positive particles. When one electron (a negative particle) is removed from an atom, it becomes positive, and vice versa. Because atoms desire to remain neutral, they will seek out other atoms to trade electrons with in order to restore their equilibrium. The 'flow' of electrons forms an electrical current.
The chemistry of and anode, electrolyte and cathode
In batteries, the process of swapping electrons also takes place. Every battery has three components: an anode, an electrolyte, and a cathode. However, different battery types use different chemicals to make these pieces.
In a fully charged battery, the anode is negatively charged and the cathode is positively charged. Why? The anode has a surplus of (negative) electrons, whereas the cathode has none. Presumably, the anode would like to lose some of its electrons by passing them to the cathode.
You can control the flow and build a battery by adding a third piece, the separator with electrolyte. The separator functions as a barrier between the anode and cathode inside the cell. When the battery is linked to a gadget, it only permits an electric current to flow.
How do rechargeable batteries work?
This is how all batteries work: electrons go from an anode to a cathode until the anode runs out of electrons. As a result, the battery is considered 'dead' or empty.
That's the end of it with primary batteries. A charger can reverse the electron flow in secondary or rechargeable batteries, restoring the initial excess of electrons in the anode and thus establishing what we call a charged battery.
All batteries work this way: electrons travel from an anode to a cathode until the anode is out of electrons.
The ability to reverse this reaction is dependent on the chemicals utilised in the battery. Alkaline batteries, for example, are not designed to support reverse flow. This has the potential to be dangerous.
A NiMH (Nickel-Metal Hybrid) battery can be made to reverse flow hundreds, if not thousands, of times. The process, however, causes chemical damage over time. As a result, batteries cannot be infinitely recharged and depleted: at some time, the chemicals will have decayed too much to continue storing a charge.
How do rechargeable batteries work time after time, then? How great the lifespan of a re-chargeable battery is depends on the manufacturer, the type of battery and the conditions in which it is used.