Analysis of and solutions to routine lithium-ion battery(cooling fan jacket battery)problems

In view of the fact that lithium-ion battery accidents occur frequently and constantly in our daily life, we would like to improve your convenience by specially arranging the analysis of causes and solutions for common problems of lithium-ion batteries.

Lithium-ion batteries(cooling fan jacket battery)

1. inconsistent voltage and low individual voltage

1. low voltage due to high self-discharge

Due to high self-discharge of the core, the voltage drop is faster than others, and the voltage drop can be eliminated by storing the voltage after detection.

2. low voltage due to uneven charging

Charging the cooling fan jacket battery after testing results in uneven charging of the core due to contact resistance or charging current mismatch in the detection cabinet. After a short storage period (12 hours), there is little difference in the measured voltage, but after a long storage period, the voltage difference becomes larger. This low voltage can be resolved by recharging the cooling fan jacket battery, so there is no quality problem. After charging the battery during production, store it for at least 24 hours and measure the voltage.

2. expansion of lithium-ion batteries

1. lithium-ion batteries expand when charging

When charging a lithium-ion cooling fan jacket battery, the battery naturally expands, usually by 0.1 mm or less, but overcharging causes the electrolyte to decompose, increasing the internal pressure and causing the lithium-ion battery to expand.

2. swell during processing

Typically, abnormal handling (short circuit, overheating, etc.) causes the electrolyte heated internally to decompose and the lithium-ion battery to swell.

3. expansion during cycling

Battery thickness increases with the number of cycles, but stops after 50 weeks. At 0.3≤0.6 mm, the normal growth of the aluminum shell is more severe and is caused by normal battery reactions. However, increasing the shell thickness or reducing the internal material can adequately reduce the expansion phenomenon.

(iii) Internal resistance is too large

1. different test equipment

If the detection accuracy is not sufficient or contact force groups cannot be eliminated, the internal resistance of the display is too large. Internal resistance meter test should be conducted using the AC bridge method principle. Excessively long storage period.

Excessive storage of lithium-ion batteries leads to excessive capacity loss, internal passivation, and changes in internal resistance, which can be resolved by charge and discharge activation.

2. internal resistance due to abnormal heat generation

Abnormal heat generation in batteries is caused by thermal closure of the diaphragm due to machining of the iron core (spot welding, ultrasonic, etc.), resulting in an increase in internal resistance.

4. battery explosion

Battery explosion usually occurs as follows: 1.

1. explosion

If the protection circuit becomes uncontrollable or the sensing cabinet becomes uncontrollable, the charging voltage exceeds 5 V, the electrolyte decomposes, the battery's internal reactions intensify, the battery's internal pressure rises rapidly, and the battery explodes.

2. overcurrent explosion

Protection circuit or detection cabinet goes out of control, charging current is too large and lithium ions are inserted, metallic lithium forms on the electrode surface, penetrates the diaphragm, and causes positive and negative electrodes to directly short circuit and explode (rare).

3. explosion during ultrasonic welding of plastic shells

When the plastic case is ultrasonically welded, the device transfers ultrasonic energy to the battery core. The ultrasonic energy melts the diaphragm inside the cooling fan jacket battery, directly shorting the positive and negative electrodes and causing an explosion.

Explosion during spot welding

During the spot welding process, an internal short circuit can explode due to overcurrent. Additionally, during the spot welding process, the positive connecting plate is directly connected to the negative electrode, causing the positive and negative electrodes to directly short-circuit and then explode.

5. explosion

The cooling fan jacket battery over-discharge or over-current discharge (>3C) often causes the negative copper foil to melt and deposit on the separator, resulting in a direct short circuit between the positive and negative electrodes and an explosion (rare).