A zinc-air battery is a primary battery that uses activated carbon to adsorb oxygen or pure oxygen from the air as the positive electrode active material, zinc as the negative electrode, and ammonium chloride or caustic alkali solution as the electrolyte.
The charging process of zinc-air batteries is very slow. To solve this problem, when the negative electrode zinc plate or zinc granules of zinc-air batteries are oxidized into zinc oxide and fail, the zinc plate or zinc granules and electrolyte are usually replaced directly to completely renew the zinc-air battery.
There are four main types.
① Neutral zinc-air battery: The structure is similar to that of the zinc-manganese cylindrical battery. It also uses ammonium chloride and zinc chloride as electrolytes. The only difference is that activated carbon is used instead of manganese dioxide in the carbon bag, and ventilation holes are left on or around the cover, which are opened when in use;
② Button-type zinc-air battery: The structure is basically the same as that of zinc-silver button battery, but there is a small hole on the positive electrode casing, which can be opened for use;
③ Low-power, high-capacity zinc-air wet cell: An electrode assembly consisting of sintered or bonded activated carbon electrodes and plate-shaped zinc electrodes is immersed in a container filled with sodium hydroxide solution;
④ High-power zinc-air batteries: These typically consist of a thin, bonded activated carbon electrode mounted on the outer wall of the battery, with a zinc powder electrode placed in the center. The two are separated by a liquid-absorbing membrane, and a liquid-filling plug is installed at the top. Potassium hydroxide solution is injected during use. These batteries are easy to carry.
Low-power zinc-air wet batteries and high-power zinc-air batteries are temporary activation type. The activated carbon electrode can be reused. Therefore, after the battery is depleted of its charge, it can be reused simply by replacing the zinc electrode and the alkaline solution.
The key to preserving zinc-air batteries lies in the seal; the cathode seal should not be removed unless the battery is ready for immediate use. Simulation tests show that at room temperature, the charge drops to 95% after one year, to 90% after two years, and still retains 85% after four years. Once the seal is removed, the battery is activated and begins to function. At room temperature without a load, depending on the battery size, the charge drops by 50% after 3 to 12 weeks, and to 0-10% after more than 20 weeks.
Zinc-air batteries are suitable for applications where the battery is to be depleted within a few weeks. If the seal on a zinc-air battery is torn off, air enters and activates the electrochemical reaction inside. Even if the seal is reapplied, the electrochemical reaction will continue until the battery is depleted.
Large zinc-air batteries typically have a charge capacity of 500–2000 Ah and are mainly used in railway and marine beacon devices. Button-shaped zinc-air batteries have a charge capacity of 200–400 mAh and are widely used in hearing aids.
