Zinc chloride cell

The zinc chloride cell , also known colloquially as the zinc chloride battery, is a special type of galvanic cell . Its main ingredients are zinc chloride and manganese dioxide . This type of battery was one of the most widely used types of batteries until the late 1970s. Today it is still occasionally used for flashlights , toys and small electrical appliances, but has been almost completely replaced by the more powerful alkali-manganese cell . The most common shape was the round R20 / UM-1 / "Mono" battery.

development

The zinc chloride cell is a further development of the Leclanché element . Compared to its predecessor, it is more expensive to produce and needs more protection against drying out. The zinc chloride cell, however, supplies a more constant voltage , has a potentially higher capacity and is relatively leak-proof, which means that the advantages outweigh the total.

Reactions

• Anode reaction (negative pole):

${\displaystyle \mathrm {Zn\longrightarrow Zn^{2+}+2\ e^{-}} }$

Oxidation of zinc

• Cathode reaction (positive pole):

${\displaystyle \mathrm {2\ MnO_{2}+2\ H_{2}O+2\ e^{-}\longrightarrow 2\ MnOOH+2\ OH^{-}} }$

Reduction of manganese dioxide to manganese oxide hydroxide

• Overall reaction:

${\displaystyle \mathrm {4\ Zn+8\ MnO_{2}+ZnCl_{2}+9\ H_{2}O\longrightarrow [ZnCl_{2}*4\ ZnO*5\ H_{2}O]+8\ MnOOH} }$

• Complex formation:

${\displaystyle \mathrm {4\ Zn+H_{2}O+8\ OH^{-}+Zn^{2+}+2\ Cl^{-}\longrightarrow [ZnCl_{2}*4\ ZnO*5\ H_{2}O]\downarrow +8\ e^{-}} }$

Technical specifications

In the unloaded state, the cell voltage is 1.5 V. During operation, however, it drops because the zinc complex [ZnCl ₂ * 4ZnO * 5H ₂ O] is deposited on the surfaces of the electrodes and thus increases the resistance in the circuit.

literature

• Jochen Fricke: Zinc chloride batteries and redox cells - electrochemical storage systems for cars and renewable energy sources . Physics in our time , p. 157–159 , doi : 10.1002 / piuz.19800110506 (issue 11 (5)).

Footnotes

1. ↑ The higher capacity is achieved by lowering the internal resistance. This is possible by increasing the volume of the brown stone doll ( manganese dioxide ). Construction features ( zinc chloride painted on paper ) also ensure that self-discharge is minimal.
2. ↑ The fact that the reaction consumes water increases the security against leaks.