The lithium battery can be divided into two classes: secondary and primary ones. The primary battery can only primarily transform the chemical energy into the electrical one, but not the reverse, it should not be recharged ,such as the Li-MnO2 primary battery, lithium thionyl chloride battery, etc.. The secondary battery is also the rechargeable battery, which can transform the electrical energy into chemical energy and put it in storage; the reverse transformation will be made when it is used, such as the li-ion mobile phone batteries.

The outstanding feature of lithium battery is the high energy density, that is, the high energy of per unit of weight or volume. The gravimetric energy is shown by wh/kg and volumetric energy density by wh/l. wh -the unit of energy, w refers to voltage, and h refers to hour; kg is kilograms (the unit of weight) and L is liter(the unit of volume). For instance, the rating voltage of 5# nickel cadmium cell is 1.2 V, the capacity is 800mAh, while the energy is 0.96Wh(1.2V×0.8Ah). In contrast, as for the 5# Li-MnO2 battery of the same size, the rating voltage is 3v, the capacity 1200mAh and energy 3.6Wh. Although the two batteries have the same volume, the energy of the latter is 3.75 times that of the former .

The application of the lithium battery includes the palmtop, the portable computer, PDA, communication instruments, cameras, satellites, rockets, fish torpedo and other apparatuses.