For batteries, the size matters a lot. The more capacity a battery has, the longer it can work. The problem rest in that the inner space of laptops is limited, therefore, each millimeter maters a lot. Many laptop manufactures want to stuff as many batteries cells as possible in detachable battery pack, resulting in several problems: first, the shape of Li-ion batteries is fixed cylindrical—like ordinary AA batteries, serving to change hardly the thickness of laptops; in addition, the room between batteries could not be utilized fully. To prolong the longevity of batteries in the same lightening the thickness and weight of laptops, the scientists and engineers make use of Li-ion batteries, which can be tailored in answer for super-thin body of laptops.