When lithium batteries are charged and discharged, complex electrochemical reactions usually occur inside the battery. Due to the irreversibility of the reaction, the battery electrode active material and cyclable active lithium ions are often reduced. And it causes the battery capacity to drop and the resistance to rising, causing the battery to age and decline.
The aging of lithium batteries in the actual use process is divided into two categories: cyclic aging and calendar aging. Cyclic aging is the irreversible capacity loss during the charge-discharge cycle. The main influencing factors are charge-discharge current, cut-off voltage, state of charge (SOC), temperature, depth of discharge (DOD), etc. To achieve safe and fast charging, It is of great significance to study the mechanism of battery aging. In order to provide more cycle life cell, Greenbatt develop a 8000 cycle 50Ah cell for ESS battery.
Battery aging is mainly due to the increase of internal resistance and the decline of capacity， which are determined by the internal electrochemical properties of the battery. The reasons for battery aging are corrosion and dissolution of electrode active materials, structural changes, active material particle cracking, etc. These lead to the damage of the positive and negative electrodes, the growth and thickening of the solid electrolyte interphase (SEI), the loss of active lithium ions caused by the lithium deposition of the negative electrode, etc. These factors will lead to the decline of the maximum usable capacity of the battery. Usually 3.2V50Ah cell, the rated capacity is about 52Ah to decline influence of capacity decline.
There are 3 stages of battery capacity decay:
1.The battery capacity decay is mainly due to the formation of the SEI film.
2.During the aging process of the battery, the proportion of cathode material declines increases, but the consumption of active lithium ions is the main reason.
3.The main reason for battery aging and decay is the decay of cathode materials, and the change of anode will accelerate battery aging.
