An alkaline battery is a type of a dry cell primary battery that employs the chemical reaction of zinc and magnesium oxide and uses an alkaline electrolyte of potassium hydroxide to generate electric current. It is currently the most popular type of disposable battery in the market. Common applications include small electronic devices such as clocks and flashlights, as well as portable radio and electronic toys.
Note that an alkaline battery is a primary battery. It is intended for disposal upon single use. However, manufacturers have come up with specially designed battery cells to produce rechargeable alkaline batteries.
How does alkaline battery work?
Remember that batteries have negative electrode or anode and positive electrode or cathode. In an alkaline battery, the anode is the zinc and the cathode is the magnesium oxide. Modern alkaline batteries also have carbon in the cathode mix. Understanding the chemical reaction of zinc and magnesium oxide is essential to understanding how alkaline battery works.
Chemical reactions transpire in the anode and cathode due to their individual interactions with the ions from the alkaline electrolyte solution of potassium hydroxide.
In the zinc anode, an interaction with ions of potassium hydroxide causes a build up of excess electron. This build up results in an electrical difference between the anode and cathode. Furthermore, because of the build up of electrons in the zinc anode, they would have the natural tendency to move somewhere else. In an alkaline battery, these excess electrons should move in the magnesium oxide cathode. This is impossible by default because there is no direction connection between the anode and the magnesium cathode.
Allowing the excess electrons to move requires creating a closed circuit—particularly by placing the alkaline battery into a device. The movement of the electrons from the anode to the cathode via the closed circuit creates an electric current. This is how alkaline batteries power electronic devices.
It is also important to note that the magnesium oxide cathode able to receive the excess or free electrons due to its interaction with the ions from the alkaline electrolyte solution of potassium hydroxide. To be specific, the reaction ions from the electrolyte reacting with free electrons to form compounds.
Advantages and disadvantages of alkaline battery
One of the advantages of alkaline battery over other primary batteries and rechargeable batteries is that it has higher energy density. For example, this battery has double the energy density of a Leclanché cell and zinc-carbon batteries. This allows the battery to produce the same energy while lasting longer than other batteries.
The rechargeable variant of this battery also has four times the capacity of an equivalent nickel cadmium or nickel metal hydride batteries.
Longevity is another advantage of alkaline battery. It has longer shelf life than batteries with chloride-type electrolyte. It could last to up to seven years unused, losing about five percent of its energy every year. This means that it does not easily run out of power while not in use. This battery also functions even at very low temperatures. Susceptibility to leakage is also low compared to Leclanché cell battery.
Safety is also another advantage of alkaline battery. Compared with acid-based and lead-based counterparts, this battery has lesser environmental impact. It does not require any special disposal methods. The compounds inside an alkaline battery do not pose serious health issues except from mild irritations.
However, compared to other batteries, alkaline batteries have disadvantages. For example, compared with a lithium ion battery, an alkaline battery is bulkier and heavier. Note that li-ion batteries have higher energy density.
Another disadvantage of alkaline battery is high internal resistance. Remember that internal resistance serves as a gatekeeper for determining runtime. A high internal resistance reduces the power output of a battery.
Leakage is also possible in alkaline batteries although Leclanché cell and zinc-carbon batteries have higher susceptibility. When left in devices for too long, the battery can leak and the leaked materials can corrode circuits.