What Are the Chemical Reactions That Make Batteries Work?

Batteries are a big part of our everyday life. They power things like smartphones and electric cars. So, how do they work? Batteries use chemical reactions to change stored chemical energy into electrical energy. The main type of reaction in batteries is called oxidation-reduction (or redox) reactions.

1. Oxidation-Reduction Reactions

In a typical battery, there are two parts called electrodes: an anode and a cathode. These parts are soaked in a solution called an electrolyte. When the battery is working, oxidation happens at the anode, and reduction happens at the cathode.

• Oxidation Reaction: At the anode, a substance loses electrons. You can think of it like this:

  $\text{A} \rightarrow \text{A}^{n+} + n \, e^-$

  Here, A shows the substance losing electrons, and ( n ) tells us how many electrons are lost.

• Reduction Reaction: At the same time, a different substance gains electrons at the cathode, shown like this:

  $\text{B}^{n+} + n \, e^- \rightarrow \text{B}$

  In this equation, B is the substance gaining electrons.

These reactions create a flow of electrons from the anode to the cathode through a wire, which produces electricity.

2. Example: Lead-Acid Battery

One common battery type is the lead-acid battery, often used in cars. The chemical changes in lead-acid batteries can be simplified like this:

• At the Anode:

  $\text{Pb} + \text{HSO}_4^- \rightarrow \text{PbSO}_4 + \text{H}^+ + 2 \, e^-$

• At the Cathode:

  $\text{PbO}_2 + \text{HSO}_4^- + 3 \, H^+ + 2 \, e^- \rightarrow \text{PbSO}_4 + 2 \, H_2O$

When we put everything together, it can be summed up like this:

$\text{Pb} + \text{PbO}_2 + 2 \, H_2SO_4 \rightarrow 2 \, \text{PbSO}_4 + 2 \, H_2O$

This shows how lead (Pb) oxidizes and lead dioxide (PbO2) reduces, creating lead sulfate (PbSO4) and water.

3. Energy Output

A lead-acid battery usually works at about 2 volts for each cell. A car battery has six cells, giving it a total of about 12 volts. These batteries can hold energy from around 40 to 80 ampere-hours (Ah). That means they can provide a steady flow of 1 amp for 40 to 80 hours.

4. Real-World Uses

Batteries are very important in many real-world situations:

• Electric Vehicles (EVs): Most electric cars use lithium-ion batteries. These batteries can hold a lot of energy, around 150-250 Wh/kg, which is great for long trips.

• Renewable Energy Storage: Batteries are also key for storing energy from sources like solar and wind power. For example, a lithium-ion battery can store about 18650 mAh at a voltage of 3.7 volts, helpful for home energy systems.

• Consumer Electronics: Devices like laptops and smartphones depend on lithium-ion batteries too. A smartphone battery usually ranges from 3000 to 5000 mAh, allowing it to run for hours.

Conclusion

To sum it up, the chemical reactions in batteries, especially the oxidation-reduction reactions, help change chemical energy into electrical energy. Improvements in battery technology are important for the growth of renewable energy and electric vehicles. This affects our daily lives and the future of our planet. Learning about these reactions helps us understand just how important batteries are to the technology we use every day.