Failure in Charging and Discharging Process
Inevitably, in the process of use, batteries are often overcharged.
Relatively speaking, there are fewer cases of over-discharging, but the heat released in the process of overcharging or over-discharging tends to gather inside the battery, which will further make the battery temperature rise and affect the service life of the battery.
Even it will increase the possibility of battery fire or explosion.
Even under normal charging and discharging conditions,
with the increasing number of cycles, the capacity inconsistency of internal cells will increases, and a cell with the least capacity will also experience the process of overcharge and over-discharge.
Although in different charging states, compared with other cathode materials, heat stability of LiFePO4 is the best. Nevertheless, overcharging still arises unsafe risk.
Under overcharge condition, one of the mainly reasons about batteries’ failure is internal short circuit caused by lithium crystal branches.
With the appearance of lithium crystal branches, the reaction between lithium and electrolyte generates an increasing surface film, which not only consumes more active lithium, but also makes it more difficult for lithium to diffuse into the graphite cathode.
In turn, it will further promote the deposition of lithium on the surface of the cathode, causing a further decrease in capacity.
In addition, metal impurities (especially Fe) are often considered to be one of the main causes of battery overcharge failure. During the overcharge/discharge cycle, Fe gets redox reaction. When the battery is overcharging or discharging, Fe crystal branches will be formed at both positive and negative electrodes, which will pierce the diaphragm and form Fe bridges, causing a micro-short circuit in the battery. And the obvious phenomenon accompanying the micro-short circuit in the battery is the continuous increase in temperature after overcharge.
In all, LiFePO4 battery’s is delicate. We need to carefully use them and know right using and storing methods in order to save our life and money.
According to above four parts, we can conclude some tips about how to protect our LiFePO4 batteries.
Let’s have a try:
- Do not put them into humid and high temperature places
- Do not use them in humid and high temperature places
- Do not over charge and over discharge
- Do not charge them with too high or too low voltage
- Choose good brand of battery
If you have any other ideas about how to protect our LiFePO4 batteries. We are welcome for your comments.