The terms "straight" and "reverse" polarity are used around the shop. They may also be expressed as "electrode-negative" and "electrode-positive" polarity.

Each cell consists of a negative electrode and a positive electrode kept apart by a separator soaked in a conductive electrolyte that allows ions, but not electrons, to travel between them.

The batteries commonly used in today's mobile phones and laptops still use cobalt oxide as the positive electrode.