The biggest feature of lithium batteries is their high specific energy. What is specific energy? Specific energy refers to energy per unit weight or unit volume. The specific energy is expressed in Wh/kg or Wh/L. Wh is the unit of energy, W is watt, h is hour; kg is kilogram (weight unit), and L is liter (volume unit). Here is an example to illustrate: the No. 5 nickel-cadmium battery has a rated voltage of 12V and its capacity is 800mAh, and its energy is 096Wh (12V×08Ah). The same size of the No. 5 lithium-manganese dioxide battery is rated at 3V, and its capacity is 1200mAh, and its energy is 36Wh. The volume of these two batteries is the same, the specific energy of the lithium-manganese dioxide battery is 375 times that of the nickel-cadmium battery!
A No. 5 nickel-cadmium battery weighs about 23g, while a No. 5 lithium-manganese dioxide battery weighs about 18g. One lithium-manganese dioxide battery is 3V, and two nickel-cadmium batteries are only 24V. Therefore, when the lithium battery is used, the number of batteries is small (the portable electronic product is reduced in size and weight), and the battery has a long working life.