Trong đầu những năm 1990, sự chú ý chuyển đến nickel-metal hydride (NiMH) và các bài viết so sánh cổ điển nickel cadmium (NiCd) với NiMH, những đứa trẻ mới về khối. Về tuổi thọ và độ chắc chắn, NiMH đã không thực hiện rất tốt khi được đặt chống lại các NiCd và tôi đã khá thẳng thắn về nó. Trong những năm qua, tuy nhiên, các NiMH cải thiện và ngày nay hóa học này thực hiện | Some prismatic cells are similar in size but are off by just a small fraction. Such is the case with the Panasonic cell that measures 34 mm by 50 mm and is mm thick. If a few cubic millimeters can be added for a given application the manufacturer will do so for the sake of higher capacities. The disadvantage of the prismatic cell is slightly lower energy densities compared to the cylindrical equivalent. In addition the prismatic cell is more expensive to manufacture and does not provide the same mechanical stability enjoyed by the cylindrical cell. To prevent bulging when pressure builds up heavier gauge metal is used for the container. The manufacturer allows some degree of bulging when designing the battery pack. The prismatic cell is offered in limited sizes and chemistries and runs from about 400mAh to 2000mAh and higher. Because of the very large quantities required for mobile phones special prismatic cells are built to fit certain models. Most prismatic cells do not have a venting system. In case of pressure build-up the cell starts to bulge. When correctly used and properly charged no swelling should occur. The Pouch Cell Cell design made a profound advance in 1995 when the pouch cell concept was developed. Rather than using an expensive metallic cylinder and glass-to-metal electrical feed-through to insulate the opposite polarity the positive and negative plates are enclosed in flexible heat-sealable foils. The electrical contacts consist of conductive foil tabs that are welded to the electrode and sealed to the pouch material. Figure 3-4 illustrates the pouch cell. The pouch cell concept allows tailoring to exact cell dimensions. It makes the most efficient use of available space and achieves a packaging efficiency of 90 to 95 percent the highest among battery packs. Because of the absence of a metal can the pouch pack has a lower weight. The main applications are mobile phones and military devices. No standardized pouch cells exist but rather each .
