Cylindrical lithium batteries are divided into different systems of lithium iron phosphate, lithium cobalt oxide, lithium manganate, cobalt-manganese hybrid, and ternary materials. The outer shell is divided into two types: steel shell and polymer. Different material systems have different advantages. At present, the cylinders are mainly steel-shell cylindrical lithium iron phosphate batteries, which are characterized by high capacity, high output voltage, good charge and discharge cycle performance, stable output voltage, large current discharge, stable electrochemical performance, and use Safe, wide operating temperature range, and environmentally friendly, it is widely used in solar lamps, lawn lamps, back-up energy, power tools, toy models.