Lithium Battery Protection
Lithium battery core overcharge to voltage is higher than 4.2 V, will start to produce side effects. Of charging the higher the pressure, the higher the risk also follow. Lithium batteries voltage higher than 4.2 V, the anode materials within less than half the number of lithium atoms left, store usually break down at this time, let the battery capacity to produce permanent decline. If continue to charge, due to the storage of the cathode has been full of lithium atoms, subsequent anode materials of lithium metal accumulation in the surface. These lithium atoms from lithium ion to the cathode surface to grow in the direction of the dendritic crystal. The lithium metal crystal through the diaphragm paper makes is negative short circuit. Sometimes in short circuit batteries before the first explosion, this is because in the process of overcharge, electrolyte materials can produce gas cracking, such as making the battery shell or pressure valve blow up broken crack, let oxygen in and accumulation in the lithium atoms on the surface of the cathode reaction, then exploded.
Therefore, lithium batteries, be sure to set the upper limit of voltage, can simultaneously to the battery life, capacity, and security. The ideal maximum charging voltage of 4.2 V. Lithium batteries discharge voltage will be lower limit. When the batteries voltage below 2.4 V, part of the material will begin to be destroyed. And because the battery self-discharge, put the more the longer the voltage is low, therefore, discharge when had better not to 2.4 V. Lithium battery discharge from 3.0 V to 2.4 V during this period, the release of energy accounted for only about 3% of the battery capacity. Therefore, is an ideal discharge cut-off voltage of 3.0 V. Charge and discharge, in addition to the limit of voltage and current limits can also be necessary. When the current is too large, lithium ions to enter the store, would gather in the material surface.