How Do Alkaline Batteries Work

What are Alkaline Batteries?

“An alkaline battery is a type of primary battery whose energy is derived from the reaction of zinc metal and manganese dioxide. It is also a disposable battery.”

The alkaline battery gets its name from the fact that it uses an alkaline electrolyte of potassium hydroxide (KOH) rather than the acidic ammonium chloride (NH₄Cl) or zinc chloride (ZnCl₂) electrolyte used in zinc-carbon batteries. Other battery systems use alkaline electrolytes as well, but the active materials for the electrodes are different.

Alkaline batteries have a higher energy density and a longer shelf life than zinc-carbon batteries of the Leclanché cell or zinc chloride types while providing the same voltage.

Table of Contents

• Structure of an Alkaline Battery
• Construction of an Alkaline Battery
• Working of an Alkaline Battery
• Types of Alkaline Battery
• Applications
• Frequently Asked Questions – FAQs

Structure of an Alkaline Battery

To generate electricity, a typical battery requires three components:

• Anode
• Cathode
• An electrolyte

Components of Alkaline Battery

• Steel shell
• Other important accessories: Negative component- primarily made up of a sealing ring, a copper needle, and a base.
• Steel can
• Separator paper
• Conductive graphite
• Cathode mix
• Conductive graphite
• Cathode mix
• Collector nail
• Sealing plug
• Sealant
• Negative cap

Construction of an Alkaline Battery

• The battery’s body is made of a hollow steel drum. This drum contains all of the battery’s materials and also serves as the cathode.
• The battery’s positive terminal protrudes from the top of this drum.
• The inner peripheral surface of the empty cylindrical drum is moulded with fine-grained manganese dioxide (MnO₂) powder mixed with coal dust. This moulded mixture serves as the alkaline battery’s cathode mixture.
• A paper separator is placed on the inner surface of the thick layer of cathode mixture. Inside this paper separator, the central space is filled with zinc powder and a potassium hydroxide electrolyte.
• The zinc acts as an anode, and its powder form expands the contact surface.
• The electrolyte is held in place between the cathode (MnO₂) and the anode by a paper separator soaked in potassium hydroxide (Zn).
• To collect the negative charge, a metallic pin (preferably made of brass) is inserted along the central axis of the alkaline battery. This is known as a negative collector pin. This pin comes into contact with a metallic end-sealed cap.
• A plastic cover just inside the Metallic end sealed cap electrically separates the positive steel drum and negative end cap of an alkaline battery.

Working of an Alkaline Battery

A cell of an alkaline battery is a section of the battery. In a chemical power supply, a dry battery is the primary battery. It’s a disposable battery of some sort. It converts chemical energy into electrical energy by using manganese dioxide as the positive electrode and zinc cylinder as the negative electrode to power an external circuit. Because zinc is more active than manganese in the chemical reaction, zinc loses electrons and is oxidised, whereas manganese gains electrons and is reduced.

First half reaction,

Zn (s) + 2HO^– (aq) → Zn(s) + H₂O (l) + 2e^– (e° = – 1.28 V)

Second half reaction,

2MnO₂ (s) + H₂O (l) + 2e^– → Mn₂O₃ (s) + 2HO^– (aq) (e° = + 0.15V)

Overall reaction,

Zn (s) + 2MnO₂ (s) ⇌ Mn₂O₃ + Zno (s) (e° = 1.43 V)

Sometimes alkaline batteries occasionally leak or explode. This happens due to an internal short circuit. On removing the sealing ring, the electric fluid inside will flow out.

Note- If the fluid comes into contact with the skin, immediately wash it with water.

Since the air volume in alkaline batteries is very small, one should not be concerned about explosions; at most, the bottom of the negative electrode rushes out, usually within 20 cm, causing no serious injury to personnel.

There is no spontaneous combustion substance in alkaline batteries because alkaline batteries, unlike lithium batteries, do not spontaneously ignite.

Types of Alkaline Batteries

1. There are four types of batteries based on the composition of the active materials in the plates. These are their names:

• Nickel iron (or Edison).
• Nickel- cadmium (or Nife).
• Silver zinc.
• Alkum battery.

2. These batteries can also be classified as sealed or non-sealed depending on how they are assembled.

3. The alkaline battery is also classified as an enclosed pocket or open pocket battery based on the design of the plates.

Applications

Toys, flashlights, portable electronic circuits, breadboard circuits and digital cameras.

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