Disposable batteries, also known as primary batteries, are called dry batteries if the electrolyte in the primary battery does not flow. Disposable is a type of battery that we often use, and it is also the battery with the widest range of applications, which cannot be reused. Since the battery reaction itself is irreversible or the reversible reaction is difficult to carry out, the battery cannot be charged for use after being discharged, that is, it cannot be used for a second time after one use.
Disposable batteries can be roughly divided into: carbon zinc-manganese batteries, alkaline zinc-manganese batteries, button batteries (button-type zinc-silver batteries, button-type lithium-manganese batteries, button-type zinc-manganese batteries), zinc-air batteries, primary lithium-manganese batteries Batteries, mercury batteries.
The working principle of carbon zinc-manganese battery, alkaline zinc-manganese battery and button zinc-manganese battery is the same. These three kinds of batteries use manganese dioxide as the positive electrode material of the battery, and zinc as the negative electrode material. When the battery is working, it converts chemical energy into electrical energy to supply the external circuit. In the chemical reaction, since zinc is more active than manganese, zinc loses electrons and is oxidized, and manganese gains electrons and is reduced.
The chemical formula of the working principle of some disposable batteries is as follows:
Zinc-manganese dry cell: (-)Zn|NH4Cl+ZnCl2|MnO2(c)(+)
Alkaline zinc-manganese batteries: (-)Zn|KOH|MnO2(c)(+)
Zinc-mercury battery: (-)Zn|KOH|HgO(+)
Zinc-Silver Battery: (-)Zn|KOH|Hg2O(+)
Alkaline zinc-air battery: (-)Zn|KOH|O2(c)(+)
The in-depth analysis of the working principle of zinc-manganese dry batteries is as follows:
The active materials of the battery are manganese dioxide and zinc, which are separated in space. Both of them are in contact with the aqueous solution of NH2Cl and ZnCl2. The electrolyte contains cations and anions, which are ionic conductors, but do not have electronic conductivity. sex.
When the zinc battery is in contact with the electrolytes NH4Cl and ZnCl2, the metal zinc will spontaneously transfer into the solution, and the oxidation reaction of zinc will occur. After the Zn2+ on the zinc electrode is transferred into the solution, the electrons are left on the metal, and the result is that the zinc electrode has a negative charge. It will attract the positive charge in the solution and generate a potential difference at both ends. This potential difference prevents Zn2+ from continuing to transfer into the solution, and at the same time prompts Zn2+ to return to the zinc electrode, forming a negatively charged ion on the zinc electrode and a positively charged ion on one side of the solution. Electric double layer.
A similar situation exists for manganese dioxide electrodes, except that the electrode is positively charged and the solution side is negatively charged.
Before the external circuit is connected, the above-mentioned dynamic balance exists on the electrodes. Once the external circuit is connected, the excess electrons on the zinc electrode flow to the manganese dioxide electrode, and the Mn4+ is reduced to Mn3+ on the MnO2 electrode.