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Analysis of common problems and solutions of lithium batteries
- Jun 19, 2018 -

With the rapid development of science and technology, the scope and role of lithium batteries have long been self-evident, but in our daily lives, lithium battery accidents are always emerging and we are always troubled. In view of this, lithium ions are listed in this article. Analysis of battery common problems and solutions.

1. The voltage is inconsistent, individual low

a) Low self-discharge voltage

The self-discharge of the battery core makes its voltage decrease faster than others, and the voltage can be eliminated by storing the post-check voltage.

b) Uneven charging causes low voltage

After the battery is detected, when the battery is charged, the battery is not uniformly charged due to the inconsistent contact resistance or the detection cabinet charge current. In the short-term storage (12 hours) the voltage difference is very small, but the long-term storage voltage difference is large, this low voltage and no quality problems can be solved by charging. After storage in the production of stored voltage over 24 hours.

2. The internal resistance is too large

a) 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. Therefore, the principle of AC bridge method should be used to test the internal resistance instrument.

b) Store too long

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.

c) Abnormal heat caused by large internal resistance

In the processing (spot welding, ultrasonic, etc.) of the battery core, the battery is abnormally heated, so that the diaphragm generates a thermal closing phenomenon, and the internal resistance is greatly increased.

Lithium battery expansion.jpgLithium battery explosion.jpg

3. Lithium battery expansion

a) Lithium battery expands when charging

When the lithium battery is being charged, the lithium battery will naturally expand, but generally it does not exceed 0.1 mm, but the overcharge will cause the electrolyte to decompose, the internal pressure increases, and the lithium battery expands.

b) Expansion during processing

In general, abnormal processing (such as short-circuit, overheating, etc.) occurs, and internal electrolyte is too hot to decompose and the lithium battery expands.

c) Expansion during cycling

When the battery is circulated, the thickness will increase with the number of cycles, but it will not increase after more than 50 weeks. Generally, the normal increase is 0.3~0.6 mm. The aluminum shell is more serious. This phenomenon is caused by the normal battery reaction. However, if you increase the thickness of the shell or reduce the internal material, you can properly reduce the expansion phenomenon.

4. 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, causing the voltage to drop too quickly.

Normally, the spot welding position is incorrect, and the correct spot welding spot should be spot welded on the bottom or marked with “A” or “—”. No logo on the side or large side can not be spot welded. In addition, some spot welding nickel strips are poor in weldability, so they must be used for spot welding of a large current, so that the internal high-temperature tape cannot work, causing an internal short circuit in the battery core.

The battery power loss after spot welding is also partly due to the self-discharge of the battery itself.

5. Battery explosion

Battery explosion generally occurs in the following situations:

a) 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 increase in the internal pressure of the battery, and explosion of the battery.

b) Overflow explosion

If the protection circuit is out of control or the control cabinet is out of control, the charging current is so large that lithium ions are too late to embed, and lithium metal is formed on the surface of the pole piece, penetrating the diaphragm, and the positive and negative poles short-circuit directly to cause explosion (infrequently).

c) Explosion when ultrasonic welding plastic shell

Ultrasonic welding of plastic shell, due to equipment reasons to make ultrasonic energy transfer to the battery core, ultrasonic energy is very large so that the battery internal diaphragm melting, positive and negative direct short circuit, resulting in an explosion.

d) Explosion when spot welding

The excessive current during spot welding causes serious internal short circuit explosion. In addition, the positive connection piece is directly connected to the negative electrode during spot welding, and the positive and negative electrodes are directly short-circuited and then exploded.

e) Overexplosive

Battery over-discharge or over-current discharge (3C or more) makes it easy for the negative electrode copper foil to be dissolved and deposited on the separator so that positive and negative electrodes can be directly short-circuited to cause explosion (infrequently).

f) 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).

6.Battery 3.6V platform is low

a) Inadequate sampling of the detection cabinet or instability of the detection cabinet results in a low test platform.

b) Low ambient temperature causes the platform to be low (discharge platform is greatly affected by ambient temperature)

7. Inadequate processing

a) Forcefully moving the spot welding anode connecting piece causes poor contact of the positive electrode of the battery core, so that the internal resistance of the battery core is large.

b) The spot welding joints are not welded well, and the contact resistance is large, so that the internal resistance of the battery is large.