Batteries

Your phone, the remote control, the e-bike, your wireless headphones: they all contain stored energy that turns into electricity at the press of a button. A battery is nothing but a tiny chemistry lab in a can. Once you understand what happens inside, you also know why batteries run out and why they never belong in household waste.

Two electrodes, one liquid, one current

A battery needs three things: two electrodes made of different materials and, between them, a conductive liquid or paste called the electrolyte. The two electrodes differ in how readily they give up electrons. Connect them on the outside with a wire and electrons flow from one to the other: that is the electric current. Inside the battery, a chemical reaction runs and supplies those electrons. So batteries convert chemical energy into electrical energy. In the simplest case the electrodes are two different metals: a lemon with a piece of zinc and a piece of copper already becomes a mini battery. In an AA battery from the shop, by contrast, one of the two electrodes is not a pure metal but a metal oxide.

Why does the battery run out?

The chemical reaction in the battery uses up its starting materials. Once they are gone, no more electrons flow: the battery is empty. For a single-use battery, that is the end. A rechargeable battery is built more cleverly: its reaction can be reversed. While charging, the charger pushes the electrons back and restores the starting materials, and afterwards the battery can deliver current again. Phones and electric cars use lithium-ion batteries: they store a lot of energy at low weight and survive many hundreds of charge cycles, but they still weaken over the years.

Valuable and not harmless

Old batteries contain valuable raw materials such as lithium, cobalt, nickel and zinc, which recycling can recover. At the same time, damaged lithium batteries can start fires in the bin or in the rubbish truck. Both point to the same rule: batteries belong in the collection box at the supermarket or at the recycling centre, never in household waste.