Production of batteries

Ugh, the battery in the remote control died again! I know how to make a battery out of a lemon! I just put a nail and a copper coin into the lemon, connect them by a wire, and… tadaaa! I can prove it to you by connecting this diode. See, it lights up!

Mhmm, nice, but it doesn’t solve my problem. How are you going to stick that into the remote control, huh? You’re right… I wonder how regular batteries are made… Let's look at Leon's lemon setup to see how it works as a battery. The nail made of zinc is the negative electrode of the battery — the anode. The copper coin is the positive electrode — the cathode.

The acidic lemon juice inside the fruit acts as the electrolyte. When the zinc anode and copper cathode are connected by a wire and inserted into the lemon juice electrolyte, a chemical reaction takes place. This reaction causes electrons from the anode to move to the cathode. This creates enough electric current to power, say, a little diode. Most common batteries consist of the same elements: an anode, a cathode, and an electrolyte — set up in a similar way.

But they obviously don’t involve fresh fruit! Most batteries we use in everyday life need to be easily transportable. They also need to fit into and power devices, from remote controls to bike lights and cameras… So, how are these batteries made? The process usually starts with a steel sheet, shaped into cylindrical cases. Meanwhile, in another part of the factory, the cathode of the battery is being made.

It usually consists primarily of two chemical substances: manganese dioxide and graphite. Large batches of these chemicals are mixed together with an electrolyte. This mixture is then pressed to form tiny rings — preforms. These preforms are then stacked on top of each other inside the battery's steel case — making up the cathode. In the next stage, the inside of the preform rings is lined with a separator.

The separator is usually made from layered paper or other porous material, soaked in electrolyte solution. The separator ensures that the cathode and the anode do not come into contact with one another. If they did, the battery would not work! With the separator in place, the anode can be placed inside the battery. The anode is mostly made using zinc.

Zinc powder is mixed with an electrolyte to create a thick paste — zinc gel. The gel is then poured into the hollow of the battery, which is lined with the separator. Now, the battery is ready to be sealed. A plastic seal is inserted into the battery, leaving a space above the gel for expansion and gases created during the chemical reaction. Once the seal is in place, a long brass spike — a nail — is inserted through the seal, into the middle of the battery, where the zinc gel is.

The nail is often called the “current collector.” It gathers the electrons from the anode. Once the battery is placed in a device, the nail directs electrons through the circuit into the cathode. The battery is almost ready! All it needs now is steel plates on the top and bottom. A label containing information about its type, size, manufacturer.

And the “plus” and “minus” markings! The last step is quality control, to ensure the battery works as it should. Once it passes the test, the battery can be packaged, shipped to the store, and used to power your electronics, including the TV remote!