With the rapid development of science and technology, the scope of use and role of lithium batteries has long been self-evident. However, in our daily life, lithium battery accidents always appear, which has always plagued us.
Ⅰ. The voltages of lithium batteries are inconsistent
1. Large self-discharge and low voltage: The self-discharge of the battery is large, making its voltage drop faster than other batteries. The low voltage can be eliminated by checking the voltage after storage.
2. Uneven charging will lead to low voltage: when charging the lithium battery, due to the inconsistent charging current of the lithium battery in the contact resistance or the test cabinet, the charging of the core wire is not uniform. When stored, the voltage difference is large.
Ⅱ. The internal resistance of lithium batteries is too large
1. Due to differences in testing equipment: If the detection accuracy is not enough or the contact groups cannot be eliminated, the internal resistance of the display will be too large, and the principle of the AC bridge method should be used to test the internal resistance meter.
2. Too long storage time: Lithium battery storage time is too long, resulting in excessive capacity loss, internal passivation, and increased internal resistance, which can be solved by charging and discharging activation.
3. Abnormal heating will lead to large internal resistance: the processing of battery cells (spot welding, ultrasonic wave, etc.) will cause abnormal heating of the battery, resulting in the heat sealing of the diaphragm, and the internal resistance will be greatly increased.
Ⅲ. The expansion of lithium batteries
1. Lithium battery expansion during charging: When the lithium battery is charged, the lithium battery will naturally expand, but generally it will not exceed 0.1mm, but overcharging will cause the electrolyte to decompose, the internal pressure will increase, and the lithium battery will expand.
2. Expansion during processing: Usually abnormal handling (such as short circuit, overheating, etc.) causes the internally heated electrolyte to decompose, and the lithium battery expands.
3. Swelling while cycling: When the lithium li ion battery is cycled, the thickness will increase with the number of cycles, but will not increase after more than 50 weeks.
The normal increase is generally 0.3~0.6 mm, and the aluminum case is more serious. This phenomenon is caused by the normal battery reaction. However, if the thickness of the case is increased or the internal material is reduced, the swelling phenomenon can be appropriately reduced.
Ⅳ. Power outage after spot welding of lithium batteries
The voltage of the aluminum shell battery after spot welding is lower than 3.7V, usually because the spot welding current is too large, the internal diaphragm of the battery is ruptured and short-circuited, causing the voltage to drop too fast. Usually caused by incorrect spot welding position.
The correct spot welding position of the lithium battery should be spot welding at the bottom or the side marked with "A" or "-", and the unmarked side and large face cannot be spot welded.
In addition, the weldability of spot welding nickel tape is too poor, so high current spot welding must be used to make the inner high temperature resistant tape not work, resulting in short circuit inside the battery cell.
Ⅴ. The explosion of lithium batteries
1. Overcharge explosion: The control circuit is out of control or the detection cabinet is out of control, so the charging voltage is greater than 5V, resulting in the decomposition of the electrolyte, the violent reaction inside the battery, the rapid increase in the internal pressure of the battery, and the explosion of the battery.
2. Overcurrent explosion: The protection circuit is out of control or the detection cabinet is out of control. Because the charging current is too large, the lithium li ion battery is inserted too late, lithium metal is formed on the surface of the pole shoe, penetrates the diaphragm, and the positive and negative electrodes are directly short-circuited - causing an explosion (rarely occurs). ).
3. Explosion during spot welding: Excessive current during spot welding will lead to serious internal short-circuit explosion. In addition, during the spot welding process, the positive connector is directly connected to the negative electrode, so that the positive and negative electrodes are directly short-circuited and exploded.
4. Excessive explosion: The overdischarge or overcurrent discharge (above 3C) of the lithium battery is easy to dissolve, and the negative electrode copper foil is deposited on the separator, resulting in a short circuit of the positive and negative electrodes and an explosion (rarely).
5. Explosion when the vibration drops: When the battery vibrates violently or falls, the internal pole pieces of the battery are misaligned, resulting in a direct short circuit and explosion (rarely).
Ⅵ. Improper handling of lithium batteries
1. Forcibly moving the positive connection point of the spot welding will lead to poor contact of the positive electrode of the battery, resulting in an increase in the internal resistance of the battery.
2. The spot welding connector is not welded firmly, the contact resistance is large, and the internal resistance of the battery is large.
In short, when choosing lithium battery products, you must choose a professional lithium battery manufacturer, and high-quality lithium battery products can effectively avoid problems.