Types of primary cell

Here are the main types of primary cells:

1. Leclanché Cell (Zinc-Carbon Battery):

   • Anode: Zinc (Zn)
   • Cathode: Manganese dioxide (MnO₂)
   • Electrolyte: Ammonium chloride (NH₄Cl) paste
   • Reaction: Zn → Zn²⁺ + 2e⁻ (anode); 2MnO₂ + 2NH₄⁺ + 2e⁻ → Mn₂O₃ + 2NH₃ + H₂O (cathode)
   • Notes: Older technology, relatively low cost, suitable for low-drain devices.

2. Alkaline Battery:

   • Anode: Zinc (Zn) powder
   • Cathode: Manganese dioxide (MnO₂)
   • Electrolyte: Potassium hydroxide (KOH) (alkaline)
   • Reaction: Zn + 2OH⁻ → ZnO + H₂O + 2e⁻ (anode); 2MnO₂ + H₂O + 2e⁻ → Mn₂O₃ + 2OH⁻ (cathode)
   • Notes: Higher energy density and longer shelf life than Leclanché cells, common in portable electronics.

3. Lithium Primary Cells:

   • Anode: Lithium metal (Li)
   • Cathode: Various materials like manganese dioxide (MnO₂), thionyl chloride (SOCl₂), or sulfuryl chloride (SO₂Cl₂)
   • Electrolyte: Organic solvents or solid electrolytes
   • Reaction: Li → Li⁺ + e⁻ (anode); Cathode reactions vary depending on the specific chemistry.
   • Notes: Very high energy density, long shelf life, wide operating temperature range, used in high-tech devices, watches, and medical implants.

4. Silver-Oxide Battery:

   • Anode: Zinc (Zn)
   • Cathode: Silver(I) oxide (Ag₂O)
   • Electrolyte: Potassium hydroxide (KOH)
   • Reaction: Zn + 2OH⁻ → ZnO + H₂O + 2e⁻ (anode); Ag₂O + H₂O + 2e⁻ → 2Ag + 2OH⁻ (cathode)
   • Notes: Stable voltage output, high energy density, often used in watches and small electronics.

5. Mercury Battery:

   • Anode: Zinc (Zn)
   • Cathode: Mercury(II) oxide (HgO)
   • Electrolyte: Potassium hydroxide (KOH)
   • Reaction: Zn + 2OH⁻ → ZnO + H₂O + 2e⁻ (anode); HgO + H₂O + 2e⁻ → Hg + 2OH⁻ (cathode)
   • Notes: Historically used in hearing aids and cameras, but largely phased out due to environmental concerns (mercury toxicity).