In the previous chapter, we learned what a battery is and how it supplies electrical energy to a circuit. But have you ever wondered what actually happens inside a battery that allows it to produce electricity?
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In this article, we’ll explore the basic chemistry behind batteries, learn about the three essential parts of every battery, and even see how a simple lemon can be used to generate electricity.
A brief history of the battery
The word “battery” was first used by Benjamin Franklin in 1749.
Interestingly, Franklin wasn’t referring to the batteries we use today. He used the word to describe a group of similar objects connected together—in his case, several Leyden jars, which were early devices capable of storing electrical charge. The word battery simply meant “a collection of similar units working together.”
The first true electric battery was invented in 1800 by the Italian physicist Alessandro Volta.
Known as the Voltaic Pile, it consisted of alternating discs of zinc and copper separated by cloth soaked in saltwater. It was the first device capable of producing a continuous flow of electric current.
Although it could power a circuit for only a relatively short time compared to modern batteries, it laid the foundation for every battery we use today.
Can a lemon produce electricity?
Surprisingly, yes.
A lemon can be used to make a simple battery.
To build one, insert a zinc nail and a piece of copper wire (or a copper coin) into a lemon so that they do not touch each other. Connect several lemons in series and attach an LED across the two ends.
The LED may glow faintly, showing that the lemons are producing electrical energy.
Although a lemon battery cannot deliver much power, it demonstrates the same basic principles used in ordinary batteries.
The three main parts of a battery
Regardless of its size or chemistry, every battery consists of three essential parts:
- Anode – The negative electrode during battery discharge.
- Cathode – The positive electrode during battery discharge.
- Electrolyte – A chemical medium that allows ions to move between the electrodes.
The anode and cathode are made from different materials, while the electrolyte may be a liquid, gel, paste, or solid depending on the type of battery.
In the lemon battery, the zinc nail acts as the anode, the copper wire acts as the cathode, and the lemon juice serves as the electrolyte.
How does a battery generate electricity?
When a battery is connected to an external circuit, chemical reactions begin inside it. At the anode, a reaction called oxidation releases electrons. These electrons cannot travel through the electrolyte, so they flow through the external circuit instead.
As the electrons move through the circuit, they can power devices such as LEDs, motors, or microcontrollers before reaching the cathode.
At the cathode, another reaction called reduction takes place, where the electrons are consumed. As long as these chemical reactions continue, the battery keeps supplying electrical energy to the circuit.
Why don’t electrons travel through the electrolyte?
A common question is why electrons don’t simply travel directly through the electrolyte instead of flowing through the external circuit. The answer is that the electrolyte is designed to conduct ions, not electrons.
Since electrons cannot easily move through the electrolyte, they are forced to travel through the external circuit, where they do useful work before returning to the battery.
This is what allows a battery to power electrical devices.
Why do batteries eventually die?
Every battery contains a limited amount of chemical energy. As the battery supplies current, the chemicals inside it are gradually consumed and converted into new chemical compounds.
Over time, these chemical reactions become weaker, reducing the battery’s ability to produce electrical energy. As a result, the battery voltage gradually decreases until it can no longer power the connected device.
This is why batteries eventually become discharged.
Do all batteries work the same way?
Different batteries use different chemical materials.
For example, alkaline batteries, lithium-ion batteries, lead-acid batteries, and nickel-metal hydride batteries all rely on different chemical reactions.
However, the basic principle remains the same.
Every battery contains two electrodes separated by an electrolyte. Chemical reactions release electrons at the anode, the electrons travel through the external circuit to power a device, and finally reach the cathode, where another chemical reaction takes place.
Types of batteries
Based on whether they can be recharged, batteries are broadly classified into two categories:
- Primary batteries (Non-rechargeable) – Designed for one-time use. Once discharged, they cannot be recharged.
- Secondary batteries (Rechargeable) – Can be recharged and used multiple times by reversing the chemical reactions inside the battery.
We’ll explore both of these battery types in the next chapter.
Summary
A battery generates electricity through chemical reactions taking place between two electrodes separated by an electrolyte. These reactions release electrons at the anode, forcing them to flow through the external circuit before reaching the cathode. This flow of electrons is what powers electronic devices.
Although batteries come in many different shapes and chemistries, they all operate on the same basic principle. Understanding this principle makes it much easier to understand how different battery technologies work and why rechargeable and non-rechargeable batteries behave differently.