With the rapid development of science and technology, the scope and role of lithium batteries have long been self-evident. However, in our daily life, lithium battery accidents are always emerging and they are always plagued by us. In view of this, Xiaobian has specially organized lithium. Cause analysis of ion common problems and solutions, I hope to provide convenience for everyone.
First, the voltage is inconsistent and the individual is low
1. Low self-discharge voltage
The self-discharge of the battery cell makes its voltage decrease faster than others. The low voltage can be eliminated by storing the post-check voltage.
2. Uneven charging causes low voltage
After the battery is detected, the battery is not charged due to the inconsistency of the contact resistance or the detection cabinet charge current. The difference in the measured voltage during the short-term storage (12 hours) is small, but the voltage difference is large during long-term storage. This type of low voltage has no quality problems and can be solved by charging. After storage, it is stored for over 24 hours to measure the voltage.
Second, the internal resistance is too large
1. Detecting device differences
If the detection accuracy is not enough or the contact group cannot be eliminated, the internal resistance of the display will be too large. The principle of AC bridge method should be used to test the internal resistance instrument.
2. Long storage time
Lithium batteries are stored for too long, resulting in excessive capacity loss, internal passivation, and increased internal resistance, which can be solved by charging and discharging.
3. Abnormal heat caused by large internal resistance
The battery is abnormally heated during processing (spot welding, ultrasonics, etc.), causing the diaphragm to thermally close and the internal resistance to increase.
Third, lithium battery expansion
1. Lithium battery expands when charging
When the lithium battery is being charged, the lithium battery will naturally expand, but generally it does not exceed 0.1mm, but overcharge will cause the electrolyte to decompose, the internal pressure increases, and the lithium battery expands.
2. Expansion during processing
In general, abnormal processing (such as short-circuit, overheating, etc.) causes excessive internal electrolyte decomposition, lithium battery expansion.
3. Expansion during circulation
When the battery is circulated, the thickness will increase with the number of cycles, but it will not increase after more than 50 weeks. The normal increase is 0.3~0.6 mm. The aluminum shell is more serious. This phenomenon is caused by the normal battery reaction. If you increase the thickness of the shell or reduce the internal material can properly reduce the expansion phenomenon.
Fourth, the battery has lost power after spot welding
The voltage of the aluminum shell core after spot welding is lower than 3.7V, generally because the spot welding current has roughly broken down the internal diaphragm of the core and caused the voltage to drop too quickly.
Normally, the spot welding position is incorrect. The correct spot welding spot should be spot welded on the bottom or marked with 'A' or '—'. No logo on the side and large side can not be spot welded. Others are spot welding nickel tape. Solderability is poor, so it is necessary to use a large current spot welding, resulting in internal high-temperature tape can not work, resulting in internal short circuit cell.
The battery power loss after spot welding is also partly due to the self-discharge of the battery itself.
Fifth, battery explosion
Battery explosion generally occurs in the following situations:
Overcharge explosion
Loss of control of the protection circuit or loss of control cabinet detection causes the charging voltage to be greater than 5V, causing decomposition of the electrolyte, violent reaction inside the battery, rapid rise in battery internal pressure, and explosion of the battery.
2. Overcurrent explosion
Loss of control of the protection circuit or loss of control cabinet detection causes excessive charging current to cause lithium ions to be too late to be embedded, and lithium metal is formed on the surface of the pole piece to penetrate the diaphragm. Positive and negative poles short-circuit directly to cause explosion (infrequently occur).
3. Explosion when ultrasonic welding plastic shell
Ultrasonic welding plastic case, due to equipment reasons to make ultrasonic energy transfer to the battery core, the ultrasonic energy is so large that the battery internal diaphragm melting, positive and negative direct short circuit, resulting in an explosion.
4. Explosion when spot welding
The excessive current during spot welding causes a serious internal short circuit to cause an explosion. In addition, the positive electrode connecting piece is directly connected to the negative electrode during spot welding, so that the positive and negative electrodes are directly short-circuited and then exploded.
5. Excessive explosion
Battery over-discharge or over-current discharge (3C or more) The negative electrode copper foil is easily dissolved and deposited on the separator so that positive and negative electrodes can be directly short-circuited to cause explosion (rarely occurs).
6. Explosion when vibration falls
When the battery is violently vibrated or dropped, the inner pole of the battery is misaligned and directly short-circuited and exploded (rarely occurs).
Sixth, battery 3.6V platform is low
1. The test platform is low due to inaccurate sampling or detection cabinet instability.
2. Low platform due to low ambient temperature (discharge platform is greatly affected by ambient temperature)
Seven, caused by improper processing
(1) Forcefully moving the spot welding anode connecting piece causes poor contact of the positive electrode of the cell, so that the resistance of the cell is large.
(2) Spot welding joints are not welded securely, and the contact resistance is large, so that the internal resistance of the battery is large.
