Alkaline Batteries Construction Working of Alkaline Battery

Batteries contain one or more electrochemical cells and provide portable electrical energy. Common consumer cells supply low voltage, but battery chemistry does not determine whether a cell is rechargeable. Standard zinc-manganese dioxide alkaline cells are primary cells and must not be recharged unless the product is specifically marked rechargeable. A Lead-acid battery is a separate rechargeable chemistry.
The modern cylindrical Alkaline battery was developed in the 1950s. A US patent filed in 1957 names Paul Marsal, Karl Kordesch and Lewis Urry as inventors of a primary alkaline manganese-dioxide dry cell for Union Carbide.

Lew Urry worked at the company’s Parma, Ohio, laboratory and contributed to the alkaline battery design. Service life relative to zinc-carbon depends on cell size, load, cutoff voltage, temperature and duty cycle, so one fixed multiplier does not apply to every device.

Alkaline Batteries

This article primarily describes the consumer zinc-manganese dioxide cell, not a replacement for lead-acid storage batteries. The principle of the alkaline battery is the electrochemical reaction between a zinc anode and manganese dioxide (MnO₂) cathode material. Its aqueous potassium hydroxide electrolyte is alkaline.

Advantages of Alkaline Battery

1. Higher usable energy than many zinc-carbon cells of the same standard size under comparable test conditions.
2. Suitable for both continuous and intermittent loads, although delivered capacity depends on the discharge schedule.
3. Available for low-, moderate- and high-drain devices, but usable capacity falls as continuous discharge current rises.
4. Operates across a specified temperature range; cold and heat still change voltage, capacity, shelf life and leakage risk.
5. A fresh cell can have low internal resistance, but the value depends on size, design, state of discharge and temperature.
6. Long product-specific shelf life when stored under the manufacturer’s stated conditions.
7. Sealed for normal use, although depleted, damaged, reversed or overheated cells can still leak or rupture.
8. Made in standardised consumer sizes, with exact dimensions set by the applicable designation.

Disadvantage of Alkaline Battery

Standard alkaline cells are not rechargeable, their terminal voltage falls during discharge and their usable capacity depends strongly on load and temperature. They can cost more than zinc-carbon cells, while other chemistries may perform better in high-drain or rechargeable uses. Select a cell from the device and battery manufacturers’ specifications.

Construction of Alkaline Battery

A typical cylindrical cell uses a steel can as the positive current collector and outer container. A compressed mixture of manganese dioxide (MnO₂) and conductive carbon contacts the inner wall and forms the cathode mix of the alkaline battery. A porous separator keeps that mix apart from the central gelled zinc anode while allowing ionic conduction through the potassium hydroxide electrolyte. Powdered zinc provides high reaction area. A brass collector pin connects the zinc gel to the negative terminal. The seal assembly electrically isolates the negative terminal from the positive can and includes safety features defined by the manufacturer. The steel can is not itself the MnO₂ cathode active material in this alkaline battery.

During discharge, zinc is oxidised at the anode and manganese dioxide is reduced at the cathode. Potassium hydroxide carries ions but is not consumed in the simplified overall reaction (MnO2 chemistry can proceed through intermediate phases).
A simplified anode half-reaction is:

A simplified cathode half-reaction is:

The resulting simplified overall reaction is:

A consumer alkaline cell has a nominal rating of 1.5 V. Fresh open-circuit voltage and the voltage under load depend on the exact product, temperature, state of discharge and current. An AA cell does not have a universal 700 mA rating; manufacturer discharge curves show how capacity and runtime change with the load and cutoff voltage.
The phrase types of alkaline battery can also refer broadly to other cells that use alkaline electrolytes.
The following legacy list contains different electrochemical systems, not variants of the primary zinc-manganese dioxide construction described above:

1. Nickel-iron (Edison), a rechargeable alkaline-electrolyte system.
2. Nickel-cadmium (Ni-Cd), a rechargeable system with chemistry and safety requirements distinct from nickel-iron.
3. Silver-zinc, a separate high-energy chemistry available in specialised cell designs.
4. Alkum battery, a legacy term that requires a source-specific chemistry definition before use.

Primary consumer alkaline cells are normally sealed. Rechargeable nickel-iron, nickel-cadmium and silver-zinc products have their own venting, sealing and maintenance designs; do not transfer one system’s classification to another.
Pocket-plate terminology applies to some industrial rechargeable alkaline cells, not to the powdered-electrode cylindrical zinc-manganese dioxide cell shown above.

Uses of Alkaline Batteries

Primary zinc-manganese dioxide cells power products such as clocks, remote controls, radios, toys, lights and personal electronics, subject to each device’s load profile. Rechargeable nickel-iron and nickel-cadmium batteries have served specialised industrial and transport duties, but they are different chemistries with separate charging, maintenance, transport and disposal rules. Do not select an aviation or industrial alkaline battery from this general description; use the approved equipment and battery manufacturer documentation.