Batteries

Electrodes

The anode and cathode are the two poles of a battery. They’re important because without them there wouldn’t be a flow of electricity. Anodes and cathodes are usually metals or some other material that conducts electricity well. For example, lead plates work great as anodes in batteries. Zinc works well as a cathode.

Electrolyte

The battery itself is a collection of metal plates separated by an insulator. These plates are called electrodes because they act like little “plates” that collect electrons and send them into the chemical reaction. Electrodes are usually made out of copper, nickel, aluminum, zinc or lead. An electrolyte is what makes the whole thing work. It’s a fluid that allows the passage of positively charged ions. This is important because without an electrolyte, there wouldn’t be enough conductivity to move electrons around. Without an electrolyte, you’d end up with a dead battery. We use an electrolyte to make sure that the electrons don’t simply run off into space. If they did, the battery would lose its ability to store energy. So the electrolyte keeps everything together.

Chemical reactions

The chemical reaction that happens inside batteries is called oxidation–reduction. Oxidation involves taking something apart and reducing it to simpler components. Reducing things usually makes them smaller and lighter. Reduction usually takes place in the presence of oxygen. Oxidizing agents are chemicals that cause the opposite process: breaking down substances and making them bigger. In the case of a battery, oxidizers are chemicals such as potassium hydroxide that react with metals like zinc to form compounds like zinc oxide. These oxides are what we call cathodes. Reducers are chemicals that act like catalysts, speeding up the reduction process. They are often used because they don’t react with the metal being broken down. An example reducer is sulfuric acid. Sulfuric acid reacts with hydrogen gas to produce water vapor. Water vapor doesn’t do much except evaporate. But when it does, it carries away the hydrogen atoms that would otherwise go to break down the metal. This leaves behind the metal compound — the oxide — plus some free protons, which combine with the electrons coming off the metal to form positively charged particles called cations. When the electrons reach the positive electrode, they are captured by the carbon molecules there, forming negatively charged particles called anions. So far, everything looks pretty normal. But now we come to where the magic happens. If the battery is fully charged, the anions and cations are balanced out, and no charge flows. However, if the battery isn’t completely full, some of the anions end up flowing into the electrolyte. As long as there are enough anions left in the electrolyte, the battery will work fine. But once the anions run out, the battery stops working. This is why most modern batteries use a separator to keep the anions from mixing with the cations. Separators are porous materials that let the anions pass through but prevent the cations from getting mixed together. If you’ve ever seen a car battery, you know how important a good seal is to keeping the anions from leaking out. A battery’s casing is designed to keep air out, but a separator prevents the anions from escaping.