The Effect of Moisture on Lithium Batteries

1. The battery is swollen and leaking

If the water content in the lithium-ion battery is excessive, it will chemically react with the lithium salt in the electrolyte to form HF:

Hydrofluoric acid (HF) is a very corrosive acid that can be very damaging to battery performance:

HF destroys the SEI membrane (Solid-Electrolyte-Interface) inside the battery and reacts with the main components of the SEI membrane:

Finally, LiF precipitation is generated inside the battery, so that the lithium ions undergo an irreversible chemical reaction in the negative electrode piece of the battery, and the active lithium ions are consumed, and the energy of the battery is reduced.

When there is enough water, more gas is generated, and the pressure inside the battery will increase, which will cause the battery to be deformed by force, and there will be dangers such as bulging and leakage of the battery.

Most of the battery swelling and opening the cover encountered in the use of mobile phones or digital electronic products on the market are caused by high moisture and gas production swelling inside the lithium battery.

2.The internal resistance of the battery becomes larger

The internal resistance of the battery is one of the most important performance parameters of the battery, and it is the main indicator to measure the difficulty of the transmission of ions and electrons inside the battery, which directly affects the cycle life and operating state of the battery. The smaller the internal resistance, the less voltage is occupied when the battery is discharged, and the more energy is output.

When the water content increases, POF3 and LiF precipitation will be generated on the surface of the SEI membrane (Solid-Electrolyte-Interface) of the battery, which will destroy the compactness and uniformity of the SEI membrane, resulting in the gradual increase of the internal resistance of the battery and the continuous decrease of the discharge capacity of the battery.

3. Shortened cycle life

The water content is too large, which destroys the SEI film of the battery, the internal resistance gradually increases, the discharge capacity of the battery becomes smaller and smaller, the use time of the battery becomes shorter and shorter after each full charge, the number of charging and discharging (cycles) of the battery that can be used normally will naturally decrease, and the service time (life) of the battery will be shortened.

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