Hazards of overcharging and overdischarging of lithium batteries

Lithium batteries are widely used in modern electronic devices, and their advantages include high energy density, long cycle life and low self-discharge rate. However, the use of lithium batteries requires special care, because both overcharging and overdischarging can cause serious damage to the battery.

1. Hazards of overcharging

Overcharging refers to the voltage of the battery exceeding its maximum allowable charging voltage when it is charged. For lithium-ion batteries, it should not usually exceed 4.20V. The hazards of overcharging include:

- Heat and gas generation: Overcharging can cause excessive heat and gas to be generated inside the battery, resulting in increased pressure inside the battery.

- Battery expansion or rupture: If the pressure is too high, the battery may swell or even rupture, causing damage or failure of the battery.

- Electrolyte decomposition: Overcharging can also cause electrolyte decomposition, further exacerbating the chemical reaction inside the battery.

- Safety hazards: In extreme cases, overcharging may cause the battery to catch fire or explode, posing a safety hazard.

2. Hazards of overdischarge

Overdischarge refers to the battery continuing to discharge even when the voltage drops below the rated voltage during the discharge process. For ternary lithium batteries, the rated voltage is generally 3V. The hazards of overdischarge include:

- Battery capacity reduction: Overdischarge will cause irreversible changes in the structure of the active materials inside the battery, so that even if it is recharged, the battery capacity will be significantly reduced.
- Increased battery internal pressure: Overdischarge will increase the internal pressure of the battery and destroy the intersection of the positive and negative active materials.
- Electrolyte dissolution: Overdischarge may also cause electrolyte dissolution, further damaging battery performance.
- Increased battery resistance: Overdischarge will cause the internal resistance of the battery to increase, affecting the discharge performance of the battery.

3. How to avoid overcharging and overdischarging

To avoid overcharging and overdischarging of lithium batteries, the following measures can be taken:

- Use batteries with protection circuits: Many lithium batteries are equipped with protection circuits that can automatically cut off the power supply when the battery is overcharged or overdischarged.

- Use a suitable charger: Choosing a charger that matches the battery can effectively prevent overcharging.

- Check the battery status regularly: By regularly checking the battery voltage and capacity, abnormal conditions of the battery can be discovered in time.
- Avoid using the device for a long time: Using the device for a long time may cause the battery to be over-discharged, so it is recommended to charge it in time when the battery power is low.

Conclusion

Overcharging and over-discharging of lithium batteries will cause serious damage to the battery, affecting its performance and life, and may even cause safety issues. By taking appropriate precautions, overcharging and over-discharging of lithium batteries can be effectively avoided, thereby extending the battery life and ensuring its safe use.