A battery reacts two different kinds of metal to convert stored chemical energy into electricity through a series of ionic reactions. Batteries produce a strong, consistent current of electricity, ideal for powering electronic devices in a closed electrical circuit.
But how do these metals generate energy? Like Volta’s first model, today’s batteries are composed of three essential parts. Every battery contains two different metals that act as electrodes; depending on their roles in the electrochemical reaction, one metal is called the cathode, and the other, the anode. These two electrode metals are separated by an electrolyte, an intermediary, electricity-conducting substance. In wet cell batteries, the electrolyte is a liquid, like the sulfuric acid solution found in car batteries; in dry cell batteries, the electrolyte is a paste, like in standard AA batteries.
When a battery is connected in a circuit, a series of transformations begins. First, two or more ions – electrically charged molecules – from the anode and the electrolyte combine, causing an oxidation reaction in the anode that releases electrons – negatively charged parcels of energy. These electrons flow out of the battery’s negative end and into the circuit, powering the light, appliance, or electronic device the battery is connected to.
After passing through the device, the electricity flows back towards the battery’s positive end. There, the cathode combines with ions from the electrolyte, causing a reduction reaction and absorbing the electrons. With each oxidation and reduction, the anode and cathode slowly transform from their initial states into different molecules. When a disposable (or primary) battery completely reacts its electrodes, it stops working. But what about rechargeable (or secondary) batteries? Rechargeable batteries use metals like lithium, lead or nickel as electrodes. When these metals are completely used up, they can revert back to their original form by simply running the reaction in reverse.
Considering you’re on a computer right now, it might be hard for you to imagine life without batteries. Although Volta is the official inventor of these marvelous energy packets, the battery may have been in humanity’s bag of tricks for far longer. In the 1930’s, German archeologists unearthed some unusual artifacts just outside of Baghdad, Iraq. What first seemed like simple terracotta pots were found to house copper sheeting wrapped around an iron rod. On further analysis, the pots themselves held acidic residue, perhaps from vinegar or lemon juice. Hopefully, you recognize the three components of a battery. These ancient energy supplies date back to 200 BCE, and have been dubbed the Baghdad batteries.