Lithium-ion primary batteries

Lithium has a number of advantages over other materials for battery manufacture. It is the lightest tme metal, and it also has a high electrochemical reduction potential, that is, it occurs at the bottom of Table 9.1. There is one disadvantage in using lithium in that it is very reactive, a feature that poses problems not only in manufacture but also in the selection of the other battery components. Despite this, there are a large number of lithium-based primary cells available, both in traditional cylindrical form and as button and flat coin cells. 

The cell reactions are poorly understood, but can be written schematically as follows. 

Cathode reaction (reduction, electron consumption) Mn02(s) + — MnO (s) 

The cell potential is about 2 V. A car battery consists of (usually) six cells in series (a battery of cells), to give 12 V. Sulphuric acid is used up during operation, so the state of charge of the battery can be estimated by measuring the concentration of the acid, usually via density. 

The cell-charging reaction is the reverse of the discharge reaction, and to charge a battery the cell reaction is simply driven backwards by an imposed external voltage. 

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