Why lithium battery's capacity will become less ?（2）

External cause:

(1) When the lithiun battery is charging and discharging rapidly, the current density is too large, the negative polarization, lithium deposition will be more obvious, so that the copper foil and carbon active material at the border of the copper foil brittle, easy to produce cracks The The spontaneous winding of the batteries is limited by the fixed space, and the copper foil can not be freely extended to produce the pressure. Under the action of the pressure, the original crack spreads, because the expansion space is not enough, the copper foil breaks.

(2) The thermal stability of the organic electrolyte is the first problem to be considered when the temperature is significantly higher than room temperature, which includes both the thermal stability of the organic electrolyte and the thermal stability of the electrolyte interaction of the electrode The It is generally believed that the effect of the reaction of the positive / organic electrolyte on the safety of the KON ion battery is the main factor. Because of the positive electrode, the reaction kinetics of the electrolyte is very fast, so the whole heat resistance of the battery is controlled. If the ambient temperature of the battery is sufficient to cause a positive electrode electrolyte reaction, it will cause the battery to run out of heat, or even fire, explosion. The size of the discharge current directly affects the discharge capacity of the lithium ion battery. In the high current discharge, there is not only the serious electrolyte interface polarization, but also the active body that is embedded ions and diffusion polarization in the electrode.

(3) Long-term depth of charge and discharge to be transferred from the internal structure, one will cause the electrolyte excessive volatilization, and second, the lithium battery negative reaction to make its dielectric film changes caused by de-embedding capacity, the formation of capacity Permanent loss; charging mainly from the voltage stability and to the late night grid voltage rise, which has stopped charging the charger, the voltage rises, will continue to charge, resulting in battery overcharge lead to positive material structure changes in capacity loss, Oxygen and electrolyte oxidation reaction and then explosion; electrolyte organic solvent / electrolyte lithium salt decomposition; negative lithium ion over discharge may lead to negative electrode copper electrode dissolved, the cathode to form copper dendrite.

(4) Vibration and collision is generally the cause of the process, such as welding firm or not, whether the internal circuit design is reasonable and so on.