Lithium batteries
... 4 V and practical energy densities exceeding 200 W hr / kg. Li cells also have very long shelf-lives, and are extensively used as small cylindrical or button cells in low-rate devices such as watches and calculators, where they can operate for several years. The long shelf-lives also make them the best choice for pacemaker batteries. Some disadvantages of these cells are the decompositon of Li when contacted with ambient water or air, requiring sealed cells. The reaction of Li with water can produce hydrogen gas, and cells can be hazardous if punctured or improperly disposed. Nonaqueous electrolytes are employed, these are comprised of polar organic liquids (such as dimethyl ether or propylene carbonate) containing a dissolved lithium salt. The use of polymer-based electrolytes such as poly(ethylene oxide)/salt complexes has also been investigated in detail. About a dozen different cathodes have been used in commerci...