Zinc Carbon batteries

The need for energy supply has been one of the concerns of mankind since the beginning of time, and the invention of the battery was a suitable and somewhat revolutionary answer to this human concern. Today, most of the devices used by humans are designed to be portable, so the need for batteries to supply energy is increasing day by day.

Zinc Carbon batteries, sometimes known as Leclanché batteries, are considered to be the first commercial batteries. A man named ” Carl Gassner” invented and patented the dry cell.

Gessner’s invention evolved in a few years and in 1900, its prototype was exhibited at the World’s Fair in Paris. By the end of the 20th century, the capacity of these types of batteries increased significantly and reached 4 times the capacity of the original samples.

Zinc Carbon batteries have a large share of the customer market due to their reasonable price, not being dangerous for the environment, being available in all regions and stores, etc.

General characteristics

The items mentioned in the following table are among the features of zinc carbon batteries:

• Simple yet reliable technology
• Reasonable consumer price compared to other technologies
• Accessible worldwide to consumers
• Compatibility with all types of household appliances
• Wide range of dimensions
• sufficient shelf life (about 3 years)

Structure and chemical compounds

Zinc carbon batteries consist of three main parts: anode, cathode and electrolyte. A zinc anode, a manganese dioxide cathode, and an ammonium chloride or zinc chloride electrolyte dissolved in water, make up the zinc carbon cell. The cathode mixture is often a wet mixture of special carbon black, manganese dioxide powder, an electrolyte, and a solution. To prevent short circuit between anode and cathode, a paper separator is installed in the battery.

The general structure of the cell

In this section, the general structure of zinc carbon batteries based on the products of “Sam Arash Parse” company is explained.

Cylindrical battery: a zinc container (anode) forms the body of the battery. In the next step, the inner wall and the bottom of the container are completely covered with a paper separator. Separating paper is impregnated with ammonium chloride (NH4Cl) and a thickening agent.

This combination creates an aqueous electrolyte paste. A paper separator prevents the zinc vessel (anode) from contacting the cathode, which is a mixture of powdered carbon (usually graphite powder) and manganese (IV) oxide (MnO2). This powder mixture is placed around a carbon rod.

Carbon is the only practical conductive material for this structure because any metallic conductive material will corrode quickly in contact with these salt-based solutions in the positive electrode. The carbon rod is slightly porous, which allows charged hydrogen atoms to form hydrogen gas.

The ratio of manganese dioxide and carbon powder in the cathode paste affects the characteristics of the cell: more carbon powder reduces the internal resistance, while more manganese dioxide improves the storage capacity.

Finally, after adding the glue, the metal piece with appendages, which we know as the positive pole of the battery, is placed in its place and sealed so that this closed system can supply the energy required by the circuit when being placed in a closed circuit.

Chemical reactions inside the cell:

The following chemical reactions occur in a carbon-zinc cell:

• Ammonium chloride electrolyte

  The oxidation half-reaction at the anode:

Zn + 2 Cl− → ZnCl2 + 2 e−

Reduction half-reaction at the cathode:

2 MnO2 + 2 NH4Cl + H2O + 2 e− → Mn2O3 + 2 NH4OH + 2 Cl−

And the overall final reaction is as follows:

Zn + 2 MnO2 + 2 NH4Cl + H2O → ZnCl2 + Mn2O3 + 2 NH4OH

• Zinc chloride electrolyte

If zinc chloride electrolyte is used instead of ammonium chloride, the oxidation half-reaction at the anode is the same as before

The oxidation half-reaction at the anode:

Zn + 2 Cl− → ZnCl2 + 2 e−

Reduction half-reaction at the cathode:

During this half-reaction, zinc hydroxide and manganese (III) oxide are produced.

2 MnO₂ + ZnCl₂ + H₂O + 2 e⁻ → Mn₂O₃ + Zn(OH)₂ + 2 Cl⁻

And the overall final reaction is as follows:

Zn + 2 MnO₂ + H₂O → Mn₂O₃ + Zn(OH)₂

Side reactions and discharge of active chemicals increase the internal resistance of the battery, which causes the terminal voltage to decrease under load.

Zinc chloride cells: Heavy duty

Zinc chloride cells, which are usually known as heavy-duty, super-heavy-duty, or extra-heavy-duty, are actually an improved model of zinc carbon cells. The use of raw materials with higher purity leads to longer life and better output voltage stability in these types of cells. This change has caused the life of this battery to increase by 2 to 4 times compared to the primary zinc carbon models.

Performance Characteristics

• Voltage: The nominal voltage of this type of cell is 1.5 volts, but in reality, the standard range of initial voltage is between 1.5 and 1.73 volts. When the cell voltage drops to 0.9 volts, the battery is considered as “discharged”.
• Internal resistance: The internal resistance of this type of cell is between 1 and 2 ohms in charged state. Discharging the battery causes the internal resistance to gradually increase.
• Environmental conditions: for the batteries to function properly, the ambient temperature must be between -15 and 55 degrees Celsius. The most favorable temperature for the performance of small intervals is close to room temperature, and at temperatures below 0 degrees Celsius, battery performance is disrupted. The optimal humidity for these batteries is between 15 and 55 percent.

Battery applications

Due to the high variety of dimensions, sizes and shapes of this type of cell, this cell is widely used in domestic applications. Including

• clocks
• Toys with low consumption
• Radio
• remote controls
• Flashlights

It should be noted that these batteries are not used for high power drain devices due to their lower capacity in comparison to other types of cells, such as alkaline cells.

battery life

Zinc carbon cells do not last long. The reason why these cells have a shorter lifespan than other types of primary cells is that zinc anode, which shapes the battery can, is attacked by ammonium chloride. Oxidized zinc metal changes into zinc ions and this chemical reaction causes the cell wall to become thinner and thinner. When the zinc casing becomes thin enough, zinc chloride begins to leak out of the battery. The outcome is that these batteries cannot be stored for long periods unused.

Environmental effects:

How to dispose of this type of battery depends on the country where you live. The United States classifies this type of cell as hazardous waste. It is strongly recommended not to dispose this type of battery with other waste. There are centers that collect used batteries and send them for recycling. The best way to dispose of the battery is to separate it from other waste in a separate bag.