Sony developed a new thin and lightweight battery by replacing the conventional electrolyte with a new gel polymer electrolyte. Because gel polymer electrolyte has a superior advantage of anti-leakage characteristics, the batteries need to be enclosed with hybrid laminated films. This helps modify the battery shape fixation due to conventional metal enclosure and create a variety of battery sizes. Consequently Sony was able to achieve a 3.8 mm - an ideal shape for portable use. Hybrid laminated film enclosure is lighter than metal enclosure of conventional battery, and allows additional weight-energy density when compared to conventional batteries of equal capacity.