Manganese dioxide (MnO₂) is primarily used as a positive electrode (cathode) material in the following types of batteries:
1. Alkaline Batteries
Common Types: AA, AAA, C, D, and 9V alkaline batteries.
Role of MnO₂: Serves as the primary cathode material, reacting with zinc (anode) and potassium hydroxide (electrolyte).
Amount of MnO₂:
Typically constitutes ~35-45% by weight of the total battery.
For example, an AA alkaline battery contains ~8–10 grams of MnO₂.
2. Zinc-Carbon (Leclanché) Batteries
Common Types: Low-cost disposable batteries (AA, AAA, etc.).
Role of MnO₂: Acts as the cathode depolarizer, accepting electrons during discharge.
Amount of MnO₂:
Makes up ~30-40% by weight of the battery.
An AA zinc-carbon battery contains ~5–7 grams of MnO₂.
3. Lithium-Manganese Dioxide (Li-MnO₂) Batteries
Common Types: Coin cells (e.g., CR2032) and cylindrical lithium primary batteries.
Role of MnO₂: Serves as the cathode, with lithium metal as the anode.
Amount of MnO₂:
Typically ~40-60% by weight of the cathode.
A CR2032 coin cell contains ~0.3–0.5 grams of MnO₂.
4. Rechargeable Lithium-Ion Manganese Oxide (LiMn₂O₄, LMO) Batteries
Common Applications: Power tools, medical devices, and electric vehicles.
Role of MnO₂: Modified into spinel LiMn₂O₄ for reversible lithium intercalation.
Amount of MnO₂:
Cathode composition is ~50-60% LiMn₂O₄ (derived from MnO₂).
Key Notes
Primary (Non-rechargeable) batteries (Alkaline, Zinc-Carbon, Li-MnO₂) use MnO₂ as the main cathode material.
Rechargeable LiMn₂O₄ batteries use a modified manganese oxide structure.
The exact amount of MnO₂ depends on battery size and chemistry but generally ranges from 30% to 60% of the cathode mass.
