Cathode is a mixture of high purity electrolytic manganese dioxide and carbon conductor. Anode is a gelled mixture of zinc powder and electrolyte. Separators of specially selected materials prevent migration of any solid particles in the battery. Steel can confines active materials and serves as the cathode collector. Brass collector serves as the anode collector. Positive and negative covers provide contact surfaces of nickel-plated steel. Non-conductive plastic film label electrically insulates the battery. Nylon seal provides a safety venting mechanism.
Electrochemistry:
An alkaline battery produces electricity when the manganese dioxide cathode is reduced and the zinc anode becomes oxidized. The equation for a simple alkaline cell reaction is as follows:
Zn + 2MnO2 + H2O → ZnO +2MnOOH
During this reaction, water (H2O) is consumed and hydroxyl ion (OH-) are produced by MnO2 cathode under following reaction:
2 MnO2 + 2 H2O+ 2 e → 2MnOOH + 2OH-.
At the same time, the anode is consuming hydroxyl ions and producing water:
Zn + 2 OH- →ZnO +H2O + 2 e.
The electrons (e) generated during the reaction are used to power devices. The rate of the reaction is dependent on the quality of the raw materials and availability of water and hydroxyl ions during reaction. A battery is designed to keep the cathode and anode separated to prevent the reaction from occurring. The stored electrons will only flow when the circuit is closed. This occurs when the battery is placed in a device and the device is turned on. This principle is the same as turning on and off a light switch in a house.
When the circuit is closed, the stronger attraction for the electrons by the manganese dioxide will pull the electrons from the zinc anode electrode through the wire in the circuit to the cathode electrode. This flow of electrons through the wire is electricity and can be used to power applications.
Alkaline batteries typically have a sloping discharge curve. Most devices are designed to operate within a voltage range (for example from 1.6 volts to 0.9 volts per cell) to accommodate this sloping discharge characteristic. The sloping discharge in alkaline batteries is primarily due to the increase in battery internal resistance due to reaction byproducts forming on the electrode surfaces and decrease availability of the fuels (i.e., water). Hydrogen gas is a byproduct of the chemical reaction in all alkaline batteries.: