Lithium ion common problem analysis and solution

With the rapid development of technology, the scope and role of lithium batteries have long been self-evident, but in our daily life, the problem of lithium battery accidents is always endless, which is always plaguing us. In view of this, Xiaobian specially sorted out lithium. I think the reasons for the common problems of ions and the solutions are expected to be convenient for everyone.

First, the voltage is inconsistent, the individual is low

1. Self-discharge leads to low voltage

The self-discharge of the battery core makes the voltage drop faster than others, and the low voltage can be eliminated by detecting the voltage after storage.

2. Uneven current causes low voltage

When the battery is tested and charged, the cell is not uniformly charged due to the contact resistance or the inconsistent charging current of the test cabinet. In the short-term storage (12 hours), the voltage difference is small, but the voltage difference is large when stored for a long time. This low voltage has no quality problem and can be solved by charging. Store the voltage for 24 hours after charging in production.

Second, the internal resistance is too large

1. Detection equipment difference caused

If the detection accuracy is not enough or the contact electric power group cannot be eliminated, the internal resistance of the display will be too large. The internal resistance instrument test should be tested by the principle of the AC bridge method.

2. Storage time is too long

Lithium batteries are stored too long, resulting in excessive capacity loss, internal passivation, and increased internal resistance, which can be solved by charge and discharge activation.

3. Abnormal heat caused by internal resistance

The battery is processed (spot welding, ultrasonic, etc.) to abnormally heat the battery, causing the diaphragm to thermally close and the internal resistance is seriously increased.

Third, lithium battery expansion

1. Lithium battery expands when charging

When the lithium battery is being charged, the lithium battery naturally expands but generally does not exceed 0.1 mm, but overcharging causes the electrolyte to decompose, the internal pressure increases, and the lithium battery expands.

2. Expansion during processing

Generally, processing abnormalities (such as short circuit, overheating, etc.) occur, causing internal heat to be excessively decomposed by the electrolyte and the lithium battery to expand.

3. Expansion during circulation

When the battery is circulating, 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, and the aluminum shell is more serious. This phenomenon is caused by normal battery reaction. However, if the thickness of the casing is increased or the internal material is reduced, the expansion phenomenon can be appropriately reduced.

Fourth, the battery has a power failure after spot welding

The voltage of the aluminum shell after spot welding is lower than 3.7 v. Generally, the spot welding current is too short to cause the internal diaphragm of the battery to break down, causing the voltage to drop too fast.

Generally, the spot welding position is incorrect. The correct spot welding position should be spot welded at the bottom or marked with “A” or “-”, the unmarked side and large surface cannot be spot welded. In addition, some of the spot-welded nickel strips have poor solderability, so large current spot welding must be used, so that the internal high-temperature resistant tape does not work, causing internal short-circuiting of the cells. The battery power loss after spot welding is also partly due to the large self-discharge of the battery itself.

Five, battery explosion

There are several situations in which a battery explosion occurs:

1. Overcharge explosion

If the protection circuit is out of control or the detection cabinet is out of control, the charging voltage is greater than 5 v, causing the electrolyte to decompose, the internal reaction of the battery reacts violently, the internal pressure of the battery rises rapidly, and the battery explodes.

2. Overcurrent explosion

If the protection circuit is out of control or the control cabinet is out of control, the charging current is too large, so that the lithium ions are not embedded, and lithium metal is formed on the surface of the pole piece, penetrating the diaphragm, and the positive and negative electrodes are directly short-circuited to cause an explosion (rarely occurring).

3. Ultrasonic welding of the plastic casing when exploding

When the plastic shell is ultrasonically welded, the ultrasonic energy is transferred to the battery core due to the equipment. The ultrasonic energy is so large that the internal diaphragm of the battery is melted, and the positive and negative electrodes are directly short-circuited to cause an explosion.

4. An explosion during spot welding

When the spot welding is too large, the internal short circuit will cause an explosion. In addition, the positive connection 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. Over-explosion

Over-discharge or over-current discharge of the battery (3 c or more) easily causes the negative copper foil to be dissolved and deposited on the separator so that the positive and negative electrodes are directly short-circuited to cause an explosion (rarely occurring).

6. The explosion when the vibration falls

The inner pole piece of the battery core caused by the vibrating or falling of the battery core is dislocated, and the battery is directly short-circuited and explodes (rarely occurs).

Sixth, the battery 3.6 v platform is low

1. The test cabinet is not sampled or the test cabinet is unstable, resulting in a low test platform.

2. The ambient temperature is too low, causing the platform to be low (the discharge platform is greatly affected by the ambient temperature)

Seventh, Improper processing

(1) Forcefully move the spot welding positive electrode connecting the piece to cause poor contact of the positive electrode of the battery core, so that the internal resistance of the battery core is large.

(2) The spot welding tab is not welded firmly, and the contact resistance is large so that the internal resistance of the battery is large.

The page contains the contents of the machine translation.