What is the damage of overcharge and overdischarge of lithium ion battery
Overcharge, to put it bluntly, is overcharged, that is, after the battery is fully charged, recharge it.
When the battery is fully charged, recharge to a certain level. The vapor caused by the dissolution of the lithium-ion battery electrolyte in the lithium iron phosphate battery will cause the battery to swell and even smoke. In this way, the battery can no longer work normally. Just like a balloon, the balloon will be blasted in the same way after it is filled with air.
Some customers, in order to better the beauty of their products, or to better meet the requirements of the stamping die of the product, usually only purchase batteries and design their own lithium-ion battery protection boards, which is also very easy to cause overcharging. On the one hand, because their battery technology expertise is not high, the experimental equipment is out of date, and the important parameters of the design method for overcharge maintenance are different; on the other hand, because the quality of the batteries produced by different battery cell manufacturers is different, the common lithium raw materials are also different. It is not the same. If they can’t tell the difference and use the same processing technology to design and manufacture important parameters for overcharging and maintenance, it is also very easy to make mistakes and omissions, resulting in overcharging.
Naturally, once or twice overcharge, the damage to the battery is not too great, and the customer experience is not deep, but after a long time and the frequency of overcharge increases, the battery will deteriorate due to the mutual change of quality until it cannot be charged. , Also can not be released, the result is obvious.
To put it bluntly, over-discharge means that the battery has exhausted the internally stored power consumption. After the working voltage drops to a certain value, it is discharged again, which leads to over-discharge. Generally, the discharge cut-off voltage is determined based on the amount of discharge current, that is, the critical value of over-discharge. The working voltage value is the critical value of over-discharge. For 3.7V lithium-ion batteries, the 0.2C-2C discharge is generally set to 3.0V, and the discharge is above 3C. , Such as 4C or 10C discharge, set to 2.4V.
Over-discharge of the battery will usually cause a devastating bitter effect on the battery, especially the over-discharge of large current, or continuous over-discharge, which is more harmful to the electrical performance of the battery. This is like a person who loses more than three to five hundred mL of blood at one time, which is not easy to harm people's physical and mental health. However, once the blood loss is too much, the person's normal body functions cannot be maintained. If it reaches a certain level, the person will die. . For batteries, over-discharge will increase the gas pressure of the battery, and the cross-purpose use of positive and negative active materials will be damaged. Even if it is rescued by charging, it is difficult to repair all. Of course, the volume has a significant attenuation coefficient, and the attenuation coefficient reaches a certain level. Death, there is no way to resurrect from death.