Not a few times we heard about MacBook batteries that swelled or batteries of iPod or iPhone terminals that exploded. For Apple, this problem is more than serious, so the company's engineers have developed a new one battery model which have a special mechanism that prevents them from exploding. Basically, the new batteries developed by Apple have a pressure release system so that when pressure builds up inside the battery, it will be released through certain holes specially designed to fail when subjected to a certain pressure. The battery cells could be covered with some kind of bag that when subjected to strong pressure would break and release the pressure.
A potential safety issue could arise if there is a gas buildup within a rechargeable lithium battery cell. This could occur, for example, if the cell is overcharged, if there is a short within the cell, or if the cell is left uncharged for a significant period of time. This type of gas buildup could potentially cause the battery cell to swell or even explode, which could seriously damage the portable electronic device, and may even start a fire. To alleviate this problem, cylindrical lithium-ion battery cells are often equipped with a vent valve to release the internal pressure in the battery cell when a gas buildup occurs. However, there are no comparable pressure-relief mechanisms for lithium-polymer batteries, which are becoming increasingly popular in portable electronic devices. A lithium-polymer battery is typically enclosed in a flexible pouch, which is lightweight and inexpensive to manufacture. However, no pressure-relief mechanism has been developed for these pouches so far.
The problem comes from the fact that in most batteries for mobile terminals there is a certain amount of gas that could force the battery to swell or explode. The new batteries developed by Apple could be protected from such a thing thanks to the bag that the company designed, the bag that would release the gas when needed. The idea is very complex, but it could be of great help to the company that has had quite a few problems due to batteries in recent years.
Apple's patent application outlines a battery cell which includes a weakness for relieving pressure. This battery cell may include a jelly roll comprising layers which are wound together, including a cathode with an active coating, a separator, and an anode with an active coating. The jelly roll may also include a first conductive tab coupled to the cathode and a second conductive tab coupled to the anode. The jelly roll, according to Apple, is enclosed in a flexible pouch, in which the first and second conductive tabs extend through seals in the pouch to provide terminals for the battery cell. This pouch includes a weakness which yields when internal pressure in the pouch exceeds a threshold to create a hole which releases the internal pressure.
