In order to avoid over-discharge or over-charging of the battery due to improper use, a triple protection mechanism is provided in the single-cell lithium ion battery. First, the switching element is used. When the temperature inside the battery rises, its resistance value rises. When the temperature is too high, the power supply will be automatically stopped. Second, the appropriate separator material is selected. When the temperature rises to a certain value, The micron-sized micropores on the separator will be dissolved automatically, so that the lithium ions will not pass, and the internal reaction of the battery will stop. The third is to set the safety valve (that is, the venting hole at the top of the battery). When the internal pressure of the battery rises to a certain value, the safety valve Automatically open to ensure the safety of the battery.