Polarization
A major factor reducing the lifetime of primary cells is that they become polarized during use. This means that hydrogen accumulates at the cathode and reduces the effectiveness of the cell.
To reduce the effects of polarization in commercial cells to extend their lives, chemical depolarization is used; that is, an oxidizing agent is added to the cell, to oxidize the hydrogen to water. Manganese dioxide is used in the Leclanché cell and zinc–carbon cell, and nitric acid is used in the Bunsen cell and Grove cell.
Attempts have been made to make simple cells self-depolarizing by roughening the surface of the copper plate to facilitate the detachment of hydrogen bubbles. with little success. Electrochemical depolarization exchanges the hydrogen for a metal, such as copper (e.g., Daniell cell), or silver (e.g., Silver-oxide cell).
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