Lithium batteries usually come in two shapes: cylindrical and square. The inside of the battery adopts a spiral winding structure, which is separated between the positive and negative electrodes with a very fine and highly permeable polyethylene film isolation material. The positive electrode includes a current collector composed of lithium cobalt oxide (or nickel lithium cobalt manganese, lithium manganate, lithium ferrous phosphate, etc.) and aluminum foil. The negative electrode consists of a current collector consisting of graphitized carbon material and copper foil. The battery is filled with an organic electrolyte solution. It is also equipped with a safety valve and PTC element (partially cylindrical use) to protect the battery from damage in the event of abnormal conditions and output short circuits.
The voltage of a single-cell lithium battery is 3.7V (3.2V for the positive electrode of lithium ferrous phosphate), and the battery capacity is not infinite, so it is often necessary to series and parallel the single-cell lithium battery to meet the requirements of different occasions.